Mars Exploration Rover (MER) MERA (Spirit) and MERB (Opportunity) Data Archive Archive Contents Files in this archive are organized into a series of subdirectories below the top-level directory. The archive organization and the contents of each directory are described below. 1. AAREADME.TXT The file you are currently reading. 2. INDEX.TAB Text file in ASCII format that contains a list of MER ORR and DEM products. 3. DATA Directory The DATA direcotry contains data products from both MERA (Spirit) and MERB (Opportunity). 3.1. mera directory This directory contains stereo anaglphy RDR products from mera (Spirit). A stereo anaglyph is a method of displaying stereo imagery quickly and conveniently using conventional display technology (no special hardware) and red/blue glasses. This is done by displaying the left eye of the stereo pair in the red channel, and displaying the right eye in the green and blue channels. An anaglyph data product simply captures that into a single 3-band color image, which can be displayed using any standard image display program with no knowledge that it is a stereo image. The red (first) band contains the left eye image, while the green and blue (second and third) bands each contain the right eye image (so the right image is duplicated in the file). 3.2. merb directory The merb directory contains sub directories calibration, DEM, ORR, MI-relative-height, and true-attitude-products from merb (Opportunity). 3.2.1 calibration directory The calibration directory contains various reports documenting different aspects of instrument behavior. 3.2.2 DEM directory The DEM directory contains digital elevation map (DEM). This product is generated in orthographic projection as a single-banded mosaic image. Each pixel is an elevation height (Z), and the corresponding X and Y coordinates can be calculated from parameters in the image labels. 3.2.3 ORR directory The ORR directory contains orthorectified projection mosaic. The orthorectified projection mosaic is similar to the orthographic projection mosaic, except that a DEM of the type described in section 2.2 is used to remove elevation distortions. 3.2.4 MI-relative-height directory The MI-relative-height directory contains relative height products generated from images taken by the microscopic imager (MI) on the robotic arm. The relative height product is a single-banded image. Each pixel is an elevation height (Z), which is measured from the RAT grind plane. The corresponding X and Y coordinates can be calculated from parameters in the image labels. 3.2.5 true-attitude-products The true-attitude-products directory contains XYZ, surface normal, slope, mesh, and anaglyph products. The XYZ, surface normal, slope, and mesh products were generated using the true attitude information (quaternion/euler angle) calculated from the Nadir Check products. Please see the following paper for more information about Nadir Check: K.S. Ali, et al., Attitude and Position Estimation on the Mars Exploration Rovers, IEEE International Conference on Systems, Man and Cybernetics, 2005. 3.2.5.1 XYZ RDR products An XYZ file contains 3 bands of 32-bit floating point numbers in the Band Sequential order. XYZ locations in all coordinate frames for MER are expressed in meters unless otherwise noted. The pixels in an XYZ image are coordinates in 3-D space of the corresponding pixel in the reference image. This reference image is traditionally the left image of a stereo pair, but could be the right image for special products. The geometry of the XYZ image is the same as the geometry of the reference image. This means that for any pixel in the reference image the 3-D position of the viewed point can be obtained from the same pixel location in the XYZ image. The 3-D points can be referenced to any of the MER coordinate systems (specified by DERIVED_IMAGE_PARAMS Group in the PDS label). Most XYZ images will contain "holes", or pixels for which no XYZ value exists. These are caused by many factors such as differences in overlap and correlation failures. Holes are indicated by X, Y, and Z all having the same specific value. This value is defined by the MISSING_CONSTANT keyword in the IMAGE object. For the XYZ RDR, this value is (0.0,0.0,0.0), meaning that all three bands must be zero (if only one or two bands are zero, that does not indicate missing data). 