MESSENGER
MDIS CDR/RDR SOFTWARE INTERFACE SPECIFICATION
Version 1.2.23
Prepared by:
Scott Murchie, Alan Mick, Louise Prockter, and Andrew Rivkin
JHU/APL
Edward Guinness and Jennifer Ward
PDS Geosciences Node
Washington University
Updated March 21, 2017
This document and the archive it describes have been through PDS Peer Review and have been accepted into the PDS archive.
Scott Murchie, MESSENGER Co-Investigator/MDIS, has reviewed and approved this document.
Patricia Garcia, PDS Imaging Node Representative, has reviewed and approved this document.
Susan Ensor, MESSENGER Science Operations Center Lead, has reviewed and approved this document.
DOCUMENT CHANGE LOG
Date |
Description |
Sections affected |
UNK |
Initial Draft |
All |
2/11/08 |
Reformatted and updated, JW & SM |
All |
4/29/08 |
Updated description of data quality index Updated description of pivot-related keywords Updated description of shifting of image due to pixel binning |
All |
11/19/08 |
Updated description of pivot-related keywords Updated description of CDR and DDR labels and keywords Updated CDR and DDR index tables Update filter bandpass descriptions |
All |
2/13/09 |
Updated keywords in Table 3-3 |
Table 3-3 |
9/3/09 |
Updated keywords as result of flight software update. Added description of geographic distribution of BDRs Added description of directory structure for BDRs Redefined file names for BDRs and MDRs to add tile numbers Added description of stacking order of component images BDRs and MDRs Updated index table |
Sections 2.5 and 3, Appendices B, C, D. |
9/3/09 |
Added OBSERVATION_TYPE, SITE_ID, ORBIT_NUMBER to labels. Updated descriptions of data quality index fields. |
Section 3.3.5, Appendices B, C, D. |
6/10/11 |
Replaced document approvals with document review information. Updated descriptions of number of bits per pixel in EDRs and of values of WVLRATIO. Made additional minor edits. |
Document Review Appendix B |
8/1/11 |
Updated for PDS peer review comments. Updated link to NASAView. Changed formatting of OBSERVATION_TYPE |
Section 4.2, Appendix B |
5/1/12 |
Revised BDR and MDR data product descriptions and labels. Updated CDR sample label. |
Sections 2.4.3, 2.4.4, 2.5.2.3, 3.3.7, 3.3.8, Appendices C, E, F |
5/15/12 |
Added VOLUME_ID information. |
Section 3.3 |
5/16/12 |
Updated document name for Applicable Document 4. Reference Applicable Document 4 for PDS delivery schedule and mission phase definitions. Remove out-of-date mission phase definitions in Appendix K. |
Sections 1.3, 2.5.4 Appendices B, K |
5/22/12 |
Updated description of BDR and MDR tiles, and map projection keywords. Updated BDR and MDR index table columns. |
Sections 2.4.3, 2.4.4, 3.3.7, 3.3.8, Table 3.4 |
Updated description of BDR and MDR tiles. Updated descriptions of browse products. Updated descriptions of OBSERVATION_TYPE |
Sections 2.4.3, 2.4.4, 3.3.7, 3.3.8, 3.3.11, Appendix B |
|
9/28/12 |
Clarified boundaries of MDR and BDR tiles. Descriptions of imaging campaigns and relationships to BDRs and MDRs updated. |
Sections 2.2, 2.3, 2.4 |
11/26/12 |
Descriptions of image stacking orders in BDRs and MDRs updated. Extended mission observation type descriptions updated Contents of CALIB directory updated Description of calibration procedure updated Updated descriptions of MDR and BDR tiles |
Sections 2, 3 |
5/31/13 |
Extended mission 2 observation type descriptions updated Description of 3-color map RDRs (MD3s) added Typos fixed |
Sections 2, 3, Appendix G |
6/12/13 |
Updated file naming convention to reference Ò36.3Ó rule versus Ò27.3Ó rule. |
Section 3.3 |
6/12/14 |
Description of 5-color map RDRs (MP5s) added Description of high-incidence angle map illuminated from the east RDRs (HIEs) added Description of high-incidence angle map illuminated from the west RDRs (HIWs) added Description of low-incidence angle map RDRs (LOIs) added Description of regional targeted mosaics (RTMs) added |
All |
6/12/14 |
Changed ÒExperimental Data RecordÓ to ÒExperiment Data RecordÓ. Made updates to CDR/DDR file naming conventions that were implemented due to spacecraft clock reset. Updated MET descriptions in the MDIS instrument raw parameters. |
1.3, 3.3.5.1, 3.3.6.1, Appendix B |
8/7/14 |
Added MDR to the list of volumes that contain a CALIB directory. |
3.3 |
9/11/14 |
Fixed inconsistencies in instrument description Corrected errors in equations for map projection Clarified various terms Updated descriptions of most map products |
All |
9/18/14 |
Reconciled various versions of document Additional edits based on peer review comments |
All |
9/29/14 |
Added MECURY ORBIT YEAR 4 and MERCURY ORBIT YEAR 5 to list of mission phases Replaced HIE, HIW, LOI, MP5, and RTM labels |
Appendices B, H-L |
9/30/14 |
Fixed minor typos. |
All |
2/1/16 |
Added descriptions of End-of-Operations + 1 year data products including revisions to file structures, calibrations, and photometric corrections |
All |
3/30/17 |
Additional updates. |
All |
3/12/17 |
Added descriptions of End-of-Operations + 2 years data products including revisions to file structures, calibrations, and photometric corrections |
All |
3/16/17 |
Additional updates. |
All |
3/21/17 |
Additional updates. |
All |
1. INTRODUCTION.................................................................................................................... 10
1.1 Purpose and Scope................................................................................................................................................................ 10
1.2 Contents................................................................................................................................................................................... 11
1.3 Applicable Documents and Constraints........................................................................................................................... 11
1.4 Relationships with Other Interfaces................................................................................................................................. 12
2. DATA PRODUCT CHARACTERISTICS AND ENVIRONMENT................................... 12
2.1 Instrument Overview........................................................................................................................................................... 12
2.1.1 Hardware Overview....................................................................................................................................................... 13
2.1.2 Pivot Mechanism........................................................................................................................................................... 14
2.1.3 MDIS Data Compression............................................................................................................................................. 16
2.1.4 Exposure Control........................................................................................................................................................... 18
2.1.5 Optical Design................................................................................................................................................................. 19
2.1.6 Filters................................................................................................................................................................................ 21
2.1.7 Flatfield Non-uniformity.............................................................................................................................................. 22
2.1.8 Dark Columns................................................................................................................................................................ 22
2.1.9 Pixel Shift Due to Pixel Binning................................................................................................................................... 23
2.2 Flyby Imaging Overview.................................................................................................................................................... 23
2.3 Orbital Imaging Overview................................................................................................................................................. 24
2.3.1 Primary Mission (Solar days 1-2)................................................................................................................................ 24
2.3.2 Extended Mission 1 (Solar days 3-4)......................................................................................................................... 26
2.3.3 Extended Mission 2 (Solar day 5 through end of mission in solar day 9)........................................................... 27
2.4 Data Product Overview....................................................................................................................................................... 29
2.4.1 CDRs................................................................................................................................................................................ 29
2.4.2 DDRs................................................................................................................................................................................ 29
2.4.3 BDRs................................................................................................................................................................................ 30
2.4.4 MDRs............................................................................................................................................................................... 30
2.4.5 MD3s................................................................................................................................................................................ 31
2.4.6 MP5s................................................................................................................................................................................ 32
2.4.7 HIEs................................................................................................................................................................................. 32
2.4.8 HIWs................................................................................................................................................................................ 33
2.4.9 LOIs.................................................................................................................................................................................. 33
2.4.10 RTMs............................................................................................................................................................................. 33
2.5 Data Processing..................................................................................................................................................................... 35
2.5.1 Data Processing Level................................................................................................................................................... 35
2.5.2 Data Product Generation.............................................................................................................................................. 36
2.5.3 Data Flow and Transmittal to PDS............................................................................................................................. 42
2.5.4 Transmittal Time Line.................................................................................................................................................. 42
2.6 Standards Used in Generating Data Products................................................................................................................ 42
2.6.1 PDS Standards................................................................................................................................................................ 42
2.6.2 Time Standards.............................................................................................................................................................. 42
2.6.3 Coordinate Systems...................................................................................................................................................... 43
2.6.4 Data Storage Conventions........................................................................................................................................... 43
2.7 Data Validation..................................................................................................................................................................... 43
3. DETAILED DATA PRODUCT SPECIFICATIONS........................................................... 45
3.1 Data Product Structure and Organization..................................................................................................................... 45
3.2 Geometric Elements............................................................................................................................................................. 45
3.3 Archive Volume Structure and Contents......................................................................................................................... 45
3.3.1 Root Directory................................................................................................................................................................ 46
3.3.2 Index Directory.............................................................................................................................................................. 46
3.3.3 Catalog Directory........................................................................................................................................................... 49
3.3.4 Document Directory...................................................................................................................................................... 50
3.3.5 CDR Directory (CDR Volume Only).......................................................................................................................... 50
3.3.6 DDR Directory (DDR Volume Only).......................................................................................................................... 54
3.3.7 BDR Directory (BDR Volume Only).......................................................................................................................... 57
3.3.8 MDR Directory (MDR Volume Only)........................................................................................................................ 61
3.3.9 MD3 Directory (MD3 Volume Only).......................................................................................................................... 65
3.3.10 MP5 Directory (MP5 Volume Only)......................................................................................................................... 69
3.3.11 HIE Directory (HIE Volume Only)........................................................................................................................... 72
3.3.12 HIW Directory (HIW Volume Only)........................................................................................................................ 76
3.3.13 LOI Directory (LOI Volume Only)........................................................................................................................... 79
3.3.14 RTM Directory (RTM Volume Only)....................................................................................................................... 83
3.3.15 Calib Directory............................................................................................................................................................. 86
3.3.16 Geometry Directory..................................................................................................................................................... 89
3.3.17 Extras Directory........................................................................................................................................................... 89
4. APPLICABLE SOFTWARE................................................................................................. 92
4.1 Utility Programs................................................................................................................................................................... 92
4.2 Applicable PDS Software Tools........................................................................................................................................ 93
4.3 Tutorial information........................................................................................................................................................... 93
APPENDIX A. DATA ARCHIVE TERMS............................................................................... 94
APPENDIX B. LABEL AND HEADER DESCRIPTIONS.................................................... 96
APPENDIX C. CDR LABEL................................................................................................... 125
APPENDIX D. DDR LABEL................................................................................................... 129
APPENDIX E. BDR LABEL................................................................................................... 133
APPENDIX F. MDR LABEL................................................................................................... 135
APPENDIX G. MD3 LABEL................................................................................................... 137
APPENDIX H. MP5 LABEL................................................................................................... 139
APPENDIX I. HIE LABEL....................................................................................................... 141
APPENDIX J. HIW LABEL..................................................................................................... 143
APPENDIX K. LOI LABEL...................................................................................................... 145
APPENDIX L. RTM LABEL.................................................................................................... 147
APPENDIX M. ATMEL TH7888A DATA SHEET................................................................ 149
Figure 1-1: MDIS Instrument (exterior view).......................................................................... 10
Table 2-1: MDIS Camera Details............................................................................................ 13
Figure 2-2: MESSENGER Spacecraft Instrument Deck.................................................... 13
Figure 2-3: MDIS Design......................................................................................................... 15
Figure 2-4: Range of motion of the MDIS pivot platform.................................................... 16
Figure 2-5a: MDIS/DPU Real-time Compression flowchart.............................................. 17
Figure 2-5b: MESSENGER Main Processor (MP) image post-processing flowchart... 17
Figure 2-6: Mapping of 12 bits to 8 bits using onboard look-up tables............................ 18
Figure 2-7: Autoexposure algorithm decision tree.............................................................. 19
Figure 2-8: WAC optical layout............................................................................................... 20
Table 2-9: MDIS specifications............................................................................................... 20
Figure 2-10: NAC optical layout............................................................................................. 21
Table 2-11: WAC Filters Specifications................................................................................ 21
Figure 2-12: Non-uniformity due to dust particles............................................................... 22
Figure 2-13: Pixels intended for dark columns, and actual pixels in binned images... 23
Table 2-14: Definitions of MDIS data products.................................................................... 35
Table 2-15: Processing Levels for Science Data Sets....................................................... 36
Table 2-16: Solar irradiance used to convert radiance to units of I/F.............................. 38
Figure 2-17: Sequential processing of EDRs to yield RDRs............................................ 41
Table 3-1: Root Directory Contents........................................................................................ 46
Table 3-2: Index Directory Contents...................................................................................... 47
Table 3-3: CDR/DDR Index Table Contents........................................................................ 48
Table 3-4: BDR/MDR/MD3/MP5/HIE/HIW/LOI/RTM Index Table Contents.................... 49
Table 3-5: Catalog Directory Contents.................................................................................. 49
Table 3-6: Document Directory Contents............................................................................. 50
Table 3-7: Filter numbers and their bandpasses................................................................. 51
Table 3-8. MDIS-specific values for CDR label keywords................................................. 54
Table 3-9. MDIS-specific values for DDR label keywords................................................. 57
Table 3-10. Latitude and longitude limits of Mercury Charts.............................................. 58
Table 3-11. MDIS-specific values for BDR label keywords............................................... 61
Table 3-12. MDIS-specific values for MDR label keywords............................................... 65
Table 3-13. MDIS-specific values for MD3 label keywords............................................... 69
Table 3-14. MDIS-specific values for MP5 label keywords................................................ 72
Table 3-15. MDIS-specific values for HIE label keywords................................................. 75
Table 3-16. MDIS-specific values for HIW label keywords................................................ 79
Table 3-17. MDIS-specific values for LOI label keywords.................................................. 83
Table 3-18. MDIS-specific values for RTM label keywords............................................... 86
Table 3-19: Calib Directory Contents.................................................................................... 89
ACRONYMS AND ABBREVIATIONS
ACT |
Applied Coherent Technology Corporation |
APL |
The Johns Hopkins University Applied Physics Laboratory |
ASCII |
American Standard Code for Information Interchange |
BDR |
Map Projected Basemap Reduced Data Record |
BP |
Bandpass |
BW |
Bandwidth |
CCD |
Charge-Coupled Device |
CDR |
Calibrated Data Record |
CODMAC |
Committee on Data Management and Computation |
DDR |
Derived Data Record |
DN |
Data Number |
DPU |
Data Processing Unit |
DVD |
Digital Video Disc |
e |
Emergence angle of reflected light, relative to local surface normal |
EDR |
Experiment Data Record |
FOV |
Field-of-view |
FPGA |
Field-programmable Gate Arrays |
FTP |
File Transfer Protocol |
FWHM |
Full Width at Half Maximum |
g |
Phase angle of reflected sunlight measured at MDIS |
HIE |
Map Projected High-incidence Angle Basemap Illuminated from the East RDR |
HIW |
Map Projected High-incidence Angle Basemap Illuminated from the West RDR |
IAU |
International Astronomical Union |
i |
Incidence angle of solar illumination, relative to local surface normal |
I/F |
Intensity divided by flux, or the ratio of radiance to incident solar irradiance |
IFOV |
Instantaneous field-of-view |
ISO |
International Standards Organization |
JHU/APL |
The Johns Hopkins University Applied Physics Laboratory |
JPL |
Jet Propulsion Laboratory |
LOI |
Map Projected Low-incidence Angle Basemap Reduced Data Record |
MASCS |
MESSENGER Mercury Atmospheric and Surface Composition Spectrometer |
MESSENGER |
MErcury, Surface, Space ENvironment, GEochemistry, and Ranging |
MDIS |
MESSENGER Mercury Dual Imaging System |
MD3 |
Map Projected Multispectral Reduced Data Record (3-Color) |
MDR |
Map Projected Multispectral Reduced Data Record (8-Color) |
MET |
Mission Elapsed Time |
MLA |
MESSENGER Mercury Laser Altimeter |
MOC |
Mission Operations Center |
MP |
Main Processor |
MP5 |
Map Projected Multispectral Reduced Data Record (5-Color) |
NAC |
Narrow Angle Camera |
NAIF |
Navigation and Ancillary Information Facility |
NASA |
National Aeronautics and Space Administration |
OCF |
Optical Calibration Facility |
PCK |
Planetary Constant Kernel (SPICE) |
PDS |
Planetary Data System |
PNG |
Portable Network Graphics (file format) |
RDR |
Reduced Data Record |
RTM |
Map Projected Regional Targeted Mosaic Reduced Data Record |
SIS |
Software Interface Specification |
SOC |
Science Operations Center |
SNR |
Signal-to-noise Ratio |
SQL |
Structured Query Language |
SPICE |
Spacecraft Planet Instrument C-matrix Events; a set of data formats for spacecraft ephemeris, attitude, and instrument pointing |
SSR |
Solid State Recorder |
TBD |
To Be Determined |
UTC |
Coordinated Universal Time |
WAC |
Wide Angle Camera |
This Software Interface Specification (SIS) describes the organization and contents of the MESSENGER Mercury Dual Imaging System (MDIS) Calibrated Data Record (CDR) and Reduced Data Record (RDR) archive. This archive includes data from the two cameras onboard the MESSENGER spacecraft: the Wide Angle Camera (WAC) and the Narrow Angle Camera (NAC) (see Figure 1-1 below). The MDIS CDR/RDR data products are deliverable to the Planetary Data System (PDS) and the scientific community that it supports. All data formats are based on the PDS standard.
Figure 1-1: MDIS Instrument (exterior view).
There are ten MDIS data sets defined in this SIS document. These include:
1) Calibrated Data Records (CDRs)
2) Derived Data Records (DDRs)
3) Map Projected Basemap Reduced Data Records (BDRs) containing a global 750-nm mosaic illuminated for morphology, with a typical solar incidence angle near 74¡ (BDRs)
4) Map Projected Multispectral Reduced Data Records (MDRs) containing an 8-color global map illuminated at a minimized solar incidence angle
5) Map Projected Multispectral Reduced Data Records (MD3s) containing a 3-color regional map illuminated at a minimized solar incidence angle
6) Map Projected Multispectral Reduced Data Records (MP5s) containing a 5-color regional map of the northern hemisphere illuminated at a minimized solar phase angle
7) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at high solar incidence angle from the east, to accentuate low relief morphology (HIEs)
8) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at high solar incidence angle from the west, to accentuate low relief morphology (HIWs)
9) Map Projected Basemap Reduced Data Records containing a global 750-nm mosaic illuminated at a minimized solar incidence angle, to accentuate albedo variations (LOIs)
10) Map Projected Regional Targeted-observation Mosaics containing one or more NAC or WAC frames pointed at a high science priority region of interest (RTMs)
These data sets are defined in section 2.4 and described in more detail in sections 3.3.5 through 3.3.14 of this document.
This SIS is useful to those who wish to understand the format and content of the MDIS data products and ancillary support data. The SIS applies to the MDIS CDR/RDR data products produced during the course of MESSENGER preflight calibration and mission operations. The users for whom this SIS is intended are the scientists who will analyze the data, including those associated with the MESSENGER Project and those in the general planetary science community.
This Data Product SIS describes how data products generated by the MESSENGER team are processed, formatted, labeled, and uniquely identified. The document details standards used in generating the products and software that may be used to access the products. Data product structure and organization is described in sufficient detail to enable a user to read the product. Finally, an example of each product label is provided.
This MDIS CDR/RDR SIS is responsive to the following documents:
Data products described in this SIS are produced by the MESSENGER Science Operations Center (SOC). Changes to the SOC processing algorithms may cause changes to the data products and, thus, this SIS. The MDIS CDR/RDR products are derived from MDIS Experiment Data Record (EDR) products. As such, changes to the EDR product may affect the CDR/RDR products. Changes in MDIS data products or this SIS may affect the design of the MDIS archive volumes.
The Wide Angle Camera (WAC) has 12 band pass filters, while the Narrow Angle Camera (NAC) is monochromatic (has a single filter). Table 2-1 summarizes relevant parameters for both the WAC and NAC cameras. The CDR format for each camera is identical.
|
Narrow Angle Camera (NAC) |
Wide Angle Camera (WAC) |
Field of View |
1.5 degree |
10.5 degree |
Scan Range |
-40¼ to +50¼ from spacecraft +z |
-40¼ to +50¼ from spacecraft +z |
Exposure Time |
1 to 9989 ms |
1 to 9989 ms |
Frame Transfer Time |
3.4 ms |
3.4 ms |
Image Readout Time |
1 s |
1 s |
Spectral Filters |
1 |
12 positions |
Focal Length |
550 mm |
78 mm |
Collecting Area |
462 mm2 |
48 mm2 |
Detector- TH7888A |
CCD 1024 x 1024, 14 µm pixels |
CCD 1024 x 1024, 14 µm pixels |
Pixel FOV |
5.1 m at 200 km altitude |
35.8 m at 200 km altitude |
Table 2-1: MDIS Camera Details.
Most of the MESSENGER instruments are fixed-mounted (Figure 2-2), so that coverage of Mercury is obtained by spacecraft motion over the planet. The imaging system uses a pivot platform to accommodate flyby imaging and optical navigation, as well as imaging during the orbital phase.
Figure 2-2: MESSENGER Spacecraft Instrument Deck.
The full MDIS instrument includes the pivoting dual camera system as well as the two redundant external Data Processing Units (DPUs). The dual camera assembly without the DPUs is usually simply referred to as ÒMDIS.Ó The overall design and look of MDIS, shown in Figure 2-3, was driven by mass limitations, the severe thermal environment at Mercury, and the requirement for a large field-of-regard for optical navigation and off-nadir pointing. The total mass of MDIS is 8.32 kg, including flight blankets, harness to DPU, and thermal gasket.
The pivot platform houses the multispectral WAC and the monochrome NAC. The thermal design generally maintained the CCD detectors in the WAC and NAC within their desired operating temperature range of -45¡C to -10¡C; during the hottest parts of Mercury orbit, occasional excursions above this range occurred. Only one DPU may be active at a time, and due to thermal constraints only one camera will operate at a time; however, observations with the two cameras can be interleaved at 5-s intervals. A separate electronics assembly accommodates switching between the various modes of operating with the redundant DPUs. The pivot platform has a large range of motion (~240¡) to allow the cameras to be Òtucked awayÓ to protect the optics from contamination.
The MDIS pivot platform is controlled by a stepping motor (Fig. 2-3). The motor phases are controlled directly by the DPU software to move the platform. The phase pattern can be adjusted by software to move the platform forwards or backwards. The pivot platformÕs range of motion is mechanically constrained by ÒhardÓ stops. The range of motion is further constrained by ÒsoftÓ stops applied by the software. The nominal allowed range is shown in Fig. 2-4. The total range of motion of MDIS is about 240¡, limited by hard mechanical stops in the pivot motor. The hard stops are fixed at -185¼ and 55¼. The pivot motor drive-train provides precision rotation over the 90¡ operational range of motion (Figure 2-4) about the spacecraft +Z axis.
The MDIS pivot actuator is capable of accurately stepping in intervals of 0.01¡ (~150 µrad) per step. Crude pointing knowledge is determined by first ÒhomingÓ the instrument, which is accomplished by driving the actuator into one of the mechanical hard stops for a period of time sufficient to ensure the orientation of the instrument if it had been previously stopped at the opposite extreme of travel. The rotational speed of the pivot platform is 1.1¡/s. Once the location of the pivot actuator is known, the flight software retains this knowledge and subsequent pointing commands are achieved by counting pulses (steps) to the motor.
There are two alternative measures of pivot position: by counting motor steps following homing, as described above, or by using the position returned from a pivot position resolver. The latter method, augmented by inflight calibration of resolver readings using stellar pointing calibrations, is used for the most accurate determination of pivot pointing for construction of SPICE camera kernels and for production of map products.
Figure 2-4: Range of motion of the MDIS pivot platform. Operational range is -40¡ sunward to +50¡ antisunward (planetward). When stowed, the sensitive first optic of each telescope is protected.
The MESSENGER mission requires compression to meet its science objectives within the available downlink. Figure 2-5 summarizes the compression options available to MDIS at the instrument level and using the spacecraft main processor (MP). At the focal plane, 2×2 binning is available on-chip to reduce the 1024×1024 images to 512×512 format, 12-bit data number (DN) levels can be converted to 8 bits, and data can be compressed losslessly. After data are written to the recorder, they can be uncompressed and recompressed by the MP more aggressively using any of several options: additional pixel-binning, subframing, and lossy compression using an integer wavelet transform. The strategy for MP compression is that most data except flyby imaging are wavelet compressed, typically 4:1 for monochrome data and to a lower ratio (² 4:1) for orbital color data. Color imaging but not monochrome imaging may be further pixel-binned. For the special case of optical navigation images, there is a ÒjailbarÓ option that saves selected lines of an image at a fixed interval for optical navigation images of Mercury during flyby approaches.
Figure 2-5a: MDIS/DPU Real-time Compression flowchart.
Figure 2-5b: MESSENGER Main Processor (MP) image post-processing compression flowchart.
Figure 2-6: Mapping of 12 bits to 8 bits will be accomplished using onboard look-up tables. The tables are designed to preferentially preserve information at different DN ranges, and they can accommodate a nominal detector dark level as well as one that has changed with time. ÒNoiseÓ refers to the read noise, which is ÒlowÓ (1 12-bit DN) for the WAC CCD and ÒhighÓ (2 12-bit DNs) for the NAC CCD. (1) Low noise, high bias SNR proportional. Usage: Typical imaging with varied brightness. Nominal for most imaging. (2) Low noise, high bias DN-weighted SNR proportional. Usage: Faint object imaging. (3) High noise, high bias DN-weighted SNR proportional. Usage: B/W, low brightnesses. Nominal for NAC imaging. (4) Low noise, medium bias SNR proportional. (5) Low noise, medium bias DN-weighted SNR proportional. Usage: Faint objects. (6) High noise, medium bias DN-weighted SNR proportional. Usage: B/W mostly low brightness. (7) Zero-bias SNR proportional. Usage: Typical imaging, varied brightness. (8) Linear. Usage: High brightness mapping, preserves high DN information.
The exposure time of images can be set manually by command or automatically by the software. In manual mode, a full 9989 ms range of exposure times is available. In automatic mode, the exposure time of the next image is computed by the DPU software (Fig. 2-7). This computation has two distinct steps. The first step computes a new exposure time based on the brightness of a test image. The second step anticipates commanded filter wheel motion to a new filter and adjusts the computed exposure time accordingly.
During the read stage of the image pipeline, the hardware generates a histogram of the image. The histogram is analyzed by the software to determine if the image is overexposed or underexposed. First, the histogram is scaled by a factor of four if it comes from a 2×2 binned image. If the brightest histogram value (except for a commandable number of allowable saturated pixels) exceeds a saturation threshold, the image is considered overexposed and the exposure time is scaled back. Otherwise the image is considered underexposed. Histogram values are accumulated starting from the brightest bin down towards the dimmest bin, until the saturation threshold is exceeded. The brightness value that causes the sum to exceed the threshold is the actual image brightness. The exposure time is scaled by the ratio of the commanded target brightness to the actual brightness, after a background brightness is removed. The algorithm is characterized by uploadable parameters for the saturation threshold, allowable number of saturated pixels, overexposure fallback, and background brightness.
The algorithm described so far compensates for changes in scene brightness and filter wheel changes. The next step adjusts the exposure time further if the imager, binning mode, or filter selected for the next exposure does not match what was used in the test exposure. The exposure time is scaled by the ratio of the transmissivity (actually, the expected brightness in DN/s) of the old setup to the transmissivity of the new setup. An uploadable table of transmissivities for the WAC filters and for the NAC imager in either binning mode are used. Finally, the computed exposure time is forced to fall within an uploadable range but is always less than 1 second.
Figure 2-7: Autoexposure algorithm decision tree. A 64-bin histogram is computed in hardware for each image. If an image is determined to be underexposed, the actual exposure is computed as Actual = minimum brightness such that the sum of the pixels above this brightness < saturation threshold.
The WAC (Figure 2-8) consists of a 4-element refractive telescope having a focal length of 78 mm and a collecting area of 48 mm2 (Table 2-9). The detector located at the focal plane is an Atmel (Thomson) TH7888A frame-transfer CCD with a 1024×1024 format and 14-µm pitch detector elements that provide a 179-µrad pixel (instantaneous) field-of-view (IFOV). See Appendix M for the Atmel TH7888A data sheet. A 12-position filter wheel provides color imaging over the spectral range of the CCD detector. Eleven spectral filters spanning the range from 395 to 1040 nm are defined to cover wavelengths diagnostic of different potential surface materials. The twelfth position is a broadband filter for optical navigation and low-light imaging. The filters are arranged on the filter wheel in such a way as to provide complementary passbands (e.g., for 3-color imaging, 4-color imaging) in adjacent positions.
Figure 2-8: WAC optical layout.
|
Narrow Angle |
Wide Angle |
Field of view |
1.5¡ × 1.5¡ |
10.5¡ × 10.5¡ |
Pivot range |
-40¡ to +50¡ |
|
(observational) |
(Sunward) (Planetward) |
|
Exposure time |
1 to 9989 ms |
|
Frame transfer time |
3.4 ms |
|
Image readout time |
1 s |
|
Spectral filters |
1 |
12 positions |
Spectral range |
725Ð783 nm |
395Ð1040 nm in clear filter |
Focal length |
550 mm |
78 mm |
Collecting area |
462 mm² |
48 mm² |
NAC-WAC coalignment knowledge |
<0.01 deg (<179 μrad) |
|
Spacecraft pointing control |
<0.1 deg (<1.75 mrad) |
|
Spacecraft pointing knowledge |
0.02 deg (<350 μrad) |
|
Detector-TH7888A |
CCD 1024×1024, 14-μm pixels |
|
IFOV |
25 μrad |
179 µrad |
Pixel FOV |
5.1 m at 200-km altitude |
35.8m at 200-km altitude |
Quantization |
12 bits per pixel |
|
Compression |
Lossless, multi-resolution lossy, 12-to-8 bits |
Transfer to DPU; transfer from DPU to SSR limited to 3 Mbps (4 s to transfer 1024×1024 image).
Table 2-9: MDIS specifications.
The NAC (Figure 2-10) is an off-axis reflective telescope with an effective 550-mm focal length and a collecting area of 462 mm2. The NAC focal plane is identical to the WACÕs, providing a 25-µrad IFOV. The NAC has a single medium-band filter (50 nm wide), centered at 750 nm to match to the corresponding WAC filter for monochrome imaging.
Figure 2-10: NAC optical layout.
The WAC camera utilizes a twelve position filter wheel with bandpasses from 430 to 1020 nm, including a broadband navigation filter centered at 750 nm. The NAC is a broadband BW imager with a center wavelength of 747 nm and a bandpass of 53 nm. Other than the image dimensions, the data products of each camera are identically formatted. Table 2-9 shows the design-level focal length, collecting area, and field of view for each camera. Table 2-11 shows the calibrated filter wheel position and bandwidth parameters, and the design-level focal lengths for each filter. More accurate values for focal lengths are derived from flight measurements, and are updated over the course of the mission as knowledge of the values improves.
Filter Number |
Filter Filename letter |
Wavelength (Flight) (nm) |
FWHM (Flight) (nm) |
Total Thickness (mm) |
Focal length (mm) |
Scale change (%) |
1 |
A |
698.8 |
5.3 |
6.00 |
78.218 |
-0.104 |
2 |
B |
700 |
600.0 |
6.00 |
78.163 |
-0.104 |
3 |
C |
479.9 |
10.1 |
6.30 |
77.987 |
-0.329 |
4 |
D |
558.9 |
5.8 |
6.30 |
78.023 |
-0.283 |
5 |
E |
628.8 |
5.5 |
6.20 |
78.109 |
-0.173 |
6 |
F |
433.2 |
18.1 |
6.00 |
78.075 |
-0.216 |
7 |
G |
748.7 |
5.1 |
5.90 |
78.218 |
-0.033 |
8 |
H |
947.0 |
6.2 |
5.20 |
78.449 |
0.262 |
9 |
I |
996.2 |
14.3 |
5.00 |
78.510 |
0.340 |
10 |
J |
898.8 |
5.1 |
5.35 |
78.390 |
0.186 |
11 |
K |
1012.6 |
33.3 |
4.93 |
78.535 |
0.372 |
12 |
L |
828.4 |
5.2 |
5.60 |
78.308 |
0.082 |
Table 2-11: WAC Filters Specifications Ð Wavelength and FWHM Measured at -26¡ C.
For WAC spectral filters, bandpass widths were selected to provide required SNR in exposure times sufficiently short to prevent linear smear by along-track motion, yet sufficiently long (>7 ms) to avoid excessive artifacts from removal of frame transfer smear during ground processing. SNR is not an issue, as sufficient light is available for SNRs >200, but saturation is a concern at low phase angles. At the same time, both cameras must be sufficiently sensitive to provide star images for optical navigation. When imaging Mercury against a star background, at least three stars must be visible per image at ³ 7× noise with the clear filter.
Response uniformity, or flat field, is a measure of pixel-to-pixel variations in responsivity. One significant non-uniformity in the data noted during ground calibration is that of dark spots scattered across the FOV of both imagers. The darker spots scattered across WAC images are fixed with respect to the CCD regardless of filter wheel setting, though their intensities do vary slightly with filter. The sizes of the spots are consistent with shadows of <<35-µm dust on the CCD window, and their number density is consistent with the standards for a class-10,000 clean room in which the camera was assembled. Also consistent with this hypothesis, following instrument vibration during environmental testing, the locations of several spots changed. With the exception of a single particle (arrow, Figure 2-12) the dust spots do not significantly affect the DN levels. The spots themselves also moved as the instrument was subjected to the vibrations of launch and flight. The original determination of the flat field was made using images of the interior of an integrating sphere, acquired during ground calibration. Inflight, several iterative improvements of the flat-field correction were performed. Images of an onboard calibration target inside the spacecraft adaptor ring, as well as of the Venus cloud tops acquired during the second Venus flyby, have been used prior to Mercury orbit insertion. After Mercury orbit insertion, medians of thousands of low-contrast field-filling images acquired through each filter provided an improved flat field.
Figure 2-12: Non-uniformity due to dust particles is visible in integrating sphere images acquired through the quartz window in the OCF chamber door of the calibration facility.
Dark models for MDIS images can be created using either (a) dark images (usually acquired with MDIS stowed against the spacecraft deck) or (b) columns lying outside of the CCDÕs active area. In the full-frame mode for either the WAC or NAC, the first four columns of each image are taken from a region of the CCD that is never exposed to light and, thus, represents a dark level that is purely a function of bias and dark current. The dark columns are separated from the image section by five isolation columns to avoid diffusion of signal from the active area. When the image is read out, these four columns are mapped into the first four imaging columns, so the resulting image is a square 1024 by 1024 pixels, with the first four columns replaced with the sampled dark columns. The four dark columns behave identically to the scene as a function of row, exposure time, and temperature to within 0.26 DN.
In the binned mode for both cameras, true dark columns are unavailable due to the pixel-shift problem described in the following section. However, the second column of a binned image provides a much lower response to light than a column in the active image area. This lower-response column does show a temperature- and exposure-time response that can be modeled, making it a functional Òdark.Ó Therefore, the dark column model simply uses the second column of an image (binned or full-frame) to be a representative of the dark strip properties.
Given the problematic nature of binned ÒdarkÓ columns, model (a) above is used as the basis for an analytical model of dark current. Nevertheless, the dark strips could serve as an indicator of the variations of the CCDÕs response to radiation, and, as such, a means to validate the performance of the dark model over time.
For either camera, an error in programming the Actel field-programmable gate arrays (FPGAs) that executes binning at the focal plane results in a different sampling of the CCDs. Binned images are sampled from a part of the CCD that is offset 8 unbinned pixels (4 binned pixels) in the direction of increasing sample number in the image. This difference in pointing is accounted for in the SPICE frames kernel.
Figure 2-13: Pixels intended for dark columns, and actual pixels used in binned images for WAC and NAC.
The MESSENGER trajectory provided three flyby opportunities of Mercury: January 2008, October 2008, and September 2009. During the first flyby, approximately half of the hemisphere not viewed by Mariner 10 was illuminated (subsolar longitude 190¡E); the first Mercury data returned from MESSENGER thus covered new terrain, including the previously unseen western half of the Caloris Basin and its ejecta. During the second flyby, illumination was centered on the eastern edge of the Mariner 10 hemisphere (subsolar longitude 4¡E). The lighting geometry for the third encounter was nearly identical to that of the second encounter with the subsolar point at the prime meridian (0¡E); the approach and departure phase angles were less extreme, however, resulting in better inbound imaging. During the second and third flybys, most of the remaining unseen portion of Mercury was imaged. Total coverage between Mariner 10 and the three flybys excluded only the poles and a small longitudinal gap up to 6¡ wide, centered at 93¡E longitude.
During each of the flybys, three major types of image mosaics were acquired. First, MDIS-NAC raster scan mosaics covered >80% of the planet at a resolution averaging ~500 m/pixel, providing a first version of a global map. Second, MDIS-WAC imaged the planet in 11 filters at as good as ~2.4 km/pixel. Finally, high-resolution WAC and NAC mosaics covered selected areas at higher resolutions.
Creating maps from imaging obtained at various photometric geometries during the flybys and from orbit requires an accurate photometric model of the planet at the wavelengths of the NAC and WAC filters. Therefore, MESSENGER began the collection of multi-geometry photometric characterization of MercuryÕs surface from data acquired during the flybys, through observations of the same point on the ground acquired at the same incidence angle, but different emission and phase angles.
Imaging during the 8 solar day orbital phase is divided into two types, acquired as parts of organized mapping "campaigns", and "targeted observations" covering regions of interest specifically defined by the Science Team. In the latter case the region of interest is recorded by the SITE_ID keyword.
On 18 March 2011 MESSENGER was placed in a highly elliptical orbit with a periapse of 200 km at ~64ûN and an apoapse of 13100 km. The orbit had an approximately 12-hour period, was inclined 80û to the planetÕs equatorial plane, and was not sun-synchronous. During one Mercurian solar day, the orbit precessed completely around the planet twice. At times the groundtrack was near the terminator; 22 days later it passed over the sub-solar point. The following were the major imaging campaigns during the ~1 Earth year primary mission.
One of the primary goals of MDIS is to acquire a global monochrome basemap at ~250-m/pixel average spatial sampling, low emission angle, and moderate incidence angle (45û-80û). For a given area, coverage was first obtained when local nadir was viewed at a solar incidence angles as close as possible to 68¡. This value is a compromise between higher incidence angles to highlight subtle topography and lower incidence angles to eliminate shadows. The choice of the NAC or WAC camera was driven by the necessity of maintaining both cross-track overlap and near uniform spatial resolution: the NAC was used to image the southern hemisphere, whereas the WAC was used in the northern hemisphere. For monochrome imaging, the 750 nm filter was used in the WAC to match the 750 nm bandpass of the NAC. This first global nadir-viewing basemap was acquired during the first Mercurian solar day of the mission (i.e., during the first half of the primary mission).
An off-nadir stereo-complement to the above basemap consists of images taken at nearly the same local solar time one solar day later, with stereo convergence attained using off-nadir pointing up or down the groundtrack. The stereo complement was acquired on solar day two (i.e., the second half of the primary mission).
Color mapping was repeated after the flybys, improving spatial resolution by nearly a factor of 3 to 1.0 km/pixel on average. Images were acquired using near-nadir pointing, but in contrast to the monochrome basemap, low incidence angles were targeted. The data were acquired in only 8 of the 11 filters used during the flybys, to manage data volume. In addition, 2x2 or 4x4 pixel-binning was applied at northern latitudes, also to manage data volume.
In order to identify permanently shadowed (and permanently illuminated) areas, the south polar region was imaged repeatedly throughout each Mercurian solar day during every fourth orbit, so that all longitudes were illuminated at ~5û increments of solar longitude. This strategy provides coverage of all areas near their minimum solar incidence angle, with nearly a full 180¡ range of solar azimuth from local sunrise to local sunset. The campaign was divided between the two solar days. On the first solar day, the WAC was used while the spacecraft was at high altitude at high southern latitude, providing 1.5-1.7 km/pixel image coverage extending equatorward to approximately 60û latitude on the dayside (70¡ latitude with the full azimuth range). On the second solar day a more limited region to 75¡ latitude was covered at about 300 m/pixel using the NAC.
Selected areas mostly in the northern hemisphere, targeted predominantly using flyby imaging, were imaged from orbit at resolutions of typically ~20 m/pixel using strips of NAC images. Pointing was attempted to be at geometries similar to that of the global monochrome basemap. Some strips were re-imaged at an off-nadir geometry to provide stereo convergence. Additional targets were observed, usually off-nadir, at poorer resolutions and with lower incidence angles, simultaneously with measurements from the MASCS/VIRS spectrometer.
Selected regions of the planet were targeted with full-resolution color imaging with spatial sampling typically ~400 m/pixel, but using only 3 color filters. This reduced number of filters was driven by spacecraft velocity, slower cadence of the readout of unbinned images, and the need to maintain overlap between filters. Targets were identified from Mariner 10 data and MESSENGER flyby results.
Orbital photometric observations complement the flyby photometry by repeatedly covering representative areas near the Rembrandt and Beethoven basins at wide variety of incidence, emission, and phase angles, initially using the same 8-color filter set as for the global 8-color map. Images of the same target are taken multiple times, as the planet's rotation varies the incidence angle as the target region moves from the terminator to near the sub-solar longitude. Later in the mission the number of filters was increased to 11 to improve photometric correction of 11-color targeted observations.
Once per week, three sets of 2x1 frame WAC 750-nm image mosaics are acquired at high altitudes, showing the entire limb of Mercury. These data are used to help define the low-order global shape model for Mercury.