3.2.5.2 Surface Normal RDR products A Surface Normal (UVW) file contains 3 bands of 32-bit floating point numbers in the Band Sequential order. The pixels in a UVW image correspond to the pixels in an XYZ file, with the same image geometry. However, the pixels are interpreted as a unit vector representing the normal to the surface at the point represented by the pixel. U contains the X component of the vector, V the Y component, and W the Z component. The vector is defined to point out of the surface (e.g. upwards for a flat ground). The unit vector can be referenced to any of the MER coordinate systems (specified by the DERIVED_IMAGE_PARAMS Group in the PDS label). Most UVW images will contain "holes", or pixels for which no UVW value exists. These are caused by many factors such as differences in overlap, correlation failures, and insufficient neighbors to compute a surface normal. Holes are indicated by U, V, and W all having the same specific value. Unlike XYZ, (0,0,0) is an invalid value for a UVW file, since they're defined to be unit vectors. Thus there's no issue with the MISSING_CONSTANT as there is with XYZ, where (0.0,0.0,0.0) is valid. 3.2.5.3 Slope RDR products The Slope Map RDR represents the predicted slope of the terrain as determined by Pancam and Navcam stereo imaging. The Slope Map is derived from the XYZ product by fitting a plane over a rover- sized patch in physical space for every image plane pixel in the Pancam and Navcam stereo images. The surface normal is then computed as the normal to the plane fit. Note that the surface normal used for Slope is not the same as the UVW product. While it uses fundamentally the same algorithm, the UVW product is based on a RAT-sized patch and is intended for use with IDD operations, while the surface normal used in slope calculations (which is not archived) is based on a rover-sized patch. Finally, the elevation of the surface normal vector with respect to the (X,Y) site frame is determined to be the predicted terrain slope in units of degrees. 3.2.5.4 Terrain mesh RDR products Terrain models are a high level product which are derived from the XYZ files and the corresponding image files. The terrain models are generated by meshing or triangulating the XYZ data based on the connectivity implied by the pixel ordering or by a volume based surface extraction. The XYZ files can be viewed as a collection of point data while the terrain models take this point data and connect it into a polygonal surface representation. The original image is referenced by the terrain models as a texture map which is used to modulate the surface color of the mesh. In this way the terrain models can be viewed as a surface reconstruction of the ground near the instrument with the mesh data capturing the shape of the surface and the original image, applied as a texture map, capturing the brightness variations of the surface. 3.2.5.5 Anaglyph RDR products A stereo anaglyph is a method of displaying stereo imagery quickly and conveniently using conventional display technology (no special hardware) and red/blue glasses. This is done by displaying the left eye of the stereo pair in the red channel, and displaying the right eye in the green and blue channels. An anaglyph data product simply captures that into a single 3-band color image, which can be displayed using any standard image display program with no knowledge that it is a stereo image. The red (first) band contains the left eye image, while the green and blue (second and third) bands each contain the right eye image (so the right image is duplicated in the file). 4. DOCUMENT The DOCUMENT directory contains documentation to help the user understand and use the archive data. 5. SOFTWARE The SOFTWARE directory contains a python script named OrthoMosaic.py. This script is a "wrapper" of VICAR program marsortho, and it is capable of generating the ORRs and DEMs in the DATA directory. In order to use the script, the following conditions must be met: 1. VICAR software must be installed and its environment must be properly configured. 2. MER OSS directory structures should exist. The script assumes MER OSS directory structures to read input images and write output images. 6. Whom to Contact for Information For questions concerning this volume, contact: PDS Imaging Node Jet Propulsion Laboratory 4800 Oak Grove Dr. Pasadena, CA 91109 (818) 354-5677 WWW Site: http://pds-imaging.jpl.nasa.gov E-mail: amy.c.chen@jpl.nasa.gov deborah.l.padgett@jpl.nasa.gov you.lu@jpl.nasa.gov For general information related to the PDS, contact: Planetary Data System, PDS Operator Jet Propulsion Laboratory 4800 Oak Grove Drive Pasadena, CA 91109-8099 (818) 354-4321 WWW Site: http://pds.jpl.nasa.gov/ E-mail: pds_operator@jpl.nasa.gov