Star fields were imaged in the WAC clear filter in coordination with limb imaging, to track temporal drift in MDIS pointing due to plastic deformation of the spacecraft from thermal cycling. In addition, periodically the MDIS pivot plane is pointed off the planet's limb and star images acquired at multiple positions within the gimbal plane that are separated by tens of degrees, and the sequence of positions is repeated over the course of an orbit. This periodic measurement is used to characterize pointing drift due to temperature dependent elastic deformation of the spacecraft structure, as well as to characterize plastic deformation.
In April 2012 MESSENGER executed a series of maneuvers to change the orbit and spend more time at lower altitude. The new 8-hour orbit was still highly eccentric, with MESSENGER travelling between 278 and 10,314 km above Mercury's surface. Imaging campaigns were modified to take advantage of the lower altitude and to optimize illumination and viewing compared to the "general purpose" monochrome basemap and stereo complement from the primary mission. The extended mission comprises Mercury solar days 3 and 4, through the end of March 2013.
One issue from the primary mission stereo map was its "one size fits all" illumination geometry that attempted to meet multiple objectives while being optimized for none. In order to attain stereo coverage with reduced shadows, a new pair of mosaics was acquired that used the camera selection and spatial resolution strategy from the primary mission monochrome basemap, but targeted lower solar incidence angles, 45¡ instead of 68¡. The nadir mosaic was acquired on solar day 3, and the stereo complement on day 4. Gaps in both were filled over time.
To improve mapping and characterization of very low-relief features, an additional mosaic was acquired targeting a higher incidence angle than the primary mission monochrome basemap, 80¡ instead of 68¡. Later, coverage was augmented to provide separate maps illuminated from the east and from the west.
3-color mapping of northern and equatorial latitudes without pixel binning was conducted on solar day 3. This campaign is the equivalent of targeted color imaging from the primary mission, except with spatially continuous coverage with slowly varying illumination geometries.
In order to identify permanently shadowed (and permanently illuminated) areas, during both solar days 3 and 4 imaging of the north polar region was conducted whenever possible to build coverage both at minimum solar incidence angle and with as large as possible a range of solar azimuths.
Beginning in Extended Mission 1, spare downlink was used to acquire non-targeted, high-resolution NAC images of the northern hemisphere, as "ride-along" observations during times when spacecraft pointing is optimized for other instruments.
Targeted, high-resolution NAC strips, color photometry, limb images, and on-orbit calibrations continued to be acquired as during the primary mission. Regular color imaging of the southern polar region began to be used to monitor radiometric performance of the WAC.
At the end of March 2013 MESSENGER began its second extended mission, with new imaging campaigns complementing those of the Primary Mission and Extended Mission 1. The orbit around Mercury remained largely the same initially, but solar perturbations caused the periapse to approach the surface. In December 2013 the first of several low altitude (<200 km) periapse periods occurred. Each was followed by a periapse-raising maneuver. Once propellant was exhausted, the periapse intersected the surface, and active mission operations ended upon spacecraft impact on 30 April 2015. Imaging campaigns provide new regional views, new global views at complementary lighting, high-resolution observations at pixel scales as good as <2 m/pixel in the NAC, low-light imaging of the interiors of permanently shadowed polar craters, color emission phase functions of selected features to investigate small-scale differences in photometric properties, and oblique views of high-relief features to investigate vertical structure of the upper crust. Systematic searches were conducted for Mercurian satellites and for vulcanoid asteroids whose semimajor orbital radii are interior to Mercury.
The high-incidence mapping from Extended Mission 1 included about a dozen large contiguous areas illuminated at high solar incidence angle from either the east or west. During the second extended mission, additional coverage at high solar incidence angle was acquired so that nearly global coverage was attained in two nearly complete, complementary global maps each at high solar incidence angles, one illuminated from the east and the other from the west.
Both the 8-color global map acquired during the Primary Mission and the 3-color map acquired during Extended Mission 1 are mostly nadir-viewing, such that higher latitudes are imaged at higher phase angles. In each polar region, the high phase angles and extended shadows complicate the recognition of color variations. The northern plains surrounding the north pole are the single largest expanse of smooth plains on Mercury, and have a relatively high albedo and red color. These limitations of the 8-color and 3-color maps obscure whether there are multiple color units in the northern plains. To address this question, the northern plains region was imaged in 5 colors at a variable angle off-nadir, to attain a uniform low phase angle near 30¡.
Prior to Extended Mission 2, high-resolution stereo imaging with the NAC was mostly limited to image strips taken far apart in time at complementary geometries, yielding inconsistent stereo convergence. A new approach used control of spacecraft pointing to acquire stereo geometries at two times along the spacecraft groundtrack on a single orbit, providing spatial sampling typically better than 50 m/pixel.
Beginning late in Extended Mission 1 and continuing through Extended Mission 2, the WAC clear filter and long exposures in the NAC were used to image permanently shadowed regions inside high-latitude craters, illuminated indirectly by sunlight reflected from nearby ridges or crater walls. As of mid-2014, 3-color imaging using 560, 750, and 830 nm filters and longer exposure times began on an experimental basis.
Beginning in Extended Mission 2, 11-color targets using the full set of WAC spectral filters were acquired covering regions of interest for their spectral variations, including pyroclastic vents, hollows, and fresh crater materials.
Beginning in Extended Mission 2, 3-color targets using 430-, 750-, and 1000-nm WAC spectral filters at 2 to 5 phase angles were acquired within single orbits or groups of two orbits, to measure spatial differences in photometric properties of targets including pyroclastic vents, hollows, and fresh crater materials.
During Extended Mission 2, "movies" were acquired using the WAC 750-nm filter pointed into the ram direction to capture a view of flying over Mercury's surface at a low altitude.
During Extended Mission 2, high emission angle views of selected high-relief features including massifs, escarpments, pyroclastic vents, and crater interiors were acquired to provide better views of exposures of vertical structure of the shallow crust.
The objective of satellite searches was to observe any satellites close to opposition, when they would be at the largest solar elongation to improve brightness and detectability. Four separate searches were conducted near Mercury perihelion to enhance the brightness of the satellites, each looking northward (ÒupwardÓ from the orbital apoapsis below MercuryÕs south pole) toward the expected orbital plane. During each search, overlapping pointing steps were made, spanning a range from 2Ð75 Mercury radii. The sequence began at the greatest distance, stepped to the smallest, and then stepped back to the largest, allowing faster motion of an inner satellite to be detected (before an object left the field) while still allowing the slower motion of an outer satellite to be detected (because enough time had passed). Multiple images were used at single steps to reject radiation artifacts. Motion expected was due primarily to parallax from the spacecraft motion. The entire sequence was repeated after a fixed time. The combined searches covered ~20% of orbital phase space.
Due to its ability to point to 30¡ from the Sun at Mercury perihelion, MDIS was able to image the outer portion of the vulcanoid zone at 0.18Ð0.21 AU which represents 46% of the volume of the zone where vulcanoids are expected to be most likely. During MESSENGER's cruise phase, vulcanoid searches were conducted six times, collectively covering 46% of the volume of the vulcanoid zone. At each search, MDIS observed one field width north and south of the ecliptic and on both sides of the Sun. This was repeated over three time scales: immediate, to reject artifacts; after a few hours to distinguish motion from stars; and after a few days to attempt to recover an object and estimate an orbit. An altered strategy was used for two final searches from Mercury orbit, allowing detection of smaller bodies at the expense of coverage. These deeper searches were achieved by co-adding images and by making longer strings of sequential observations, thus making any motion much more prominent. Each of these searches covered 5% of the vulcanoid volume.
During Extended Mission 2, an experiment was conducted to attempt to image emissions from Mercury's exosphere, and to measure stellar occultations by Mercury's night-side optically. The latter was a proof-of-concept to demonstrate ability to measure the convex upper high of the seasonally shadowed portion of an asteroid during a spacecraft encounter much shorter than a Mercurian year. WAC clear filter images were acquired in sets of 3 to reject radiation noise, at three positions with the nightside of Mercury filling 0.25, 0.5, and 0.75 of the field of view. Portions of the limb were targeted where illuminated portions of the planet were at least 10¡ from the WAC boresight to minimize scattered light.
High-resolution NAC strips, color photometry, color imaging of the south polar region, limb images, and on-orbit calibrations continued to be acquired as during the first extended mission.
The MDIS archive contains ten volumes of higher-level data products: CDRs, DDRs, BDRs, MDRs, MD3s, MP5s, HIEs, HIWs, LOIs, and RTMs. Each is briefly described below and listed in Table 2-14. More detailed descriptions can be found in sections 3.3.5 through 3.3.14.
The Calibrated Data Record (CDR) data set consists of single-frame calibrated images in units of radiance or I/F, with I/F for WAC images provided as two versions, either corrected or not corrected empirically for time-variable responsivity. CDRs are not geometrically corrected. Versions 1 through 5 represent a series of improvements in accuracy of the radiometric calibration that reduce systematic artifacts. See section 3.3.5 for a more detailed description of the CDRs.
The Derived Data Record (DDR) data set consists of single images that have 5 bands of data as 32-bit PC_REAL or IEEE_REAL: (a) latitude, (b) longitude, and (c) incidence angle, (d) emission angle, and (e) phase angle at the equipotential surface. In version 0 DDRs, latitude and longitude are calculated using the best-determined spacecraft and instrument pointing values, spacecraft position, and camera model recorded in SPICE kernels, and an ellipsoidal model of the planet surface. For version 1 DDRs delivered one year after the end of orbital operations, "smithed" c-kernels that record the time history of pivot pointing and a global digital elevation model (DEM) are used. In the smithed c-kernels used for version 1, pointing history is adjusted to control map projection, to provide improved agreement in the location of geographic features in overlapping NAC and WAC G-filter images. Version 2 DDRs, delivered two years after the end of orbital operations, were constructed for only WAC G-filter images used in multispectral data products (MDRs, MD3s, MP5s). In the smithed c-kernels used for version 2, the usage of only WAC G-filter images optimizes the control of multispectral images, resulting in less "blur" from the averaging procedures described for the newest version of MDRs, MD3s, and MP5s. See section 3.3.6 for a more detailed description of DDRs.
The Map Projected Basemap RDR (BDR) data set consists of a global monochrome map of reflectance corrected to i = 30¼, e = 0¼, g = 30¼ at a resolution of 256 pixels per degree. Version 0, released in 2013, is compiled from images taken as a part of the global monochrome basemap campaign described in section 2.3.1.1. Depending on spacecraft altitude when the data were taken, either the NAC or WAC 750-nm image was used. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (and different from parameters used in map products containing lower-incidence angle data). It uses images that best fit an intended photometric geometry of low emission angle and incidence angle near 68¡. Version 1, released one year after the end of orbital operations, is compiled using NAC or WAC 750-nm images from any campaign that best fit an intended illumination geometry of low emission angle and incidence angle near 74¡. It is controlled and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2 is modified from version 1 by adding latitude-dependence to criteria for including images in the BDRs, and introducing human-in-the-loop selection of images for inclusion and exclusion.
The BDR data set is divided into 54 segments or Òtiles,Ó each representing the NW, NE, SW, or SE quadrant of one of the 13 non-polar quadrangles, plus the 2 polar quadrangles, or ÒMercury chartsÓ already defined by the USGS (see Table 3-10). Latitude boundaries do not match precisely the USGS definition. For this archive, the equirectangular products extend to the shared midpoint latitude rather than include the defined redundant overlap between those products. Each map also contains 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id, (b) BDR metric, a metric used to determine the stacking order of component images Ð which image of all those covering piece of terrain is "on top" (see section 2.5.2.3), (c) solar incidence angle, (d) emission angle, and (e) phase angle. See section 3.3.7 for a more detailed description of the BDRs.
The 8-color Map Projected Multispectral RDR (MDR) data set consists of a mosaicked global color map of 8-color image sets, as reflectance corrected to i = 30¼, e = 0¼, and g = 30¡ sampled at a scale of 64 pixels per degree, compiled from images taken as a part of the global 8-color map campaign described in section 2.3.1.3. Each of 54 map tiles, defined geographically in the same manner as the BDRs, is composed of 8 bands corresponding to 8 of the 11 WAC filters. Versions 0, 1, and 2 of the map also contain 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id for each image set, (b) MDR metric, a metric used to determine the stacking order of component images (see section 2.5.2.3), and (c) solar incidence angle, (d) emission angle, and (e) phase angle for the 750-nm image in the set. Versions 0, 1, and 2 are uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles (and different from parameters used in map products containing higher-incidence angle data).
Version 3 of the map, delivered one year after the end of orbital operations, is compiled differently. Instead of the value from any single image being used at a particular pixel location in a given wavelength band, the value used is the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. The 9 backplanes are redefined, and contain (a) the count of 8-color image sets at each location, and (b-j) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 3 is controlled using version 1 DDRs (where image control uses NAC and WAC G-filter images), and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. For the south polar region only, there is a redundant tile having lower spatial resolution that eliminates coverage gaps present in the nominal version of the tile.
Version 4, delivered two years after the end of orbital operations, is similar to version 3 except that its map projection uses version 2 DDRs (where image control is based on WAC G-filter images only), resulting in less blur during averaging of overlying images. The MDR version 4 dataset has 6 special case maps with different parameters and file naming than the other maps. In Mercury charts H01 and H03, there are additional higher resolution maps with "128PPD" in the file name which provide higher resolution for a limited area using only images with resolution better than 500 m/pixel. The H15 chart has an additional version (also present in version 3) with more complete polar coverage using lower resolution images to 2700 m/pixel, with "_2700_" in the file name.
See section 3.3.8 for a more detailed description of the MDRs.
The 3-color Map Projected Multispectral RDR (MD3) data set consists of a mosaicked global color map of 3-color image sets, as reflectance corrected to i = 30¼, e = 0¼, and g = 30¼ sampled at a scale of 128 pixels per degree, compiled from images taken as a part of the regional 3-color map campaign described in section 2.3.2.3. Each map tile, defined geographically in the same manner as for BDRs and MDRs, contains 3 bands corresponding to 3 of the 11 WAC filters. Version 0 of the map contains 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id for each image set, (b) the same metric as for MDRs, to determine the stacking order of component images (see section 2.5.2.3) except with the limiting spatial resolution modified, and (c) solar incidence angle, (d) emission angle, and (e) phase angle for the 750-nm image in the set. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles (and different from parameters used in map products containing higher-incidence angle data).
Version 1 of the map, delivered at one year after the end of orbital operations, is compiled differently. Instead of the value from any single image being used at a particular pixel location in a given wavelength band, the value used is the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. The 4 backplanes are redefined, and contain (a) the count of 3-color image sets at each location, and (b-d) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 1 is controlled using version 1 DDRs, and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2, delivered two years after the end of orbital operations, is similar to version 1 except that its map projection uses version 2 DDRs, resulting in less blur during averaging of overlying images. See section 3.3.9 for a more detailed description of the MD3s.
The 5-color Map Projected Multispectral RDR (MP5) data set consists of a mosaicked regional color map of 5-color image sets, as reflectance corrected to i = 30¼, e = 0¼, and g = 30¡ sampled at a scale of 128 pixels per degree, compiled from images taken as a part of the regional 5-color map campaign described in section 2.3.3.2. There is a single map tile, the north polar tile, that contains 5 bands corresponding to 5 of the 11 WAC filters. Version 1 of the map, delivered one year after the end of orbital operations, is compiled using at a particular pixel location in a given wavelength band, the average from all of the images at that location where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. Six backplanes contain (a) the count of 5-color image sets at each location, and (b-f) for each wavelength band of corrected reflectance, the standard deviation to the average value. In addition, version 1 is controlled using version 1 DDRs, and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2, delivered two years after the end of orbital operations, is similar to version 1 except that its map projection uses version 2 DDRs, resulting in less blur during averaging of overlying images. Additional images that were left out of the averaging in version 1 due to excessive misregistration blur are now included in version 2, filling in some gaps and increasing the available images for averaging. See section 3.3.10 for a more detailed description of the MP5s.
The Map Projected High-Incidence Angle Basemap Illuminated from the East RDR (HIE) data set consists of a global monochrome map of reflectance corrected to i = 30¼, e = 0¼, and g = 30¡ at a resolution of 256 pixels per degree, compiled from images taken as a part of the global high-incidence angle imaging campaign illuminated from the east, described in section 2.3.3.1. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Version 0 of the map also contains 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id, (b) the same metric as for BDRs, to determine the stacking order of component images (see section 2.5.2.3), modified for the optimal incidence angle to be 78¡ instead of 68¡ or 74¡, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (and different from parameters used in map products containing lower-incidence angle data). Version 1, released one year after the end of orbital operations, is compiled using NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 78¡ with illumination from the east. It is controlled and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2, released two years after the end of orbital operations, differs from version 1 in that the intended illumination geometry is low emission angle and incidence angle near 86¡ with illumination from the east. See section 3.3.11 for a more detailed description of the HIEs.
The Map Projected High-Incidence Angle Basemap Illuminated from the West RDR (HIW) data set consists of a global monochrome map of reflectance corrected to i = 30¼, e = 0¼, and g = 30¡ at a resolution of 256 pixels per degree, compiled from images taken as a part of the global high-incidence angle imaging campaign illuminated from the west, described in section 2.3.3.1. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Version 0 of the map also contains 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id, (b) the same metric as for BDRs, to determine the stacking order of component images (see section 2.5.2.3), modified for the optimal incidence angle to be 78¡ instead of 68¡ or 74¡, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to higher solar incidence angles (and different from parameters used in map products containing lower-incidence angle data). Version 1, released one year after the end of orbital operations, is compiled using NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 78¡ with illumination from the west. It is controlled and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2, released two years after the end of orbital operations, differs from version 1 in that the intended illumination geometry is low emission angle and incidence angle near 86¡ with illumination from the west. See section 3.3.12 for a more detailed description of the HIWs.
The Map Projected Low-Incidence Angle Basemap RDR (LOI) data set consists of a global monochrome map of reflectance corrected to i = 30¼, e = 0¼, and g = 30¡ at a resolution of 256 pixels per degree. Each map tile, defined geographically in the same manner as for BDRs, contains a single band that merges NAC and WAC 750-nm images. Each map also contains 5 additional bands representing ÒbackplaneÓ data as follows: (a) observation id, (b) the same metric as for MDRs, to determine the stacking order of component images (see section 2.5.2.3) except with the limiting spatial resolution modified to be the same as for BDRs, (c) solar incidence angle, (d) emission angle, and (e) phase angle. Version 1, released one year after the end of orbital operations, is compiled in part based on images taken as a part of the global low-incidence angle imaging campaign described in section 2.3.2.1, but it also includes any NAC or WAC 750-nm images from any campaign that best fit the intended illumination geometry, i.e., low emission angle and incidence angle near 45¡. It is controlled and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. Version 2, released two years after the end of orbital operations, fills a gap in coverage near the south pole with an image scaled in brightness to match the adjacent coverage. See section 3.3.13 for a more detailed description of the LOIs.
The Regional Targeted Mosaic RDR (RTM) data set consists of regional maps of reflectance corrected to i = 30¼, e = 0¼, g = 30¡ at resolutions optimized to each mosaic, compiled from images taken as a part of targeted NAC strips or targeted WAC color observations. All but two of the regional maps each include the data from a single targeted observation of one of four types: (a) a high-resolution NAC strip as described in section 2.3.1.5, (b) a 3-color WAC target as described in section 2.3.1.6, (c) an 8- or 11-color WAC photometry target as described in section 2.3.1.7, or (d) an 11-color WAC target as described in section 2.3.3.5. Each map is projected orthographically centered on the mid-point of the target, and contains 1, 3, 8, or 11 image bands depending on the type of observation (NAC or WAC 3-, 8-, or 11-color targeted observation). Each NAC mosaic also contains 4 additional bands representing "backplane" data as follows: (a) observation id, (b) solar incidence angle, (c) emission angle, and (d) phase angle. Each WAC color product contains 3 backplanes: (a) solar incidence angle, (b) emission angle, and (c) phase angle. If the observation is a WAC color observation, the additional bands are evaluated for the 750-nm filter. Version 0 is uncontrolled, projected onto an ellipsoidal model of Mercury, and photometrically corrected using a Hapke photometric model with parameters optimized to lower solar incidence angles for the WAC color mosaics and to higher solar incidence angles for the NAC mosaics. Version 1 is controlled and projected onto a global digital elevation model. It uses a KaasalainenÐShkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products.
The two specialized RTMs are regional WAC 3-color maps of Caloris and b30, high-quality regional color mosaics of these regions of high scientific interest. The images used to create the mosaics were purposely acquired with no compression during a time interval of just a few weeks, to minimize differences in the illumination conditions and calibration differences across the mosaic. From the overlap of images within these regional mosaics, a spatial correction for scattered light inherent in the instrument was developed for and applied to these image sets.
See section 3.3.14 for a more detailed description of the RTMs.
Data Product |
PDS Data Set ID |
Data Processing Level |
Example PDS Labels |
Experiment Data Record (EDR) |
MESS-E/V/H-MDIS-2-EDR-V1.0 |
2 |
See EDR SIS |
Calibrated Data Record (CDR) |
MESS-E/V/H-MDIS-4-CDR-CALDATA-V1.0 |
4 |
Section 3.3.5 Appendix C |
Derived Data Record (DDR) |
MESS-E/V/H-MDIS-6-DDR-GEOMDATA-V1.0 |
6 |
Section 3.3.6 Appendix D |
Map Projected Basemap RDR (BDR) |
MESS-H-MDIS-5-RDR-BDR-V1.0 |
5 |
Section 3.3.7 Appendix E |
8-Color Map Projected Multispectral RDR (MDR) |
MESS-H-MDIS-5-RDR-MDR-V1.0 |
5 |
Section 3.3.8 Appendix F |
3-Color Map Projected Multispectral RDR (MD3) |
MESS-H-MDIS-5-RDR-MD3-V1.0 |
5 |
Section 3.3.9 Appendix G |
5-Color Map Projected Multispectral RDR (MP5) |
MESS-H-MDIS-5-RDR-MP5-V1.0 |
5 |
Section 3.3.10 Appendix H |
Map Projected High-incidence Angle Basemap Illuminated from the East RDR (HIE) |
MESS-H-MDIS-5-RDR-HIE-V1.0 |
5 |
Section 3.3.11 Appendix I |
Map Projected High-incidence Angle Basemap Illuminated from the West RDR (HIW) |
MESS-H-MDIS-5-RDR-HIW-V1.0 |
5 |
Section 3.3.12 Appendix J |
Map Projected Low-incidence Angle Basemap RDR (LOI) |
MESS-H-MDIS-5-RDR-LOI-V1.0 |
5 |
Section 3.3.13 Appendix K |
Map Projected Regional Targeted Mosaic RDR (RTM) |
MESS-H-MDIS-5-RDR-RTM-V1.0 |
5 |
Section 3.3.14 Appendix L |
Table 2-14: Definitions of MDIS data products. EDRs are not described in this document.
Data from the MESSENGER WAC and NAC are archived together. The archive includes level 2 (and above) Committee on Data Management and Computation (CODMAC) data (Table 2-15), standard and special data products (as delineated in Applicable Document 4), and documentation describing the generation of the products. Each MDIS data product has a unique file name and follows a specified file naming convention (see section 3.3).
NASA |
CODMAC |
Description |
Packet data |
Raw - Level 1 |
Telemetry data stream as received at the ground station, with science and engineering data embedded. |
Level-0 |
Edited - Level 2 |
Instrument science data (e.g., raw voltages, counts) at full resolution, time ordered, with duplicates and transmission errors removed. |
Level 1-A |
Calibrated - Level 3 |
Level 0 data that have been located in space and may have been transformed (e.g., calibrated, rearranged) in a reversible manner and packaged with needed ancillary and auxiliary data (e.g., radiances with the calibration equations applied). |
Level 1-B |
Resampled - Level 4 |
Irreversibly transformed (e.g., resampled, remapped, calibrated) values of the instrument measurements (e.g., radiances, magnetic field strength). |
Level 1-C |
Derived - Level 5 |
Level 1A or 1B data that have been resampled and mapped onto uniform space-time grids. The data are calibrated (i.e., radiometrically corrected) and may have additional corrections applied (e.g., terrain correction). |
Level 2 |
Derived - Level 5 |
Geophysical parameters, generally derived from Level 1 data, and located in space and time commensurate with instrument location, pointing, and sampling. |
Level 3 |
Derived - Level 5 |
Geophysical parameters mapped onto uniform space-time grids. |
|
Ancillary Ð Level 6 |
Data needed to generate calibrated or resampled data sets. |
Table 2-15: Processing Levels for Science Data Sets.
MESSENGER WAC and NAC image CDRs and RDRs are produced by the MESSENGER Science Operations Center (SOC) operated jointly by APL and ACT. In some cases they are also generated by members of the MESSENGER science team. The CDRs are generated from EDRs through a data pipeline that corrects the EDRs for dark counts, flat field effects, non-linearity in response, wavelength-dependent responsivity, and time- and detector temperature-dependent variations in responsivity.
At the end of the evaluation and validation period, the data are organized and stored in the directory structure described in section 3.3, along with fiduciary checksums for transmittal to the PDS Imaging node. The transmittal process is described in section 2.5.3. These products are used for engineering support, direct science analysis, and construction of other science products.
Laboratory and in-flight measurements were used to derive values for the terms of the calibration equation (shown in Equation 1 below) for both the WAC and NAC. Details of how these measurements were made can be found in Hawkins et al. (2007) [Applicable Document 9]. Both instruments measure relative light intensity in engineering units referred to as data number [DN]. DNs are generally converted to radiance, L (W m-2-mm-1-sr-1), following the calibration equation:
[1]
where:
L(x,y,f,MET) is the calibrated radiance in column x, row y, through filter f measured at time MET
DN(x,y,f,T,t,b,MET) is the raw DN measured by the pixel in column x, row y, through filter f, at CCD temperature T and exposure time t, for binning mode b, and Mission Elapsed Time (MET),
Dk(x,y,T,t,b) is the dark level in a given pixel, derived either from the dark strip or estimated from exposure time and CCD temperature,
Sm(x,y,t,b) is the scene-dependent frame transfer smear for the pixel,
Flat(x,y,f,b) is the non-uniformity or Òflat-fieldÓ correction at this pixel location,
Resp(f,T,b) is temperature-dependent responsivity, relating dark-, flat-, and smear-corrected DN per unit exposure time to radiance,
t is the exposure time in milliseconds.
To convert from radiance to I/F (also known as radiance factor, the ratio of measured radiance to that which would be measured from a white perfectly Lambertian surface), which is used to populate CDRs, the following expression should be applied:
I_over_F(x,y,f,MET) = L(x,y,f,MET) / Correct(f,MET) * pi * (SOLAR_DISTANCE/149597870.691)^2 / F(f) [2]
where:
L(x,y,f,MET) is calibrated radiance calculated as described above for some filter f at some time MET
SOLAR_DISTANCE is that value for distance of the target object from the center of the Sun in kilometers (as indicated by the keyword SOLAR_DISTANCE),
149597870.691 is the number of kilometers in 1 AU, and
F(f) is effective average solar irradiance at 1 AU sampled under the filter bandpass (Table 2-16).
Correct(f,MET) is a time-dependent scalar correction applied to a whole image. For the NAC, Correct(f,MET) is unity and only one version of I/F is generated, with the character string "IF" in the file name. For the WAC, two versions of I/F are generated, with (IF) and without (IU) an empirical correction for responsivity that varies day by day. Derivation of values for Correct(f,MET) for the WAC are described by Denevi et al. (2016) [Applicable Document 14].
Two types of pixels in an EDR cannot be validly calibrated to either radiance or I/F:
á Pixels under the dark mask at the edge of the detector do not measure light from the scene, yet deviation of their calibrated value from zero is a valuable measure of calibration residuals. The average calibrated value under the dark mask is reported in the label as DARK_STRIP_MEAN, but the actual pixel values are replaced by the value indicated in the label for CORE_NULL.
á Saturated pixels do not have a known correspondence to scene radiance. The pixel values in saturated pixels are replaced by the value indicated in the label for CORE_HIGH_INSTR_SATURATION.
These keywords are discussed further in Appendix B.
Imager |
Filter Number |
Band Center, nm |
Bandwidth, nm |
Solar Irradiance, W m-2 µm-1 |
NAC |
N/A |
747.70 |
52.55 |
1278.85 |
WAC |
1 |
698.76 |
5.30 |
1429.10 |
2 |
701.27 |
196.51 |
1432.13 |
|
3 |
479.87 |
10.14 |
2091.95 |
|
4 |
558.91 |
5.82 |
1833.26 |
|
5 |
628.81 |
5.52 |
1669.08 |
|
6 |
433.21 |
18.11 |
1733.07 |
|
7 |
748.73 |
5.09 |
1293.93 |
|
8 |
947.03 |
6.15 |
813.27 |
|
9 |
996.23 |
14.30 |
741.46 |
|
10 |
898.80 |
5.08 |
900.80 |
|
11 |
1012.56 |
33.33 |
714.15 |
|
12 |
828.39 |
5.20 |
1062.92 |
Table 2-16: Solar irradiance used to convert radiance to units of I/F.
The sequence of processing that creates a version 0 DDR is as follows. Gimbal positions are extracted from the gimbal C kernel. Using that and other SPICE kernels, the equipotential surface intercept is calculated for each spatial pixel. The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel. For that latitude and longitude, solar incidence, emission, and phase angles are determined.
The generation of version 1 and 2 DDRs differs in two ways. Gimbal positions are extracted from smithed c-kernels, in which gimbal position has been adjusted to minimize misregistration of overlapping images. Using that and other SPICE kernels, the intercept on a global digital elevation model (DEM) is calculated for each spatial pixel.
The sequence of processing that creates a BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM from CDRs and DDRs (Figure 2-17) is as follows:
(a) EDRs are assembled from raw data.
(b) Radiance images are created from the EDRs and calibration files.
(c) Radiance is converted to I/F CDRs by dividing by (empiricalcorrection * pi * solar flux at 1 AU * heliocentricdistance^2).
(d) I/F is converted to reflectance through a photometric correction to i = 30¼, e = 0¼, g=30¡. Early versions of these products used a Hapke correction; the final versions used a KaasalainenÐShkuratov correction as described by Domingue et al. (2016) [Applicable Document 13].
(e) Gimbal positions are extracted from the spacecraft housekeeping and formatted as a gimbal C kernel.
(f) Using the gimbal C kernel and other SPICE kernels, DDRs are created. The surface intercept on Mercury's surface is calculated for each spatial pixel. The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel. For that latitude and longitude, solar incidence, emission, and phase angles are determined at an equipotential surface. For version 0 DDRs, latitude and longitude are calculated using the best-determined spacecraft and instrument pointing values, spacecraft position, and camera model recorded in SPICE kernels, and an ellipsoidal model of the planet surface. For version 1 and 2 DDRs, c-smithed kernels and a global digital elevation model (DEM) are used. The DEM was derived along with version 1 DDRs, using a least-squares bundle adjustment of common features measured as tie point coordinates in overlapping NAC and WAC-G filter images, as described by Becker et al. (2016) [Applicable Document 15].
(g) Reflectance corrected to i = 30¼, e = 0¼, g=30¡ from the WAC and/or NAC is map projected into multiband map products using the latitude and longitude information in the DDRs. The same procedure is used on DDRs to assemble the backplanes with derived information.
Prior to the final two deliveries of products at end of mission, all map products used data from simple mapping campaigns, and a stacking order to determine Òwhich image is on topÓ. For the deliveries at one and two years after the end of orbital operations, regional or global multispectral maps (MDRs/MD3s/MP5s and two RTMs covering the Caloris and b30 basins) employed an averaging procedure using all overlapping images at a given latitude and longitude where criteria for image scale, photometric geometry, and detector temperature are met. The averaging approach minimizes artifacts of time-variable instrument calibration. Also, those end-of-mission products mixed images from different campaigns to more closely approach desired lighting geometries or to fill gaps.
Separate stacking orders (Òwhich image is on topÓ) are defined separately for BDRs, HIEs/HIWs, and MDRs/MD3s/MP5s/LOIs. Which images were taken as part of the basemap or color mapping campaigns represented by these data products is indicated within an observation table used internally at the MESSENGER Science Operations Center. In the case of all maps, certain images are excluded for various reasons (limits on resolution, lighting, periods of time with noisy images, image motion smear) to improve the quality and uniformity of the products.
For BDRs, the objective is to have Òon topÓ those images with high spatial resolution, low emission angle, and as close as possible to a moderately high solar incidence angle. For version 0 BDRs that angle is 68¡, and for version 1 and 2 it is 74¡. These angles minimize shadows while accentuating topographic shading. Any image taken as part of the basemap campaign was a candidate to include in version 0 BDRs; any image taken as part of any campaign with suitable lighting was a candidate to include in version 1 and 2 BDRs. The stacking order is determined by evaluating at the camera boresight a metric that represents both spatial resolution and image geometry; lowest values for the metric represent the ÒbestÓ image. The ÒworstÓ complete, map-projected image with the highest value for the metric is laid into the BDR first; then the complete image with the second-highest value is laid in second, overwriting the first image where the coverage coincides, and so on until the complete ÒbestÓ image with the lowest value for the metric is on top.
For versions 0 and 1, where abs(lat) ² 65¡ and i ³ NN¡, the metric was:
PIXEL_SCALE / (cos e * ( cos ( flatten_factor * i) / cos ( flatten_factor * NN ) ) )
where i is solar incidence angle, e is emission angle, lat is planetocentric latitude, and flatten_factor is set to 0.85 to de-emphasize low solar incidence angles.
Where abs(lat) ² 65¡ and i < NN¡, the metric is:
PIXEL_SCALE / (cos e * (cos NN / cos i))
Where abs(lat) > 65¡, the metric is:
PIXEL_SCALE / (cos i * cos e )
For version 0, NN= 68¡ and for versions 1 and 2 NN=74¡.
For version 2 BDRs, where abs(lat)²80¡ and i³74¡, the metric is:
PIXEL_SCALE / (cos e * ( cos ( flatten_factor * i) / cos ( flatten_factor * 74¡) ) )
Where abs(lat) <= 80¡ and i < 74¡, the metric is:
PIXEL_SCALE / (cos e * (cos 74¡ / cos i))
Where abs(lat)>80¡, the metric is:
PIXEL_SCALE / (cos i * cos e )
In each case, values for PIXEL_SCALE less than 166 meters are reset to 166 meters.
The stacking order for HIEs and HIWs parallels that for BDRs, except that the "crossover" solar incidence angle (which tends to be "on top") is 86¡ instead of 74¡ and the emission angle is weighted differently.
Where i ³ 86¡, the metric is:
PIXEL_SCALE / (cos (1.5*e) * ( cos ( flatten_factor * i) / cos ( flatten_factor * 86¡ ) ) )
Where i < 86¡, the metric is:
PIXEL_SCALE / (cos (1.5*e) * (cos 86¡ / cos i))
For LOIs and early versions of MDRs and MD3s, the objective is to have Òon topÓ those images with high spatial resolution, low emission angle, and low solar incidence angle. The stacking order is determined in a fashion comparable to that used for BDRs, with some modifications. If the sequence includes multiple WAC filters, only a portion of each image is used, in which the same region of Mercury is observing in all filters of the color sequence. The image quality metric is evaluated at the camera boresight of the middle image in that sequence; lowest values represent the ÒbestÓ image. For each color sequence or image taken as part of the low-incidence campaign, the ÒworstÓ image or part of a sequence with overlapping coverage in all filters (highest value of the metric) is map-projected and laid into the data product first; then the image or overlap region with the second-highest value is laid in second, overwriting the first overlap region, and so on until the ÒbestÓ image or overlap region with the lowest metric is on top. At all latitude and solar incidence angles, the metric is:
PIXEL_SCALE / (cos i * cos e )
where for MDRs values for PIXEL_SCALE less than 665 meters are reset to 665 meters, for MD3s and MP5 values for PIXEL_SCALE less than 332 meters are reset to 332 meters, and for LOIs values for PIXEL_SCALE less than 166 meters are reset to 166 meters.
Figure 2-17: Sequential processing of EDRs to yield RDRs, showing roles of CDRs and DDRs. BDRs and MDRs are shown as examples but the same flow yields MD3s, MP5s, HIEs, HIWs, LOIs, or RTMs.
The MESSENGER Science Operations Center (SOC) operates under the auspices of the MESSENGER Project Scientist to plan data acquisition and generate and validate data archives. The SOC supports and works with the Mission Operations Center (MOC), the Science Team, instrument scientists, and the PDS.
The SOC is located at JHU/APL. The SOC produces early versions of products that can be used by the science and instrument teams. They are of the same type, content, and format as the final science products with default information for unknown data such as pointing and spacecraft housekeeping.
At the end of the evaluation and validation period, the data are organized and stored in the directory structure described in section 3.3, along with fiduciary checksums. This directory structure is compressed into a single Òzip archiveÓ file for transmittal to the PDS imaging node. The zip archive preserves the directory structure internally so that when it is decompressed the original directory structure is recreated at the PDS node. The zip archive is transmitted to the PDS node via FTP to a specified URL.
Several MDIS archive releases, as detailed in the MESSENGER Data Management and Archiving Plan [Applicable Document 4], are assembled and transmitted to PDS. At least two weeks before the deadline for transmittal, the zip archive file is transmitted to the PDS node. At the same time, a letter of transmittal is sent which provides a record of the fiduciary checksums provided in the archive file itself. Within several days of transmittal, the node acknowledges receipt (but not verification) of the archive and letter of transmittal. If acknowledgement is not received, or if problems are reported, the MESSENGER SOC immediately takes corrective action to affect successful transmittal.
After transmittal, the PDS node uncompresses the zip archive file and independently calculates the fiduciary checksums for each file. The calculated checksums are compared to the checksums in the transmittal letter and those recorded in the archive itself. The node then performs any additional verification and validation of the data provided and reports any discrepancies or problems to the MESSENGER SOC. Typically the node performs these checks and inspections in about two weeks. After inspection is completed to the satisfaction of the PDS node, the node issues to the MESSENGER SOC acknowledgement of successful receipt.
The MDIS data products comply with the PDS standards for file formats and labels, specifically the PDS image and table data objects [Applicable Documents 2 and 3]. Please see Appendix A for definitions of PDS data archive terms.
Two time standards are used in MDIS data products:
á spacecraft time in seconds (PDS label keywords SPACECRAFT_CLOCK_START_-COUNT and SPACECRAFT_CLOCK_STOP_COUNT)
á UTC (PDS label keywords START_TIME, STOP_TIME, and PRODUCT_CREA-TION_TIME)
The following bulleted list outlines the computational assumptions for the geometric and viewing data provided in the PDS label. There are two coordinate systems in use: 1) the celestial reference system used for target and spacecraft position and velocity vectors, and camera pointing; and 2) the planetary coordinate system for geometry vectors and target location. The celestial coordinate system is J2000 (Mean of Earth equator and equinox of J2000). The planetary coordinate system is planetocentric with respect to a reference ellipsoid. Through the final, end-of-mission products, the assumed ellipsoid is a sphere with 2440 km radius; in end-of-mission products, the sphere is 2439.4 km.
COMPUTATIONAL ASSUMPTIONS
á The mid-point time of an observation is used for the geometric element computations.
á Label parameters reflect observed, not true, geometry. Therefore, light-time and stellar aberration corrections are needed as appropriate.
á The inertial reference frame is J2000 (also called EME2000).
á Target body latitudes and longitudes are planetocentric. The initial agreed upon Mercury ellipsoid is a sphere with a 2440 km radius; the sphere used at end of mission is 2439.4 km in radius.
á The "sub-point" of a spacecraft on a target body is defined by the surface intercept of the spacecraft-to-target-body-center vector. This point is not necessarily the closest point on the target body to the spacecraft. This definition gives sub-point latitude and longitude that are independent of the targetÕs reference ellipsoid.
á Distances are in km, speeds in km/sec, angles in degrees.
á Angular rates in degrees/sec, unless otherwise noted.
á Angle ranges are 0 to 360 degrees for azimuths and local hour angle. Longitudes range from 0 to 360 degrees (positive to the East). Latitudes range from -90 to 90 degrees.
The data are organized following PDS standards and transferred to the PDS for distribution to the science community. Data will be stored under unique file names as defined in Section 3.3.
Data validation falls into two types, validation of the science data and validation of the compliance of the archive with PDS archiving and distribution requirements. The first type of validation is carried out by the Science Team, and the second is overseen by the PDS, in coordination with the Science Team.
The formal validation of data content, adequacy of documentation, and adherence to PDS archiving and distribution standards is subject to an external peer review. Peer reviews are scheduled and coordinated by the PDS. The peer review process may result in "liens," actions recommended by the reviewers or by PDS personnel to correct the archive. All liens must be resolved by the dataset provider: the SOC for Level 1 data, and the Science Team for higher-level data products, calibration data, and calibration algorithms. Once the liens are cleared, PDS does a final validation prior to packaging and delivery.
The SOC periodically reports results of validation to the MESSENGER Science Steering Committee. If the volumes are approved for release by the Project, then the SOC will transfer the archives to the PDS [Applicable Document 4].
Data that comprise the MESSENGER Image Archive are formatted according to the standards of the Planetary Data System, as documented in the PDS Standards Reference manual [Applicable Document 3]. Archive-quality data sets include everything needed to understand and utilize the data. The raw images by themselves are insufficient for the science community to realize the full scientific potential of the data. Thus, the MESSENGER project provides as part of the archive the ancillary data to perform radiometric, photometric, and cartographic processing. Additionally, a documentation set is provided to describe the data products, imaging instruments, and mission operations.
Geometric elements fully describe the viewing geometry of each observation. The geometric elements are organized according to the SPICE kernel concepts adopted by the Navigational Ancillary Information Facility (NAIF) at the Jet Propulsion Laboratory. SPICE is an acronym for Spacecraft, Planet, Instrument, C-matrix, and Event kernels (see http://naif.jpl.nasa.gov).
SPICE kernels evolve and improve as further analysis is done. The PDS data labels attached to the image data products are based on the most up-to-date SPICE information available at the time of product creation.
This section describes the contents of the MDIS Archive volumes, including the file names, file contents, file types, and organization responsible for providing the files. The indication that a file is required means that it is required by the PDS standards for archive volumes, as specified in the PDS Standards Reference, Applicable Document 3. See Appendix A for definitions of data archive terms.
There are ten separate CDR/RDR volumes, one for each of the ten CDR/RDR product types. The volumes bear the PDS-assigned volume IDs MSGRMDS_2001, MSGRMDS_3001, MSGRMDS_4001, MSGRMDS_5001, MSGRMDS_6001, MSGRMDS_7001, MSGRMDS_7101, MSGRMDS_7201, MSGRMDS_7301, and MSGRMDS_8001 for the CDRs, DDRs, BDRs, MDRs, MD3s, HIEs, HIWs, LOIs, MP5s, and RTMs respectively. An MDIS archive volume will contain the following directories below the root. The first five are always present, if applicable (the CALIB directory is only relevant to the EDR, CDR, MDR, MD3, MP5, and RTM volumes). BROWSE and EXTRAS are populated on a best-effort basis.
á INDEX
á CATALOG
á DOCUMENT
á DATA (named CDR, DDR, BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM based on product type)
á CALIB
á BROWSE
á EXTRAS
Files in the Root Directory (Table 3-1) include an overview of the archive, a description of the volume for the PDS Catalog, and a list of errata or comments about the archive. The following files are contained in the Root Directory.
File Name |
Required? |
File Contents |
AAREADME.TXT |
Yes |
General information file. Provides users with an overview of the contents and organization of the associated volume, general instructions for its use, and contact information. |
ERRATA.TXT |
No |
Text file for identifying and describing errors and/or anomalies found in the current volume, and possibly previous volumes of a set. Any known errors for the associated volume will be documented in this file. |
VOLDESC.CAT |
Yes |
PDS file containing the VOLUME object. This gives a high-level description of the contents of the volume. Information includes: production date, producer name and institution, volume ID, etc. |
Table 3-1: Root Directory Contents.
Files in the Index Directory (Table 3-2) are provided to help the user locate products on the archive volume. The following files are contained in the Index Directory.
File Name |
Required? |
File Contents |
INDXINFO.TXT |
Yes |
Identifies and describes the function of each file in the index subdirectory. This includes a description of the structure and contents of the index table and usage notes. |
INDEX.TAB |
Yes |
The image index file is organized as a table: there is a row for each image on the volume; the columns contain parameters that describe the observation and camera states of the images. Information includes viewing geometry (such as latitude and longitude of the image center, sun and observation angles) and camera state information such as filter wheel position, spacecraft clock count, time of observation, image integration time, and camera modes. |
INDEX.LBL |
Yes |
Detached PDS label for INDEX.TAB that describes its organization and contents. |
MD5.TAB |
No |
The checksum table is a listing of all files in the archive (with the exception of the checksum table itself) that gives the MD5 checksum (message digest) for the file and the full path including file name. It is generated by the commonly available "MD5Deep" utility. This file is useful as a manifest for the archive and for data integrity assurance. |
MD5.LBL |
No |
Detached PDS label for MD5.TAB. |
Table 3-2: Index Directory Contents.
Tables 3-3 and 3-4 list the columns in the CDR/DDR and BDR/MDR/MD3/MP5/HIE/HIW/ LOI/RTM index files, respectively. They are the most significant keywords pulled from labels of the various products. The lists are comprehensive in the sense that they include the important keywords for all data products. For any given data product, some of the fields are inapplicable and are set to N/A.
Column |
Format |
CDR Example |
VOLUME_ID |
CHARACTER |
MSGRMDS_2001 |
PATH_NAME |
CHARACTER |
ÒCDR/2007_156Ó |
FILE_NAME |
CHARACTER |
ÒCW089570568G_RA_0.IMGÓ |
PRODUCT_ID |
CHARACTER |
ÒCW0089570568G_RA_0Ó |
OBSERVATION_ID |
CHARACTER |
Ò6747Ó |
DATA_QUALITY_ID |
CHARACTER |
Ò0000001000000000Ó |
MISSION_PHASE_NAME |
CHARACTER |
"VENUS 2 FLYBY" |
TARGET_NAME |
CHARACTER |
VENUS |
SEQUENCE_NAME |
CHARACTER |
Ò07156_APP_WAC_MOSAIC_1Ó |
PRODUCT_CREATION_TIME |
TIME |
2007-11-13T23:30:37 |
START_TIME |
TIME |
2007-06-05T22:40:41.702888 |
STOP_TIME |
TIME |
2007-06-05T22:40:41.768887 |
SPACECRAFT_CLOCK_START_COUNT |
CHARACTER |
Ò1/0089570568:950000Ó |
SPACECRAFT_CLOCK_STOP_COUNT |
CHARACTER |
Ò1/0089570568:990000Ó |
INSTRUMENT_ID |
CHARACTER |
"MDIS-WAC" |
FILTER_NUMBER |
ASCII_INTEGER |
7 |
CENTER_FILTER_WAVELENGTH |
ASCII_INTEGER |
750 <NM> |
EXPOSURE_DURATION |
ASCII_INTEGER |
66 <MS> |
EXPOSURE_TYPE |
CHARACTER |
AUTO |
DETECTOR_TEMPERATURE |
ASCII_REAL |
-39.86 <degC> |
FOCAL_PLANE_TEMPERATURE |
ASCII_REAL |
-20.19 <degC> |
FILTER_TEMPERATURE |
ASCII_REAL |
-20.66 <degC> |
OPTICS_TEMPERATURE |
ASCII_REAL |
-20.85 <degC> |
MESS:PIV_POS |
ASCII_INTEGER |
9007 |
MESS:PIV_POS_MOTOR |
ASCII_INTEGER |
1000 |
MESS:PIV_READ |
ASCII_INTEGER |
9007 |
MESS:FPU_BIN |
ASCII_INTEGER |
0 |
MESS:COMP12_8 |
ASCII_INTEGER |
0 |
MESS:COMP_ALG |
ASCII_INTEGER |
2 |
MESS:COMP_FST |
ASCII_INTEGER |
1 |
MESS:WVLRATIO |
ASCII_INTEGER |
4 |
MESS:PIXELBIN |
ASCII_INTEGER |
0 |
MESS:SUBFRAME |
ASCII_INTEGER |
0 |
RETICLE_POINT_RA_1 |
ASCII_REAL |
182.77358 <DEG> |
RETICLE_POINT_RA_2 |
ASCII_REAL |
172.41885 <DEG> |
RETICLE_POINT_RA_3 |
ASCII_REAL |
181.37369 <DEG> |
RETICLE_POINT_RA_4 |
ASCII_REAL |
170.89950 <DEG> |
RETICLE_POINT_DECLINATION_1 |
ASCII_REAL |
0.76231 <DEG> |
RETICLE_POINT_DECLINATION_2 |
ASCII_REAL |
2.21637 <DEG> |
RETICLE_POINT_DECLINATION_3 |
ASCII_REAL |
-9.59692 <DEG> |
RETICLE_POINT_DECLINATION_4 |
ASCII_REAL |
-8.12579 <DEG> |
SPACECRAFT_SOLAR_DISTANCE |
ASCII_REAL |
108040911.97274 <KM> |
SLANT_DISTANCE |
ASCII_REAL |
14090.89871 <KM> |
CENTER_LATITUDE |
ASCII_REAL |
35.73941 <DEG> |
CENTER_LONGITUDE |
ASCII_REAL |
226.54464 <DEG> |
HORIZONTAL_PIXEL_SCALE |
ASCII_REAL |
2530.43332 <M> |
SMEAR_MAGNITUDE |
ASCII_REAL |
10.38328 <PIXELS> |
RETICLE_POINT_LATITUDE_1 |
ASCII_REAL |
ÒN/AÓ |
RETICLE_POINT_LATITUDE_2 |
ASCII_REAL |
47.22207 <DEG> |
RETICLE_POINT_LATITUDE_3 |
ASCII_REAL |
24.61941 <DEG> |
RETICLE_POINT_LATITUDE_4 |
ASCII_REAL |
20.95210 <DEG> |
RETICLE_POINT_LONGITUDE_1 |
ASCII_REAL |
ÒN/AÓ |
RETICLE_POINT_LONGITUDE_2 |
ASCII_REAL |
244.79392 <DEG> |
RETICLE_POINT_LONGITUDE_3 |
ASCII_REAL |
208.68936 <DEG> |
RETICLE_POINT_LONGITUDE_4 |
ASCII_REAL |
239.57209 <DEG> |
SOLAR_DISTANCE |
ASCII_REAL |
108040911.97274 <KM> |
SUB_SOLAR_AZIMUTH |
ASCII_REAL |
11.49500 <DEG> |
SUB_SPACECRAFT_LATITUDE |
ASCII_REAL |
14.91164 <DEG> |
SUB_SPACECRAFT_LONGITUDE |
ASCII_REAL |
246.92915 <DEG> |
SPACECRAFT_ALTITUDE |
ASCII_REAL |
13114.84420 <KM> |
SUB_SOLAR_LATITUDE |
ASCII_REAL |
-1.29302 <DEG> |
SUB_SOLAR_LONGITUDE |
ASCII_REAL |
283.86863 <DEG> |
INCIDENCE_ANGLE |
ASCII_REAL |
64.85698 <DEG> |
PHASE_ANGLE |
ASCII_REAL |
30.69683 <DEG> |
EMISSION_ANGLE |
ASCII_REAL |
39.19187 <DEG> |
DARK_STRIP_MEAN |
ASCII_REAL |
7.81804628787e-05 |
MINIMUM |
ASCII_REAL |
7.81804628787e-05 |
MAXIMUM |
ASCII_REAL |
0.1620197892189 |
MEAN |
ASCII_REAL |
0.032525319648508 |
STANDARD_DEVIATION |
ASCII_REAL |
0.029913486227533 |
SATURATED_PIXEL_COUNT |
ASCII_REAL |
0 |
Table 3-3: CDR/DDR Index Table Contents.
Column |
Format |
BDR Example |
VOLUME_ID |
CHARACTER |
MSGRMDS_4001 |
PATH_NAME |
CHARACTER |
BDR/H03/ |
FILE_ NAME |
CHARACTER |
ÒMDIS_BDR_200PPD_H03NE.IMGÓ |
PRODUCT_ID |
CHARACTER |
ÒMDIS_BDR_200PPD_H03NEÓ |
SITE_NAME (RTM only) |
CHARACTER |
"Degas_South_Ray_NAC_Strip_2" |
PRODUCT_CREATION_TIME |
TIME |
2011-10-25T23:17:20.029 |
START_TIME |
TIME |
9999-01-01T01:01:01 |
STOP_TIME |
TIME |
9999-01-01T01:01:01 |
PRODUCT_VERSION_ID |
ASCII_INTEGER |
1 |
LINES |
ASCII_INTEGER |
6400 |
LINE_SAMPLES |
ASCII_INTEGER |
9216 |
BANDS |
ASCII_INTEGER |
2 |
MAP_PROJECTION_TYPE |
CHARACTER |
"EQUIRECTANGULAR" |
CENTER_LATITUDE |
ASCII_REAL |
0.0000000 <DEGREE> |
CENTER_LONGITUDE |
ASCII_REAL |
0.000000 <DEGREE> |
MAP_SCALE |
ASCII_REAL |
212.930169 <M/PIXEL> |
MAP_RESOLUTION |
ASCII_INTEGER |
200 <PIXEL/DEGREE> |
LINE_PROJECTION_OFFSET |
ASCII_REAL |
13000.000003 |
SAMPLE_PROJECTION_OFFSET |
ASCII_REAL |
3250.637830 |
MAXIMUM_LATITUDE |
ASCII_REAL |
25.0000000 <DEGREE> |
MINIMUM_LATITUDE |
ASCII_REAL |
0.0000000 <DEGREE> |
WESTERNMOST_LONGITUDE |
ASCII_REAL |
0.0000000 <DEGREE> |
EASTERNMOST_LONGITUDE |
ASCII_REAL |
36.0000000 <DEGREE> |
Table 3-4: BDR/MDR/MD3/MP5/HIE/HIW/LOI/RTM Index Table Contents.
The
files in the Catalog Directory (Table 3-5) provide a top-level understanding of
the mission, spacecraft, instruments, and data set. The files in this
directory become part of the PDS Catalog to provide background information for
the user searching for data. Their format and contents are further
specified in the PDS Standards Reference (Applicable Document 3). The
following files are found in the Catalog Directory.
File Name |
Required? |
File Contents |
CATINFO.TXT |
Yes |
Identifies and describes the function of each file in the catalog directory. |
MDIS_NNN_DS.CAT |
Yes |
Data set description, where NNN is replaced by CDR, DDR, BDR, MDR, MD3, MP5, HIE, HIW, LOI, or RTM. |
INSTHOST.CAT |
Yes |
Description of the MESSENGER spacecraft for the PDS catalog. |
MDIS_NAC_INST.CAT |
Yes |
Description of the MDIS NAC and WAC. |
NNN_MAP.CAT |
Yes |
MDIS data set map projection information, where NNN is replaced by BDR, MDR, MD3, HIE, HIW, LOI, or RTM (not applicable to CDR, DDR, or MP5). |
NNN_POLAR_MAP.CAT |
Yes |
MDIS data set map projection information for polar regions, where NNN is replaced by BDR, MDR, MD3, MP5, HIE, HIW, or LOI (not applicable to CDR, DDR, or RTM). |
MISSION.CAT |
Yes |
Description of the MESSENGER mission. |
PERSON.CAT |
Yes |
List of personnel associated with the MESSENGER PDS delivery. |
TARGET.CAT |
Yes |
List of astronomical and planetary targets in the images. |
REF.CAT |
Yes |
Catalog objectsÕ citation list for the PDS catalog. |
Table 3-5: Catalog Directory Contents.
The
Document Directory (Table 3-6) contains documentation to help the user
understand and use the archive data. The following files are contained in
the Document Directory.
File Name |
Required? |
File Contents |
DOCINFO.TXT |
Yes |
Identifies and describes the function of each file in the document directory. |
MDIS_CDR_RDRSIS.DOC |
Yes |
Software Interface Specification for the CDR/RDR data products as a Microsoft Word document. |
MDIS_CDR_RDRSIS.PDF |
Yes |
Software Interface Specification for the CDR/RDR data products as an Adobe PDF document. |
MDIS_CDR_RDRSIS.HTM |
Yes |
Software Interface Specification for the CDR/RDR data products as an HTML document. |
MDIS_CDR_RDRSIS.LBL |
Yes |
PDS label for MDIS_CDR_RDRSIS.DOC, MDIS_CDR_RDRSIS.PDF and MDIS_CDR_RDRSIS.HTM. |
PDSDD.FUL |
No |
PDS data dictionary. Includes definitions of all keywords used in MESSENGER data labels. |
Table 3-6: Document Directory Contents.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS CDR products have an Ò18.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Format: "pcrnnnnnnnnnf_tt_v"
p = product type = C calibrated
c = camera (W WAC or N NAC)
r = spacecraft-clock-partition-number minus 1 [0, 1] for pre- or post-spacecraft-clock-reset
nnnnnnnnn = Mission Elapsed Time (MET) counter taken from the image header (and same as original compressed filename from SSR). NOTE: this is a spacecraft clock seconds counter, and the value in the filename corresponds to the LAST second of the exposure.
f = Filter wheel position (A, B, C, D, E, F, G, H, I, J, K, L, U) for the WAC (see Table 3-7 below). It is M for the NAC, which has no filter wheel. It will be U if the position is unknown.
tt = data type (RA radiance, IF I/F, or IU I/F in the WAC if uncorrected empirically for time-variations in responsivity)
v = version number
The following is an example file name with a description of the individual components:
Filter Number |
Filter Filename Letter |
Wavelength (Flight) (nm) |
Width (Flight) (nm) |
1 |
A |
698.8 |
5.3 |
2 |
B |
700 |
600.0 |
3 |
C |
479.9 |
10.1 |
4 |
D |
558.9 |
5.8 |
5 |
E |
628.8 |
5.5 |
6 |
F |
433.2 |
18.1 |
7 |
G |
748.7 |
5.1 |
8 |
H |
947.0 |
6.2 |
9 |
I |
996.2 |
14.3 |
10 |
J |
898.8 |
5.1 |
11 |
K |
1012.6 |
33.3 |
12 |
L |
828.4 |
5.2 |
Table 3-7: Filter numbers and their bandpasses.
CW0014032676F_RA_0.IMG
For this image:
á Product type = CDR (C)
á Camera = WAC (W)
á Clock partition = 1 (pre-clock reset)
á MET = 014032676
á WAC filter wheel position = 6 (433nm/18 nm FWHM) (F)
á Data type = radiance (RA)
á Version number = 0
A Calibrated Data Record (CDR) is a single image that has been corrected for geometric and optical effects. The MDIS CDR data set consists of files that parallel Experiment Data Records (EDRs) in their format and directory structure. Each attached label points to a single-frame calibrated image in units of radiance or I/F as 32-bit PC_REAL or IEEE_REAL.
x, y dimensions = 1024/(MESS:FPU_BIN * MESS:PIXELBIN)
See section 2.5.2.1 for a description of how the CDR products are generated.
The label area of the data file conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the measurement data and provide engineering and observation parameters. A sample CDR label can be found in Appendix C. Table 3-8 below lists MDIS-specific values for CDR label keywords. See Appendix B for keyword descriptions.
As a result of an August 2009 flight software update, all MDIS CDRs were regenerated and redelivered to PDS with Release 5 (March 15, 2010). The keywords OBSERVATION_ID, MESS:IMG_ID_LSB, MESS:IMG_ID_MSB, and MESS:PIV_POS_MOTOR were added to the CDR labels with this update. CDRs from Mercury Flyby 2 and earlier have values of ÒN/AÓ for these keywords. The keyword MESS:PIV_GOAL is set to ÒN/AÓ after Mercury Flyby 2.
Keyword |
Valid Values |
|
INSTRUMENT_NAME |
ÒMERCURY DUAL IMAGING SYSTEM WIDE ANGLE CAMERAÓ ÒMERCURY DUAL IMAGING SYSTEM NARROW ANGLE CAMERAÓ |
|
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
|
OBSERVATION_TYPE |
"Albedo" |
"Monochrome,Oblique" |
"Albedo,Albedo Stereo" |
"Monochrome,Ridealong NAC" |
|
"Co-align Calibration" |
"Monochrome,Stereo" |
|
"Color" |
"Monochrome,Targeted" |
|
"Color,Emission Phase Function" |
"N/A" |
|
"Color,Southern Polar" |
"NAC WAC Calibration" |
|
"Color,Targeted" |
"Northern Polar" |
|
"Color,Targeted,Photometry" |
"Pivot Calibration" |
|
"Comet" |
"Satellite Search" |
|
"Dark Current" |
"Southern Polar" |
|
"Dark Polar Craters" |
"Southern Polar,Eleven Color" |
|
"Eleven Color,NAC WAC Calibration" |
"Stereo,Targeted" |
|
"Engineering" |
"Targeted,Eleven Color" |
|
"High Incidence" |
"Targeted,Photometry,Eleven Color" |
|
"Limb" |
"Thermal Calibration" |
|
"Min Phase Five Color" |
"Three Color" |
|
"Monochrome" |
"Vulcanoid Search" |
|
FILTER_NAME |
"430 BP 40", "430 BW 40" "480 BP 10", "480 BW 10" "560 BP 5", "560 BW 5" "630 BP 5", "630 BW 5" "700 BP 5", "700 BW 5" "750 BP 5", "750 BW 5" "830 BP 5", "830 BW 5" "900 BP 5", "900 BW 5" "950 BP 7", "950 BW 7" "1000 BP 15", "1000 BW 15" "1020 BP 40", "1020 BW 40" ÒN/AÓ |
|
FILTER_NUMBER |
Integer 1 - 12 ÒN/AÓ |
|
MESS:EC_FACTOR |
Empirical correction factor, Correct(f,MET) from the calibration equation in section 2.5.2.1.2. "N/A" for NAC, real number or "N/A" for WAC |
|
MESS:MET_EXP |
Time in seconds |
|
MESS:IMG_ID_LSB |
Integer 0 to 65535 |
|
MESS:IMG_ID_MSB |
Integer 0 to 255 |
|
MESS:ATT_CLOCK_COUNT |
Time in seconds |
|
MESS:ATT_Q1 |
-1.0 to 1.0 |
|
MESS:ATT_Q2 |
-1.0 to 1.0 |
|
MESS:ATT_Q3 |
-1.0 to 1.0 |
|
MESS:ATT_Q4 |
-1.0 to 1.0 |
|
MESS:ATT_FLAG |
Integer 0 to 7 |
|
MESS:PIV_POS_MOTOR |
Integer 0 to 65535 |
|
MESS:PIV_GOAL |
Integer -32768 to 32768 |
|
MESS:PIV_POS |
Integer -32768 to 32768 |
|
MESS:PIV_READ |
Integer 0 to 65535 |
|
MESS:PIV_CAL |
Integer -32768 to 32768 |
|
MESS:FW_GOAL |
Integer 0 to 65535 |
|
MESS:FW_POS |
Integer 0 to 65535 |
|
MESS:FW_READ |
Integer 0 to 65535 |
|
MESS:CCD_TEMP |
Integer 0 to 4095 |
|
MESS:CAM_T1 |
Integer 0 to 1023 |
|
MESS:CAM_T2 |
Integer 0 to 1023 |
|
MESS:EXPOSURE |
Time in seconds |
|
MESS:DPU_ID |
Integer 0 or 1 |
|
MESS:IMAGER |
Integer 0 or 1 |
|
MESS:SOURCE |
Integer 0, 1, or 2 |
|
MESS:FPU_BIN |
Integer 0 or 1 |
|
MESS:COMP12_8 |
Integer 0 or 1 |
|
MESS:COMP_ALG |
Integer 0 to 7 |
|
MESS:COMP_FST |
Integer 0 or 1 |
|
MESS:TIME_PLS |
Integer 0 to 3 |
|
MESS:LATCH_UP |
Integer 0 or 1 |
|
MESS:EXP_MODE |
Integer 0 or 1 |
|
MESS:PIV_STAT |
Integer 0 to 3 |
|
MESS:PIV_MPEN |
Integer 0 or 1 |
|
MESS:PIV_PV |
Integer 0 or 1 |
|
MESS:PIV_RV |
Integer 0 or 1 |
|
MESS:FW_PV |
Integer 0 or 1 |
|
MESS:FW_RV |
Integer 0 or 1 |
|
MESS:AEX_STAT |
Integer 0 to 4095 |
|
MESS:AEX_STHR |
Integer 0 to 65535 |
|
MESS:AEX_TGTB |
Integer 0 to 4095 |
|
MESS:AEX_BACB |
Integer 0 to 4095 |
|
MESS:AEX_MAXE |
Integer 0 to 989 |
|
MESS:AEX_MINE |
Integer 0 to 989 |
|
MESS:DLNKPRIO |
Integer 0 to 9 |
|
MESS:WVLRATIO |
Integer 0 to 32 |
|
MESS:PIXELBIN |
Integer 0, 2, 4, or 8 |
|
MESS:SUBFRAME |
Integer 0 to 5 |
|
MESS:SUBF_X1 |
Integer 0 to 1023 |
|
MESS:SUBF_Y1 |
Integer 0 to 1023 |
|
MESS:SUBF_DX1 |
Integer 0 to 1024 |
|
MESS:SUBF_DY1 |
Integer 0 to 1024 |
|
MESS:SUBF_X2 |
Integer 0 to 1023 |
|
MESS:SUBF_Y2 |
Integer 0 to 1023 |
|
MESS:SUBF_DX2 |
Integer 0 to 1024 |
|
MESS:SUBF_DY2 |
Integer 0 to 1024 |
|
MESS:SUBF_X3 |
Integer 0 to 1023 |
|
MESS:SUBF_Y3 |
Integer 0 to 1023 |
|
MESS:SUBF_DX3 |
Integer 0 to 1024 |
|
MESS:SUBF_DY3 |
Integer 0 to 1024 |
|
MESS:SUBF_X4 |
Integer 0 to 1023 |
|
MESS:SUBF_Y4 |
Integer 0 to 1023 |
|
MESS:SUBF_DX4 |
Integer 0 to 1024 |
|
MESS:SUBF_DY4 |
Integer 0 to 1024 |
|
MESS:SUBF_X5 |
Integer 0 to 1023 |
|
MESS:SUBF_Y5 |
Integer 0 to 1023 |
|
MESS:SUBF_DX5 |
Integer 0 to 1024 |
|
MESS:SUBF_DY5 |
Integer 0 to 1024 |
|
MESS:CRITOPNV |
Integer 0 or 1 |
|
MESS:JAILBARS |
Integer 0 or 1 |
|
MESS:JB_X0 |
Integer 0 to 1023 |
|
MESS:JB_X1 |
Integer 0 to 1023 |
|
MESS:JB_SPACE |
Integer 0 to 1023 |
Table 3-8. MDIS-specific values for CDR label keywords.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS DDR products have a Ò18.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Format: "pcrnnnnnnnnnf_tt_v"
p = product type = D derived
c = camera (W WAC or N NAC)
r = spacecraft-clock-partition-number minus 1 [0, 1] for pre- or post-spacecraft-clock-reset nnnnnnnnn = Mission Elapsed Time (MET) counter taken from the image header (and same as original compressed filename from SSR). NOTE: this a spacecraft clock seconds counter, and the value in the filename corresponds to the LAST second of the exposure.
f = Filter wheel position (A, B, C, D, E, F, G, H, I, J, K, L, U) for the WAC (see Table 3-7 above). It is M for the NAC, which has no filter wheel. It will be U if the position is unknown.
tt = data type (RA radiance, IF I/F, or DE derived products)
v = version number
The following is an example file name with a description of the individual components:
DW0089570568F_DE_0.IMG
For this image:
á Product type = DDR (D)
á Camera = WAC (W)
á Clock partition = 1 (pre-clock reset)
á MET = 089570568
á WAC filter wheel position = 6 (419nm/44 nm FWHM) (F)
á Data type = derived (DE)
á Version number = 0
The Derived Data Record (DDR) data set consists of files that parallel CDRs in their directory structure. Each DDR has 5 layers of data containing geometric information (latitude, longitude, incidence angle, emission angle, phase angle). This information is derived from pixel spatial coordinates and associated SPICE files. A DDR label is attached and points to a single multiband image in the DDR.
x, y dimensions = 1024/(MESS:FPU_BIN * MESS:PIXELBIN)
See section 2.5.2.2 for a description of how the DDR products are generated.
The label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the measurement data and provide engineering and observation parameters. A sample DDR label can be found in Appendix D. Table 3-9 below lists MDIS-specific values for DDR label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
||
INSTRUMENT_NAME |
ÒMERCURY DUAL IMAGING SYSTEM WIDE ANGLE CAMERAÓ ÒMERCURY DUAL IMAGING SYSTEM NARROW ANGLE CAMERA |
||
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
||
FILTER_NAME |
"430 BP 40", "430 BW 40" "480 BP 10", "480 BW 10" "560 BP 5", "560 BW 5" "630 BP 5", "630 BW 5" "700 BP 5", "700 BW 5" "750 BP 5", "750 BW 5" "830 BP 5", "830 BW 5" "900 BP 5", "900 BW 5" "950 BP 7", "950 BW 7" "1000 BP 15", "1000 BW 15" "1020 BP 40", "1020 BW 40" ÒN/AÓ |
||
OBSERVATION_TYPE |
"Albedo" |
"Monochrome,Oblique" |
|
"Albedo,Albedo Stereo" |
"Monochrome,Ridealong NAC" |
||
"Color" |
"Monochrome,Stereo" |
||
"Color,Emission Phase Function" |
"Monochrome,Targeted" |
||
"Color,Southern Polar" |
"NAC WAC Calibration" |
||
"Color,Targeted" |
"Northern Polar" |
||
"Color,Targeted,Photometry" |
"Southern Polar" |
||
"Dark Polar Craters" |
"Southern Polar,Eleven Color" |
||
"Eleven Color,NAC WAC Calibration" |
"Stereo,Targeted" |
||
"High Incidence" |
"Targeted,Eleven Color" |
||
"Limb" |
"Targeted,Photometry,Eleven Color" |
||
"Min Phase Five Color" |
"Three Color" |
||
"Monochrome" |
|
||
FILTER_NUMBER |
Integers 1 - 12 ÒN/AÓ |
||
MESS:MET_EXP |
Time in seconds |
||
MESS:IMG_ID_LSB |
Integer 0 to 65535 |
||
MESS:IMG_ID_MSB |
Integer 0 to 255 |
||
MESS:ATT_CLOCK_COUNT |
Time in seconds |
||
MESS:ATT_Q1 |
-1.0 to 1.0 |
||
MESS:ATT_Q2 |
-1.0 to 1.0 |
||
MESS:ATT_Q3 |
-1.0 to 1.0 |
||
MESS:ATT_Q4 |
-1.0 to 1.0 |
||
MESS:ATT_FLAG |
Integer 0 to 7 |
||
MESS:PIV_POS_MOTOR |
Integer 0 to 65535 |
||
MESS:PIV_GOAL |
Integer -32768 to 32768 |
||
MESS:PIV_POS |
Integer -32768 to 32768 |
||
MESS:PIV_READ |
Integer 0 to 65535 |
||
MESS:PIV_CAL |
Integer -32768 to 32768 |
||
MESS:FW_GOAL |
Integer 0 to 65535 |
||
MESS:FW_POS |
Integer 0 to 65535 |
||
MESS:FW_READ |
Integer 0 to 65535 |
||
MESS:CCD_TEMP |
Integer 0 to 4095 |
||
MESS:CAM_T1 |
Integer 0 to 1023 |
||
MESS:CAM_T2 |
Integer 0 to 1023 |
||
MESS:EXPOSURE |
Time in seconds |
||
MESS:DPU_ID |
Integer 0 or 1 |
||
MESS:IMAGER |
Integer 0 or 1 |
||
MESS:SOURCE |
Integer 0, 1, or 2 |
||
MESS:FPU_BIN |
Integer 0 or 1 |
||
MESS:COMP12_8 |
Integer 0 or 1 |
||
MESS:COMP_ALG |
Integer 0 to 7 |
||
MESS:COMP_FST |
Integer 0 or 1 |
||
MESS:TIME_PLS |
Integer 0 to 3 |
||
MESS:LATCH_UP |
Integer 0 or 1 |
||
MESS:EXP_MODE |
Integer 0 or 1 |
||
MESS:PIV_STAT |
Integer 0 to 3 |
||
MESS:PIV_MPEN |
Integer 0 or 1 |
||
MESS:PIV_PV |
Integer 0 or 1 |
||
MESS:PIV_RV |
Integer 0 or 1 |
||
MESS:FW_PV |
Integer 0 or 1 |
||
MESS:FW_RV |
Integer 0 or 1 |
||
MESS:AEX_STAT |
Integer 0 to 4095 |
||
MESS:AEX_STHR |
Integer 0 to 65535 |
||
MESS:AEX_TGTB |
Integer 0 to 4095 |
||
MESS:AEX_BACB |
Integer 0 to 4095 |
||
MESS:AEX_MAXE |
Integer 0 to 989 |
||
MESS:AEX_MINE |
Integer 0 to 989 |
||
MESS:DLNKPRIO |
Integer 0 to 9 |
||
MESS:WVLRATIO |
Integer 0 to 32 |
||
MESS:PIXELBIN |
Integer 0, 2, 4, or 8 |
||
MESS:SUBFRAME |
Integer 0 to 5 |
||
MESS:SUBF_X1 |
Integer 0 to 1023 |
||
MESS:SUBF_Y1 |
Integer 0 to 1023 |
||
MESS:SUBF_DX1 |
Integer 0 to 1024 |
||
MESS:SUBF_DY1 |
Integer 0 to 1024 |
||
MESS:SUBF_X2 |
Integer 0 to 1023 |
||
MESS:SUBF_Y2 |
Integer 0 to 1023 |
||
MESS:SUBF_DX2 |
Integer 0 to 1024 |
||
MESS:SUBF_DY2 |
Integer 0 to 1024 |
||
MESS:SUBF_X3 |
Integer 0 to 1023 |
||
MESS:SUBF_Y3 |
Integer 0 to 1023 |
||
MESS:SUBF_DX3 |
Integer 0 to 1024 |
||
MESS:SUBF_DY3 |
Integer 0 to 1024 |
||
MESS:SUBF_X4 |
Integer 0 to 1023 |
||
MESS:SUBF_Y4 |
Integer 0 to 1023 |
||
MESS:SUBF_DX4 |
Integer 0 to 1024 |
||
MESS:SUBF_DY4 |
Integer 0 to 1024 |
||
MESS:SUBF_X5 |
Integer 0 to 1023 |
||
MESS:SUBF_Y5 |
Integer 0 to 1023 |
||
MESS:SUBF_DX5 |
Integer 0 to 1024 |
||
MESS:SUBF_DY5 |
Integer 0 to 1024 |
||
MESS:CRITOPNV |
Integer 0 or 1 |
||
MESS:JAILBARS |
Integer 0 or 1 |
||
MESS:JB_X0 |
Integer 0 to 1023 |
||
MESS:JB_X1 |
Integer 0 to 1023 |
||
MESS:JB_SPACE |
Integer 0 to 1023 |
||
BAND_NAME |
"Latitude,
planetocentric, deg N" |
||
Table 3-9. MDIS-specific values for DDR label keywords.
MDIS near-nadir NAC and WAC 750-nm filter imaging of Mercury is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (BDRs) with incidence angles optimized in version 0 to be near 68¡ and in versions 1 and 2 to be near 74¡. Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the basemap imaging campaign; versions 1 and 2 contain data with appropriate illumination from any campaign.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS BDR products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = BDR
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_BDR_256PPD_H03NE0.IMG
For this image:
á Product type = BDR (BDR)
á Resolution = 256 pixels/degree (256PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 0
The BDR directory, present in the BDR archive volume, contains MDIS Map Projected Basemap Reduced Data Records (BDRs). The BDRs are organized into subdirectories based on the Mercury Chart containing the BDR. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.
Quadrangle1 |
Subdirectory name |
Latitude (degrees) |
Longitude (deg. east) |
H-1 Borealis |
H01 |
65 to 90 |
0 to 360 |
H-2 Victoria |
H02 |
22.5 to 65 |
270 to 360 |
H-3 Shakespeare |
H03 |
22.5 to 65 |
180 to 270 |
H-4 Raditladi (Liguria) |
H04 |
22.5 to 65 |
90 to 180 |
H-5 Hokusai (Apollonia) |
H05 |
22.5 to 65 |
0 to 90 |
H-6 Kuiper |
H06 |
-22.5 to 22.5 |
288 to 360 |
H-7 Beethoven |
H07 |
-22.5 to 22.5 |
216 to 288 |
H-8 Tolstoj |
H08 |
-22.5 to 22.5 |
144 to 216 |
H-9 Eminescu (Solitudo Criophori) |
H09 |
-22.5 to 22.5 |
72 to 144 |
H-10 Derain (Pieria) |
H10 |
-22.5 to 22.5 |
0 to 72 |
H-11 Discovery |
H11 |
-65 to -22.5 |
270 to 360 |
H-12 Michelangelo |
H12 |
-65 to -22.5 |
180 to 270 |
H-13 Neruda (Solitudo Persephones) |
H13 |
-65 to -22.5 |
90 to 180 |
H-14 Debussey (Cyllene) |
H14 |
-65 to -22.5 |
0 to 90 |
H-15 Bach |
H15 |
-90 to -65 |
0 to 360 |
Table
3-10. Latitude and longitude limits of Mercury Charts.
1Parenthetical names are defunct for quadrangles not imaged by a
spacecraft prior to MESSENGER.
A BDR:
á Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.
á Represents one latitude-longitude bin in a global map.
á Contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) BDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒBDR metricÓ is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the BDR products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for a BDR, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample BDR labels can be found in Appendix E. Table 3-11 below lists MDIS-specific values for BDR label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_BDR |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
ÒREFLECTANCE 750NMÓ ÒOBSERVATION IDÓ ÒBDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ |
Table 3-11. MDIS-specific values for BDR label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
MDIS 8-color imaging of Mercury is mosaicked into 54 non-overlapping, 64 pixel/degree tiles (MDRs). Each tile corresponds to the NW, NE, SW, or SE quadrant of one of the pre-existing Mercury non-polar charts, or one of the two polar charts.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS MDR products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles will be named based on the quadrant of the Mercury chart they span. The nominal version of each tile is named as follows.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = MDR
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_MDR_064PPD_H03NE0.IMG
For this image:
á Product type = MDR (MDR)
á Resolution = 64 pixels/degree (064PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 0
A redundant tile covering the south polar region has a modified nomenclature, reflecting that it includes reduced-resolution (to 2700 m/pixel) images in order to fill a coverage gap in the nominal tile:
MDIS_MDR_064PPD_2700_H15SP1.IMG
The MDR directory, present in the MDR archive volume, contains 8-color MDIS Map Projected Multispectral Reduced Data Records (MDRs). The MDRs are organized into subdirectories based on the Mercury Chart containing the MDR. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.
An MDR:
á Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ at a resolution of 64 pixels per degree (~665 m/pixel at the equator).
á Represents one latitude-longitude bin in a global color map.
á Is composed of up to 8 bands corresponding to the 8 of the 11 WAC filters. The 8 are selected on account of limitations in MESSENGER solid-state recorder space, and more or less evenly sample the spectral range of MDIS.
á Version 0, 1 or 2 contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) MDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒMDR metricÓ is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).
á Version 3 or 4 contains 9 backplanes for the reference 750-nm band: (a) image count, and (b-i) standard deviation of the values used to determine average normalized I/F in each of the 8 bands (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the MDR products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately 665.3 meters/pixel for an MDR, which achieves close to the desired 64 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample MDR labels can be found in Appendix F. Table 3-12 below lists MDIS-specific values for MDR label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_MDR |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
Product Version ID 0 or 1: "WAC FILTER 6 430 BP 40" "WAC FILTER 3 480 BP 10" "WAC FILTER 4 560 BP 5" "WAC FILTER 5 630 BP 5" "WAC FILTER 7 750 BP 5" "WAC FILTER 12 830 BP 5" "WAC FILTER 10 900 BP 5" "WAC FILTER 9 1000 BP 15" Product Version ID 0: ÒOBSERVATION IDÓ ÒMDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ Product Version ID 1: "IMAGE COUNT" "STDEV WAC FILTER 6 430 BP 40" "STDEV WAC FILTER 3 480 BP 10" "STDEV WAC FILTER 4 560 BP 5" "STDEV WAC FILTER 5 630 BP 5" "STDEV WAC FILTER 7 750 BP 5" "STDEV WAC FILTER 12 830 BP 5" "STDEV WAC FILTER 10 900 BP 5" "STDEV WAC FILTER 9 1000 BP 15" |
Table 3-12. MDIS-specific values for MDR label keywords. Product version IDs refer to the two distinct file structures used over the history of the product. Reflectance is at i=30¡, e=0¡, g=30¡.
The 3-color MDIS image mosaic of Mercury's northern and equatorial latitudes is divided into non-overlapping, 128 pixel/degree tiles (MD3s). Each tile corresponds to the NW, NE, SW, or SE quadrant of one of the pre-existing Mercury non-polar charts, or the north polar chart.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS MD3 products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = MD3
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_MD3_128PPD_H03NE0.IMG
For this image:
á Product type = MD3 (MD3)
á Resolution = 128 pixels/degree (128PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 0
The MD3 directory, present in the MD3 archive volume, contains 3-color MDIS Map Projected Multispectral Reduced Data Records (MD3s). The MD3s are organized into subdirectories based on the Mercury Chart containing the MDR. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10. For MD3s there is no H15 subdirectory because the 3-color mapping campaign did not include that portion of Mercury.
An MD3:
á Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ at a resolution of 128 pixels per degree (~332 m/pixel at the equator).
á Represents one latitude-longitude bin in a regional color map.
á Is composed of up 3 bands corresponding to 3 of the 11 WAC filters. The 3 sample albedo and spectral slope variations over the spectral range of MDIS; the fewer filters than in the 8-color map is for data volume management during acquisition, due to spatial sampling >2 times smaller in scale.
á Version 0 contains 5 backplanes for the reference 750-nm band: (a) observation id, (b) MDR metric, (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒMDR metricÓ is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3), modified for the different limiting spatial resolution.
á Version 1 or 2 contains 4 backplanes for the reference 750-nm band: (a) image count, and (b-d) standard deviation of the values used to determine average normalized I/F in each of the 3 bands (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the MDR products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately 332.7 meters/pixel for an MD3, which achieves close to the desired 128 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample MD3 labels can be found in Appendix G. Table 3-13 below lists MDIS-specific values for MD3 label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_MD3 |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
Product Version ID 0 or 1: "WAC FILTER 6 430 BP 40" "WAC FILTER 7 750 BP 5" "WAC FILTER 9 1000 BP 15" Product Version ID 0: ÒOBSERVATION IDÓ ÒMDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ Product Version ID 1: "IMAGE COUNT" "STDEV WAC FILTER 6 430 BP 40" "STDEV WAC FILTER 7 750 BP 5" "STDEV WAC FILTER 9 1000 BP 15" |
Table 3-13. MDIS-specific values for MD3 label keywords. Product version IDs refer to the two distinct file structures used over the history of the product. Reflectance is at i=30¡, e=0¡, g=30¡.
MDIS 5-color imaging of Mercury's north polar latitudes is mosaicked into a single 128 pixel/degree tile (MP5). This tile corresponds to the pre-existing Mercury chart H01, plus the northern part of the chart to the immediate south, H02-H05.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS MP5 products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = MP5
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_MP5_128PPD_H01NP1.IMG
For this image:
á Product type = MP5 (MP5)
á Resolution = 128 pixels/degree (128PPD)
á Mercury chart = Borealis (H01)
á Quadrant = North Polar (NP)
á Version = 1
The MP5 directory, present in the MP5 archive volume, contains the 5-color MDIS Map Projected Multispectral Reduced Data Record (MP5). MP5 files are located in a subdirectory based on Mercury Chart. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10. The center latitude and center longitude of the MP5 is located in H01 so only that directory is populated.
An MP5:
á Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a multispectral map tile.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ at a resolution of 128 pixels per degree (~332 m/pixel at the equator).
á Is composed of up to 5 bands corresponding to 5 of the 11 WAC filters. The 5 filters provide improved spectral sampling of color variations in the Northern Volcanic Plains geologic unit compared to the MD3 data product, and twice the spatial resolution of the MDR data product.
á Version 1 or 2 contains 6 backplanes for the reference 750-nm band: (a) image count, and (b-f) standard deviation of the values used to determine average normalized I/F in each of the 5 bands (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. The polar tile is in polar stereographic projection.
See section 2.5.2.3 for a description of how the MP5 products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using POLAR STEREOGRAPHIC for the MP5 product.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. A sample MP5 label can be found in Appendix H. Table 3-14 below lists MDIS-specific values for MP5 label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_MP5 |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
"WAC FILTER 6 430 BP 40" "WAC FILTER 4 560 BP 5" "WAC FILTER 7 750 BP 5" "WAC FILTER 12 830 BP 5" "WAC FILTER 9 1000 BP 15" "IMAGE COUNT" "STDEV WAC FILTER 6 430 BP 40" "STDEV WAC FILTER 4 560 BP 5" "STDEV WAC FILTER 7 750 BP 5" "STDEV WAC FILTER 12 830 BP 5" "STDEV WAC FILTER 9 1000 BP 15" |
Table 3-14. MDIS-specific values for MP5 label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
MDIS near-nadir NAC and WAC 750-nm filter high incidence angle imaging of Mercury illuminated from the east is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (HIEs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the high-incidence angle imaging campaign, optimized to include imaging with incidence angles near 78¡; version 1 contains data with appropriate illumination from any campaign, again optimized to include imaging with incidence angles near 78¡; version 2 differs from version 1 in being optimized to include imaging with incidence angles near 86¡.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS HIE products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = HIE
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_HIE_256PPD_H03NE0.IMG
For this image:
á Product type = HIE (HIE)
á Resolution = 256 pixels/degree (256PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 0
The HIE directory, present in the HIE archive volume, contains MDIS Map Projected High Incidence Angle Basemap Illuminated from the East Reduced Data Records (HIEs). The HIEs are organized into subdirectories based on the Mercury Chart containing the HIE. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.
An HIE:
á Consists of a mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the high-incidence angle campaign and having a value of SUB_SOLAR_LONGITUDE located eastward of the image CENTER_LONGITUDE (section 2.3.3.1) are included. For version 1 or 2, images from other campaigns with suitable illumination are included.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.
á Represents one latitude-longitude bin in a global map.
á Contains 5 backplanes: (a) observation id, (b) the BDR metric adjusted for the optimal incidence angle to be 78¡ or 86¡ depending on the HIE version, (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒBDR metricÓ is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the HIE products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for an HIE, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample HIE labels can be found in Appendix I. Table 3-15 below lists MDIS-specific values for HIE label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_HIE |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
ÒREFLECTANCE 750NMÓ ÒOBSERVATION IDÓ ÒBDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ |
Table 3-15. MDIS-specific values for HIE label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
MDIS near-nadir NAC and WAC 750-nm filter high incidence angle imaging of Mercury illuminated from the west is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (HIWs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Version 0 contains only data from the high-incidence angle imaging campaign, optimized to include imaging with incidence angles near 78¡; version 1 contains data with appropriate illumination from any campaign, again optimized to include imaging with incidence angles near 78¡; version 2 differs from version 1 in being optimized to include imaging with incidence angles near 86¡.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS HIW products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = HIW
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_HIW_256PPD_H03NE0.IMG
For this image:
á Product type = HIW (HIW)
á Resolution = 256 pixels/degree (256PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 0
á Is accompanied by a label.
The HIW directory, present in the HIW archive volume, contains MDIS Map Projected High Incidence Angle Basemap Illuminated from the West Reduced Data Records (HIWs). The HIWs are organized into subdirectories based on the Mercury Chart containing the HIW. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.
An HIW:
á Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the high-incidence angle campaign and having a value of SUB_SOLAR_LONGITUDE located westward of the image CENTER_LONGITUDE (section 2.3.3.1) are included. For version 1 or 2, images from other campaigns with suitable illumination are included.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.
á Represents one latitude-longitude bin in a global map.
á Contains 5 backplanes: (a) observation id, (b) the BDR metric adjusted for the optimal incidence angle to be 78¡ or 86¡ depending on the HIE version , (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒBDR metricÓ is a metric describing the resolution and illumination of data used to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the HIW products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately 166.3 meters/pixel for an HIW, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample HIW labels can be found in Appendix J. Table 3-16 below lists MDIS-specific values for HIW label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_HIW |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
ÒREFLECTANCE 750NMÓ ÒOBSERVATION IDÓ ÒBDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ |
Table 3-16. MDIS-specific values for HIW label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
MDIS near-nadir NAC and WAC 750-nm filter low incidence angle imaging of Mercury with the lowest available incidence angles is mosaicked into 54 non-overlapping, 256 pixel/degree tiles (LOIs). Each tile corresponds to the NW, NE, SW, or, SE quadrant of one of the pre-existing Mercury non-polar charts or one of the two polar charts. Versions 1 and 2 contain data from the low-incidence angle albedo campaign plus images with appropriate illumination from any campaign.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS LOI products have a Ò22.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Map tiles are named based on the quadrant of the Mercury chart they span.
Format: "MDIS_ppp_rrrPPD_Hxxddv.ext"
ppp = product type = LOI
rrr = resolution in pixels/degree (PPD)
Hxx = Mercury chart designation
dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_LOI_256PPD_H03NE1.IMG
For this image:
á Product type = LOI (LOI)
á Resolution = 256 pixels/degree (256PPD)
á Mercury chart = Shakespeare (H03)
á Quadrant = Northeast (NE)
á Version = 1
The LOI directory, present in the LOI archive volume, contains MDIS Map Projected Low Incidence Angle Basemap Reduced Data Records (LOIs). The LOIs are organized into subdirectories based on the Mercury Chart containing the LOI. Latitude and longitude limits of Mercury Charts and the corresponding subdirectory names are given in Table 3-10.
An LOI:
á Consists of an uncontrolled mosaic of map-projected, photometrically normalized I/F CDRs collectively forming a monochrome map tile. For version 0, only those images taken as part of the near-nadir part of the low-incidence angle campaign are included. For version 1 or 2, images from other campaigns with suitable illumination are included.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ sampled at a scale of 256 pixels per degree (~166 meters/pixel at the equator), composed of WAC filter 7 (G) (750 BP 5) and NAC images.
á Represents one latitude-longitude bin in a global map.
á Contains 5 backplanes: (a) observation id, (b) the MDR metric adjusted for the different limiting resolution, (c) solar incidence angle, (d) emission angle, and (e) phase angle. ÒMDR metricÓ is a metric describing the resolution and illumination of data used, to determine where and whether to overlay future imaging coverage (see section 2.5.2.3).
Versions increment on reprocessing or addition of new data. Polar tiles are in polar stereographic projections, other tiles in equirectangular projection.
See section 2.5.2.3 for a description of how the LOI products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using EQUIRECTANGULAR for tiles centered equatorward of 65 degrees latitude, and POLAR STEREOGRAPHIC centered poleward of 65 degrees latitude.
For the latitude band projected equirectangularly, the CENTER_LATITUDE of projection is the equatorward boundary of each band to minimize 'distortion.' The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
lat = y / (A_AXIS_RADIUS * 1000)
lon = CENTER_LONGITUDE +
180/pi * (x/(A_AXIS_RADIUS * 1000 * cos(CENTER_LATITUDE*pi/180))
Note that integral values of line and sample correspond to the center of a pixel. Lat and lon are the latitude and longitude of a given location on the surface, east positive.
MAP_SCALE= the map scale in meters per pixel, approximately166.3 meters/pixel for an LOI, which achieves close to the desired 256 pixels/degree at the CENTER_LATITUDE.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, origin is the equatorward edge of the map tile. The value of LINE_PROJECTION_OFFSET is positive for images starting north of the equator and is negative for images starting south of the equator.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). For an EQUIRECTANGULAR map projection, the value of SAMPLE_PROJECTION_OFFSET is positive for images starting to the west of the projection longitude and is negative for images starting to the east of the projection longitude.
MAP_RESOLUTION is measured in pixels/degree.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
For the latitude bands projected polar stereographically, projection is centered on the north or south pole. Lines of longitude extend radially from the pole and parallels of latitude are concentric circles around the center. In the north, longitude 0 extends straight down from the center and longitude 90 East extends to the right. In the south, longitude 0 extends straight up from the center, and longitude 90 East extends to the right. Thus in any given tile, north is at a variable orientation in LINE-SAMPLE space. The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is the reference pole)
c = 2 * atan(rho/(2*(A_AXIS_RADIUS*1000)))
lon = CENTER_LONGITUDE + (atan2(x,-y) * 180/pi) (northern hemisphere)
lon = CENTER_LONGITUDE + (atan2(x,y) * 180/pi) (southern hemisphere)
lat = 180/pi * arcsin[cos(c)*sin(CENTER_LATITUDE*pi/180) +
(y*sin(c)*cos(CENTER_LATITUDE*pi/180)/rho)]
where lat = latitude in degrees and lon = longitude in degrees.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array).
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample LOI labels can be found in Appendix K. Table 3-17 below lists MDIS-specific values for LOI label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_LOI |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
ÒREFLECTANCE 750NMÓ ÒOBSERVATION IDÓ ÒMDR METRICÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ |
Table 3-17. MDIS-specific values for LOI label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
Key types of MDIS targeted observations are mosaicked into Regional Targeted Mosaics (RTMs). Unlike the global and regional mapping campaign map products, which are divided into a regular pattern of tiles based on Mercury Charts, most RTMs are based on one MESSENGER Science Team-Defined "region of interest" that is the target of the images. That region of interest is encoded in the keyword SITE_ID and also appears in the PRODUCT_ID. It is referenced in a list of site IDs explaining the science motivation for their targeting, found in the EXTRAS directory. In addition, two RTMs are based on regions of interest defined after imaging was acquired and initial BDRs and MDRs were created and delivered: the Caloris impact basin and the unnamed, mostly buried "b30" impact basin.
The file names developed for this PDS archive are restricted to a maximum 36-character base name and 3 character extension name with a period separating the file and extension names. Also known as the Ò36.3Ó format, this is compliant with the ISO 9660 Level 2 specification (maximum of 40 characters), which is required by PDS. The MDIS RTM products have a Ò29.3Ó format and thus remain within the PDS specification parameters. Below is the detailed naming convention for this dataset.
Most RTM products are named based on their SITE_ID, OBSERVATION_ID, and image contents they contain.
Format: "MDIS_ppp_cbb_siteid_observationid_v.ext"
ppp = product type = RTM
c = camera (W WAC or N NAC)
bb = bands (01, 03, 08, 11 depending on type of observation)
siteid = a 6-digit integer giving the unique SITE_ID of the region covered by the product
observationid = image observation ID of the first image (lowest ID)
v = version number
ext = IMG for the multiband image, LBL for the detached label.
The following is an example file name with a description of the individual components:
MDIS_RTM_N01_000276_1214047_1.IMG
For this image:
á Product type = RTM (RTM)
á Camera = NAC (N)
á Bands = 1 (01)
á SITE_ID = 276 (000276)
á OBSERVATION_ID = 1214047
á Version = 1
3-color RTMs covering Caloris and "b30" have a modified nomenclature, reflecting their organization around regions of interest defined geographically after-the-fact:
MDIS_RTM_W03_CALORIS_1.IMG
MDIS_RTM_W03_B30_1.IMG
The RTM directory, present in the RTM archive volume, contains MDIS Map Projected Regional Targeted Mosaics (RTMs). The RTMs whose nomenclature contains a site ID are organized into subdirectories based on the camera/band (e.g., MDIS_RTM_N01) and then within those subdirectories, by year and day of year on which the images were acquired (e.g., 2014_346), referencing the start image. The RTMs whose nomenclature contains "CALORIS" or "B30" reside within the "MDIS_RTM_W03" directory, in subdirectories called "CALORIS" and "B30" respectively. The structure is generalized to allow for the fact that some targeted observations were taken with the NAC and some with the WAC, and that the number of WAC bands depends on the purpose of the observation (see sections 2.3.1.5, 2.3.1.6, 2.3.1.7, and 2.3.3.5), while also allowing for the ad hoc Caloris and b30 products.
An RTM:
á Consists of a mosaic of map-projected, photometrically normalized I/F CDRs. Only those images taken as part of coverage of a specific SITE_ID are included.
á Contains image data in I/F corrected photometrically to i=30¡, e=0¡, g=30¡ sampled at variable pixel scale depending on the observation.
á May contain 3 to 11 bands of WAC images or 1 band with one or more NAC images.
á Is a self-contained product and not part of a larger global map.
á NAC mosaics contain 4 backplanes: (a) observation id, (b) solar incidence angle, (c) emission angle, and (d) phase angle.
á WAC color products based on site ID contain 3 backplanes for the reference 750-nm band: (a) solar incidence angle, (b) emission angle, and (c) phase angle. WAC 3-color products for Caloris and b30 contain 4 backplanes for the reference 750-nm band: (a) image count, and (b-d) standard deviation of the values used to determine average normalized I/F in each of the 3 bands.
Versions increment on reprocessing. All products are in orthographic projection.
See section 2.5.2.3 for a description of how the RTM products are generated.
The projection convention adopted by the MESSENGER project is planetocentric and positive east. Prior to delivery 15, the MESSENGER team used the prime meridian and other Mercury coordinate system values described in Archinal et al. [2009, Applicable Document 12] with Mercury radii of 2440 km for products provided to PDS. For deliveries 15 and 16, the MESSENGER team used the Mercury coordinate system values contained in the SPICE Planetary Constants Kernel provided to NAIF by MESSENGER with delivery 15 which included updates to the Mercury prime meridian, rotation rate, and radii (2439.4 km). The projection varies with latitude, using ORTHOGRAPHIC for all RTM products.
The CENTER_LATITUDE and CENTER_LONGITUDE are at the origin of the Orthographic projection. CENTER_LATITUDE is also the latitude of the central point of the Orthographic projection.
The transformation from line and sample coordinates to planetocentric latitude and longitude is given by these equations.
x = (SAMPLE - SAMPLE_PROJECTION_OFFSET - 0.5) * MAP_SCALE
y = (LINE - LINE_PROJECTION_OFFSET - 0.5) * -1 * MAP_SCALE
rho = sqrt(x^2 + y^2)
(if rho=0, lat,lon is CENTER_LATITUDE,CENTER_LONGITUDE)
c = arcsin[rho/(A_AXIS_RADIUS * 1000)]
clatr = CENTER_LATITUDE * pi/180
lat = arcsin[cos(c) * sin(clatr) + (y * sin(c) * cos(clatr)/rho)]
lon = CENTER_LONGITUDE +
arctan[x*sin(c)/(rho*cos(clatr)*cos(c) - y*sin(clatr)*sin(c))]
where lat = latitude and lon = longitude, east positive.
LINE_PROJECTION_OFFSET = the line offset value of the map projection origin from the line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). This is equivalent to the line number of at the center of the map minus the line number in the upper left corner.
SAMPLE_PROJECTION_OFFSET = the sample offset value of the map projection origin from line and sample 1,1 (line and sample 1,1 is considered the upper left corner of the digital array). This is equivalent to the sample number of at the center of the map minus the sample number in the upper left corner.
MAP_SCALE is measured in m/pixel.
There are four PDS parameters that specify the latitude and longitude boundaries of an image. MAXIMUM_LATITUDE and MINIMUM_LATITUDE specify the latitude boundaries of the image, and EASTERNMOST_LONGITUDE and WESTERNMOST_LONGITUDE specify the longitudinal boundaries of the map.
Definitions of other mapping parameters can be found in the PDS Data Dictionary.
The detached label conforms to PDS version 3.8 standards (Applicable Document 3). The purpose of the PDS label is to describe the data product. A single label points to the IMG file. Sample RTM labels can be found in Appendix L. Table 3-18 below lists MDIS-specific values for RTM label keywords. See Appendix B for keyword descriptions.
Keyword |
Valid Values |
INSTRUMENT_ID |
ÒMDIS-WACÓ ÒMDIS-NACÓ |
PRODUCT_TYPE |
MAP_PROJECTED_RTM |
UNIT |
ÒReflectanceÓ |
BAND_NAME |
"WAC FILTER 6 430 BP 40" "WAC FILTER 3 480 BP 10" "WAC FILTER 4 560 BP 5" "WAC FILTER 5 630 BP 5" "WAC FILTER 1 700 BP 5" "WAC FILTER 7 750 BP 5" "WAC FILTER 12 830 BP 5" "WAC FILTER 10 900 BP 5" "WAC FILTER 8 950 BP 7" "WAC FILTER 9 1000 BP 15" "WAC FILTER 11 1020 BP 40" ÒREFLECTANCE 750NMÓ ÒOBSERVATION IDÓ "SOLAR INCIDENCE ANGLE" "EMISSION ANGLE" "PHASE ANGLEÓ "IMAGE COUNT" "STDEV WAC FILTER 6 430 BP 40" "STDEV WAC FILTER 7 750 BP 5" "STDEV WAC FILTER 9 1000 BP 15" |
Table 3-18. MDIS-specific values for RTM label keywords. Reflectance is at i=30¡, e=0¡, g=30¡.
The Calib directory (Table 3-19) contains the calibration files used in the processing of the raw data to create the CDRs or needed to use the data products on the volume. The EDR and CDR volumes contain all of the files listed in the table. The MD3, MDR, MP5, and RTM volumes contain only bandpass filters of NAC or WAC bands present in the data, that may be useful for analysis of the respective data.
File Name |
Req.? |
File Contents |
|
CALINFO.TXT |
Yes |
Describes the contents of this directory. |
|
LUT_INVERT/ |
No |
This directory contains the inverse lookup table required for inverting 8-bit images into their original 12-bit format. |
|
|
MDISLUTINV_0.TAB |
No |
This file contains 8-bit values, and the 12-bit values to which they correspond. There is one set of 12-bit values for each of the eight available lookup tables in the instrument. |
MDISLUTINV_0.LBL |
No |
The label that describes the preceding file. |
|
DARK_MODEL/ |
No |
This directory contains tables of coefficients needed to model the dark level in the NAC or WAC, with on-chip pixel binning turned on or not. |
|
|
MDIScam_bining_DARKMODEL_v.TAB |
No |
cam = camera, NAC or WAC bining = binning, NOTBIN or BINNED v = version number, 0-9, a-z |
MDIScam_bining_DARKMODEL_v.LBL |
No |
Detached labels describing the tables. |
|
FLAT/ |
No |
This directory contains flat-field images which correct for response variations from pixel to pixel and across the CCD. There are separate files for each of the 12 WAC filters and for the NAC, with on-chip pixel binning turned on or not. |
|
|
MDISWAC_bining_FLAT_FILT_nn_v.FIT |
No |
bining = binning, NOTBIN or BINNED nn = filter number, 1-12 v = version number, 0-9, a-z |
MDISWAC_bining_FLAT_FILT_nn_v.LBL |
No |
Detached labels describing the WAC flat-field images. |
|
MDISNAC_bining_FLAT_v.FIT |
No |
bining = binning, NOTBIN or BINNED v = version number, 0-9, a-z |
|
MDISNAC_bining_FLAT_v.LBL |
No |
Detached labels describing the NAC flat-field images. |
|
RESPONSIVITY/ |
No |
This directory contains tables of coefficients used to convert corrected DN to units of radiance. There are separate tables for the WAC and NAC, with on-chip pixel binning turned on or not. |
|
|
MDIScam_bining_RESP_v.TAB |
No |
cam = camera, NAC or WAC bining = binning, NOTBIN or BINNED v = version number, 0-9, a-z |
MDIScam_bining_RESP_v.LBL |
No |
Detached labels describing the tables. |
|
CORRECT/ |
No |
This directory contains tables of coefficients used to correct the radiance conversion for effects of contamination of WAC optics. There is one table for the WAC. |
|
|
MDISWAC_CORRECT_v.TAB |
No |
v = version number, 0-9, a-z |
MDISWAC_CORRECT_v.LBL |
No |
Detached labels describing the tables. |
|
SOLAR/ |
No |
This directory contains tables of solar irradiance used to convert radiance to units of I/F. There are separate tables for the WAC and NAC. |
|
|
MDIScam_SOLAR_v.TAB |
No |
cam = camera, NAC or WAC v = version number, 0-9, a-z |
MDIScam_SOLAR_v.LBL |
No |
Detached labels describing the tables. |
|
SUPPORT/ |
No |
This directory contains characterizations of the instrument that are not part of the calibration process per se, but were used to derive the calibration files that are used. |
|
|
MDISLUTFWD_0.TAB |
No |
Contains the onboard forward lookup tables used optionally to convert 12-bit to 8-bit images. |
MDISLUTFWD_0.LBL |
No |
The label that describes the preceding file. |
|
|
MDISBPcf.TAB |
No |
Tables giving bandpasses for each WAC filter and for the NAC. c = N for NAC, W for WAC f = A through M for different filters For the NAC, f = M For the WAC, f = A for Filter 1, 700 BP 5; B for Filter 2, 700 BP 600; C for Filter 3, 480 BP 10; D for Filter 4, 560 BP 5; E for Filter 5, 630 BP 5; F for Filter 6, 430 BP 40; G for Filter 7, 750 BP 5; H for Filter 8, 950 BP 7; I for Filter 9, 1000 BP 15; J for Filter 10, 900 BP 5; K for Filter 11, 1020 BP 40; L for Filter 12, 830 BP 5 |
MDISBPWa.LBL |
No |
The label that describes the preceding file. |
Table 3-19: Calib Directory Contents.
The GEOMETRY directory, included on the EDR and CDR volumes only, contains the file GEOMINFO.TXT that points to and describes the function of each SPICE kernel relevant to MDIS.
The EXTRAS directories contain several types of ancillary files: browse versions of data products, shape files, tabulated data on site IDs, and empirical corrections to map-projected, mosaicked products applied on top of the formal radiometric calibration and photometric normalizations described in section 2.5.2. The file EXTRINFO.TXT describes the contents of the directory.
Browse products are synoptic versions of map-projected data products that help to identify products of interest. Each set of browse products is organized into a BROWSE subdirectory within the EXTRAS directory within the BDR, MDR, MD3, MP5, HIE, HIW, LOI, and RTM archives. Within each BROWSE subdirectory, the organization of subdirectories parallels that of the directories containing data products (e.g., BDR, MDR, etc.). All browse products have the same line and sample dimensions, pixel scale, map projection, and nomenclature as the parent data products. Browse products are formatted in a Portable Network Graphics (PNG) format.
BDR, HIE, HIW, and LOI browse products are single-band gray-scale images whose parent data are a mix of NAC images and WAC 750-nm images. A different uniform, global stretch of reflectance at i=30¡, e=0¡, g=30¡ to an 8-bit integer is applied to each product type.
MDR, MD3, and MP5 browse products are 3-band RGB images, each constructed using data from WAC filters 9, 7, and 6 (1000, 750, and 430 nm) in the red, green and blue image planes. All three of these filters are present in all three of the data product types. A uniform, global stretch of reflectance at i=30¡, e=0¡, g=30¡ to an 8-bit integer is applied to each product type.
RTM browse products come in two types. Those constructed from 3-, 8-, or 11-color WAC targeted observations are 3-band RGB images, constructed using data from WAC filters 9, 7, and 6 (1000, 750, and 430 nm) in the red, green and blue image planes. For these color products, a local stretch of reflectance at i=30¡, e=0¡, g=30¡ to an 8-bit integer is applied to individual RTM products. Products constructed from NAC images are single-band gray-scale images. For these monochrome NAC products, a uniform, global stretch of reflectance at i=30¡, e=0¡, g=30¡ to an 8-bit integer is applied.
The EXTRAS directory in the BDR, HIE, HIW, LOI, MDR, MD3, MP5, and RTM archives contains shape files that record for any appropriate MDIS image its coverage of Mercury during the orbital mission. In addition to the spatial coverage information, each record has attributes describing the image that are extracted from the PDS labels.
In the archives containing monochrome maps (i.e., BDR, HIE, HIW, LOI, RTM), shape files contained in the subdirectory img_footprints/cumulative include all images covering at least part of Mercury that were acquired during the orbital mission. Those archives containing global monochrome map products (i.e., BDR, HIE, HIW, LOI,) contain in the subdirectory img_footprints/ controlled_only shape files that cover the subset of images that are in the USGS global control set.
Archives that include color map products (MDR, MD3, MP5, RTM) contain a subdirectory with shape files that describe the areas of overlapping coverage within individual sets of 3, 5, or 8 filters. In the MDR archive, the subdirectory CLR_FOOTPRINTS/MDR contains shape files for the 8-color image sets used to build the maps contained in the MDR archive. In the MD3 archive, the subdirectory CLR_FOOTPRINTS/MD3 contains shape files for the 3-color image sets used to build the maps contained in the MD3 archive; the subdirectory CLR_FOOTPRINTS/MD3/H01 contains shape files for the 3-color campaign color set used for north polar map tile H01 in the MD3 archive. In the MP5 archive, the subdirectory CLR_FOOTPRINTS/MP5 contains shape files for the minimized phase angle 5-color image sets used to build the maps contained in the MP5 archive. In the RTM archive, the EXTRAS subdirectory CLR_FOOTPRINTS/CLR_TARGETS contains separate shape files for 3-, 8-, and 11-color image sets used to build multispectal maps of regions of interest each linked by a discrete SIDE_ID. The subdirectories CLR_FOOTPRINTS/CLR_REGIONS contain separate shape files for 3-color image sets used to build the b30 and Caloris 3-color RTMs.
The following image polygon attributes are contained in the shape files in the above directories:
á obs_id[INT] -- image observation ID
á filename -- image filename
á ydoy_path -- Year, Day of Year storage path. i.e. (2015_001)
á obs_type -- text description of intent of image
á site_id -- for targeted images, the ID of the site of interest
á instr_id -- imager, MDIS-NAC or MDIS-WAC
á dqi -- data quality ID, as defined in the MDIS EDR Data Product SIS
á phase_name -- Name of mission phase. e.g. "MERCURY ORBIT YEAR 4"
á start_time -- Image exposure start time
á seq_name -- Unused for MESSENGER Mercury orbit phases
á sc_alt[FLOAT] -- spacecraft altitude
á met_exp[FLOAT] -- MET assigned to exposure (not the exposure start)
á det_temp[FLOAT] -- Detector temperature in degC
á exp_drtn[FLOAT] -- exposure duration in milliseconds
á filter_no[INT] -- filter number (1-12 for WAC, 0 for NAC)
á lines[INT] -- number of lines
á samples[INT] -- number of columns
á sat_pix[INT] -- number of saturated pixels
á center_lat[FLOAT] -- latitude of image center in degrees
á center_lon[FLOAT] -- longitude of image center in degrees
á slant_d[FLOAT] -- distance from camera to intercept of image center in km
á smear_mag[FLOAT] -- smear magnitude in pixels
á i_angle[FLOAT] -- solar incidence angle of image center in degrees
á p_angle[FLOAT] -- solar phase angle of image center in degrees
á e_angle[FLOAT] -- emission angle of image center in degrees
á hor_scale[FLOAT] -- horizontal pixel scale of image center in meters
á ver_scale[FLOAT] -- vertical pixel scale of image center in meters
For images that are candidates for inclusion in global map products, the following quality scores used for stacking images into a map (lower is better) are also included. These are based on combinations of image resolution, incidence and emission angles:
á bdr_metric[FLOAT] -- alternate for monochrome map (68deg incidence)
á bdr_met2[FLOAT] -- alternate formula monochrome map
á mdr_metric[FLOAT] -- 8-color map
á hsi_metric[FLOAT] -- high-incidence map
á alb_metric[FLOAT] -- albedo, or low-incidence map
á md3_metric[FLOAT] -- 3-color map
á bdr_i71met[FLOAT] -- alternate for monochrome map (71deg incidence)
á bdr_i74met[FLOAT] -- used for BDR monochrome map (74deg incidence)
á bdr_i74me2[FLOAT] -- alternate for monochrome map (74deg incidence)
á bdr_i77met[FLOAT] -- alternate for monochrome map (77deg incidence)
á hii_i80met[FLOAT] -- alternate for high-incidence mono-maps (80deg incidence)
á hii_i83met[FLOAT] -- alternate for high-incidence mono-maps (83deg incidence)
á hii_i86met[FLOAT] -- used for HIE and HIW maps (86deg incidence)
The following information is also included, which captures instrument set-up at the time of data acquisition and other measures of image geometry:
á piv_goal[FLOAT] -- goal angle for pivot platform in counts (when applicable)
á piv_pos[FLOAT] -- pivot angle for pivot platform in counts
á piv_read[FLOAT] -- pivot resolver angle in counts
á comp12_8[FLOAT] -- 12 to 8 bit compression flag
á comp_alg[FLOAT] -- 8 bit lookup table number used for compression
á smear_az[FLOAT] -- smear azimuth in degrees
á north_az[FLOAT] -- north azimuth in degrees
á sub_sc_az[FLOAT] -- sub-spacecraft point azimuth in degrees
á sub_sol_az[FLOAT] -- sub-solar point azimuth in degrees
á wvl_ratio[INT] -- wavelet compression ratio
á sub_sc_lat[FLOAT] -- sub-spacecraft point latitude in degrees
á sub_sc_lon[FLOAT] -- sub-spacecraft point longitude in degrees
á subsol_lat[FLOAT] -- sub-solar point latitude in degrees
á subsol_lon[FLOAT] -- sub-solar point longitude in degrees
á subsol_ga[FLOAT] -- sub-solar ground azimuth computed using sub-solar azimuth and north azimuth
á subsol_ga2[FLOAT] -- sub-solar ground azimuth computed using image center lat/lon and sub-solar lat/lon
Color-set areas-of-overlap attributes contained in shapefiles include the following:
á start_obs[INT] -- first observation ID (in time) for this set
á obs_list -- list of all observation IDs in the set
á src_shp -- image footprint shapefile used to generate this record
á seq_type -- campaign the sequence belongs to, i.e. MDR WAC 8-bands
á seq_length[INT] -- number of images in colorset sequence
á seq_hscale[FLOAT] -- horizontal pixel scale of first image
á seq_i[FLOAT] -- solar incidence of center pixel in first image
á seq_p[FLOAT] -- solar phase of center pixel in first image
á seq_e[FLOAT] -- emission angle of center pixel in first image
á mdr_metric[FLOAT] -- 8-color map quality score for first image
á site_id[INT] -- for targeted images, the ID of the site of interest
á det_temp[FLOAT] -- detector temperature of first image in degC
The EXTRAS directory in the RTM archive also contains a list of all SITE_IDs targeted by MDIS or other instruments, describing their latitude/longitude coordinates and the motivation for their targeting. This list is derived directly from the list of observing requests for targeted images compiled by the MESSENGER science and operations team and the original file had an uneven level of detail. The format of the file name is MESSENGER_TARGET_DATABASE.XLS. Columns in the list of SITE_IDs include the following:
á site_name -- an alphanumeric name assigned to the site
á Site ID -- an integer designation of the site ID
á Rationale -- an explanation of the scientific rationale for targeting the site
á Type -- the set of MESSENGER instrument data desired for collection to sample the site
The extras directory in the RTM archive contains image files sharing the format of flat-field files that include a spatial (image line and column) component to the empirical calibration correction Correct (f,MET) described in section 2.5.2. This spatial correction is only easily derived for the "B30" and "CALORIS" 3-color RTM mosaics by virtue of the large amounts of image overlap. There is a separate correction for each mosaic, with file nomenclature as follows:
á B30.RATIO_CORRECTION_F.FIT
á B30.RATIO_CORRECTION_G.FIT
á B30.RATIO_CORRECTION_I.FIT
á CALORIS.RATIO_CORRECTION_F.FIT
á CALORIS.RATIO_CORRECTION_G.FIT
á CALORIS.RATIO_CORRECTION_I.FIT
Standard Integrated Software for Imagers and Spectrometers (ISIS) tools (http://isis.astrogeology.usgs.gov/) can be used to work with the data. ISIS has the ability to calibrate EDRs, incorporate related SPICE files, and map-project images. ISIS was also used to generate the global DEM onto which end-of-mission map products were projected, as described by Becker et al. (2016) [Applicable Document 15].
Environment for Visualizing Images (ENVI) software from Exelis, Inc. (http://www.exelisinc.com/solutions/ENVI/Pages/default.aspx) is widely used for analysis of multispectral data products such as MDRs, MD3s, MP5s, and WAC-derived RTMs.
PDS-labeled images and tables can be viewed with the program NASAView, developed by the PDS and available for a variety of computer platforms from the PDS web site http://pds.nasa.gov/tools/nasa-view.shtml.
User tutorials on the details of MDIS data products and how to open and process them with ISIS and other software are available online at the PDS, at http://pds-imaging.jpl.nasa.gov/software/.
Archive
|
An archive consists of one or more data sets along with all the documentation and ancillary information needed to understand and use the data. An archive is a logical construct independent of the medium on which it is stored. |
Archive volume, archive volume set
|
A volume is a unit of medium on which data products are stored; for example, one DVD. An archive volume is a volume containing all or part of an archive; that is, data products plus documentation and ancillary files. When an archive spans multiple volumes, they are called an archive volume set. Usually the documentation and some ancillary files are repeated on each volume of the set, so that a single volume can be used alone. |
Calibrated Data Records (CDRs) |
Image data calibrated to radiance, or processed further to I/F or I/F corrected to i = 30¼, e = 0¼ (NAC or WAC). CODMAC level 4. |
Data Product
|
A labeled grouping of data resulting from a scientific observation, usually stored in one file. A product label identifies, describes, and defines the structure of the data. An example of a data product is a planetary image, a spectrum table, or a time series table. |
Data Set
|
An accumulation of data products. A data set together with supporting documentation and ancillary files is an archive. |
Derived Data Records (DDRs) |
Geometric data registered to non-map-projected image data and used for correction from I/F to I/F corrected to i = 30¼, e = 0¼ (NAC or WAC). CODMAC level 6. |
Experiment Data Records (EDRs) |
Non-map-projected raw data (NAC or WAC). CODMAC level 2. |
Map Projected Basemap Reduced Data Records (BDRs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5. |
(8-color) Map Projected Multispectral Reduced Data Records (MDRs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (WAC filters 1, 3-12). CODMAC level 5. |
(3-color) Map Projected Multispectral Reduced Data Records (MD3s) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (WAC filters 6, 7, and 9). CODMAC level 5. |
(5-Color) Map Projected Multispectral Reduced Data Records (MP5s) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (WAC filters 4, 6, 7, 9, and 12). CODMAC level 5. |
Map Projected High-incidence Angle Basemap Illuminated from the East Reduced Data Records (HIEs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5. |
Map Projected High-incidence Angle Basemap Illuminated from the West Reduced Data Records (HIWs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5. |
Map Projected Low-incidence Angle Basemap Reduced Data Records (LOIs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (NAC or WAC filter 7). CODMAC level 5. |
Map Projected Regional Targeted Mosaic Reduced Data Records (RTMs) |
Map-projected I/F, I/F corrected to i = 30¼, e = 0¼, and relevant DDR layers (NAC or WAC filters 1, 3-12). CODMAC level 5. |
Standard data product
|
A data product defined during the proposal and selection process and that is contractually promised by the PI as part of the investigation. Standard data products are generated in a predefined way, using well-understood procedures, and processed in ÒpipelineÓ fashion. |
Special data product |
A data product of special interest that may require subjective judgment to produce and may not be produced in a pipeline fashion. Special products are produced as resources permit. |
The keywords listed below appear in the example labels found in Appendices C Ð L.
PDS_VERSION_ID
The version number of the PDS standards document that is valid when a data product label is created. PDS3 is used for the MESSENGER Data products.
File format parameters
RECORD_TYPE
The record format of a file.
RECORD_BYTES
The number of bytes in a physical file record, including record terminators and separators.
FILE_RECORDS
The number of physical file records, including both label records and data records.
LABEL_REVISION_NOTE
Provides information regarding the revision status and authorship of a PDS label.
^IMAGE
The pointer to a full image object. This object contains all the sub-frames which correspond to a given observation. The sub-frames are arrayed in their respective positions corresponding to a full frame observation. The value contains the starting record position in the file.
General data description parameters
MISSION_NAME
Identifies the MESSENGER planetary mission.
INSTRUMENT_HOST_NAME
The full, unabbreviated name of the spacecraft.
DATA_SET_ID
Uniquely identifies the data sets available on the volume.
DATA_QUALITY_ID
A data quality index is used to encode figures-of-merit into one parameter that is included in the label of each CDR or DDR. The 16-byte data quality index is interpreted as follows:
Byte 0: Image source is CCD.
1 = Image source is test pattern as indicated by
MESS:SOURCE=1=Test pattern or
MESS:SOURCE=2=Inverted test pattern.
0 = Image source is CCD as indicated by MESS:SOURCE=0=CCD.
Byte 1: Valid exposure time.
1 = Exposure time in ms as indicated by MESS:EXPOSURE equals 0 ms (during cruise) or is less than or equal to 2 ms (orbit).
0 = Exposure time in ms as indicated by MESS:EXPOSURE is greater than or equal to minimum valid value.
Byte 2: Presence of an excessive number of pixels at or approaching saturation.
As saturation is approached responsivity decreases, and signal becomes nonlinear with brightness for small sources. Saturation can be exceeded for very bright or large sources once pixel antiblooming is overwhelmed. The raw 12-bit DN level indicative of the onset of saturation varies between the two CCDs. In the WAC (MESS:IMAGER=0) it is approximately 3600; in the NAC (MESS:IMAGER=1) it is approximately 3400. If a LUT has been used to convert 12-bit to 8-bit DN, then an 8-bit DN value of 255 also indicates saturation. An 8-bit 255 is encountered before saturation of the 12-bit DN in the case of LUT 1. In autoexposure mode, the typical threshold for the allowable number of saturated pixels is 5 pixels. In manual exposure mode the number of saturated pixels is uncontrolled.
1 = There are > 5 pixels exceeding the DN indicating onset of saturation.
0 = There are < 5 pixels exceeding the DN indicating onset of saturation.
Byte 3: Valid pivot position.
1 = Pivot position not valid, as indicated by pivot position validity flag MESS:PIV_PV=0=invalid
0 = Pivot position valid as indicated by both keywords having a value of 1=valid.
Byte 4: Filter wheel in position (WAC only; requires MESS:IMAGER=0, or else value of this byte = 0).
1 = Filter wheel not in position, as indicated by any of three conditions:
(a) filter wheel position validity flag MESS:FW_PV=0=invalid,
(b) filter wheel reading validity flag MESS:FW_RV=0=invalid, or
(c) an excessive difference between filter wheel resolver goal and actual position as given in table below.
0 = Filter wheel in position as indicated by an allowable difference between goal and position, and by both MESS:FW_PV=1 and MESS:FW_RV=1 (See Table B-1).
Table B-1: Filter wheel encoder positions
FILTER_NUMBER |
MESS:FW_GOAL |
Allowable (abs(MESS:FW_POS - MESS:FW_GOAL)) |
1 |
17376 |
+/- 500 |
2 |
11976 |
+/- 500 |
3 |
6492 |
+/- 500 |
4 |
1108 |
+/- 500 |
5 |
61104 |
+/- 500 |
6 |
55684 |
+/- 500 |
7 |
50148 |
+/- 500 |
8 |
44760 |
+/- 500 |
9 |
39256 |
+/- 500 |
10 |
33796 |
+/- 500 |
11 |
28252 |
+/- 500 |
12 |
22852 |
+/- 500 |
Byte 5: Quality of spacecraft attitude knowledge.
1 = Spacecraft attitude knowledge is bad (MESS:ATT_FLAG is in the range 0-3).
0 = Spacecraft attitude knowledge is good (MESS:ATT_FLAG is in the range 5-7).
Byte 6: CCD temperature range.
1 = CCD out of temperature range at which performance is well calibrated (MESS:CCD_TEMP is outside a range of between 1005 and 1130, which for the WAC is -45C to -11 C, and for the NAC is -48C to -14C).
0 = CCD within well calibrated temperature range (MESS:CCD_TEMP is within the stated range).
Byte 7: Completeness of data within the commanded selection of subframes or full frame.
Missing frames or portions of frames are indicated in an EDR with a value of 0 (this cannot be a valid data value).
1 = There are missing data (some pixels populated with 0).
0 = There are no missing data.
Bytes 8-15: spare.
PRODUCT_ID
The permanent, unique identifier assigned to a data product by its producer. In the PDS, the value assigned to product_id must be unique within its data set.
PRODUCT_TYPE
Identifies the type or category of a product within the data set.
PRODUCT_VERSION_ID
Identifies the version of an individual product within the data set.
SOURCE_PRODUCT_ID
This is a set of input files used as input to create this product. The first element is the original spacecraft solid state recorder (SSR) filename as downlinked. Additional elements are the SPICE kernels used to produce the ancillary data.
PRODUCER_INSTITUTION_NAME
The organization responsible for developing the data products.
SOFTWARE_NAME
The name of the software system that created the data products. The version number of the software is identified by the SOFTWARE_VERSION_ID keyword.
SOFTWARE_VERSION_ID
Version of the software used to generate the data products.