CCSD3ZF0000100000001NJPL3IF0PDS200000001 = SFDU_LABEL RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 80 SPACECRAFT_NAME = MAGELLAN TARGET_NAME = VENUS OBJECT = TEXT PUBLICATION_DATE = 1992-01-17 NOTE = "COMMENTS ON MAGELLAN MIDR CD-ROMS" END_OBJECT END COMMENTS ON MAGELLAN MIDR CD-ROMS 1. Purpose of This Document This document is a cumulative summary of comments concerning the Magellan MIDR data set published on CD-ROMs. It contains comments on all the MIDR CD-ROMs published so far. Comments include information of interest to users of the data and notes about any known errors on the CD-ROMs. 2. General Comments 2.1 Normalization of Data Note that the eight-bit digital numbers (DN's) for each MIDR pixel on the CD-ROM's were computed by taking the estimated backscatter cross sections, dividing the values by the value for the Muhleman scattering law at the same incidence angles, converting to decibels, and scaling to bytes. The Muhleman Law has the following expression: sigma naught = A cos(i) / (sin(i) + B cos(i)) ** 3 Values for A and B were meant to be 0.0188 and 0.111, respectively Through an error, the A value used for the Muhleman Law estimate was 0.0118. As a result of this mistake, the pixel values are systematically about 10 DN (2 dB) greater than they should be according to the planned algorithm. Also, because of an indexing error, the incidence angles used in the above equation were 0.5 degrees lower than the actual angles. 2.2 VICAR2 Labels of Browse Images The browse versions of MIDRs were created by reducing the original 7168 by 8192 MIDR by a factor of 8. The VICAR2 labels for the browse images do not accurately reflect the size reduction, in that parameters PROJSAMP, PIXSIZ, and SPECLINE still pertain to the original MIDR size. 2.3 Data Feathering MIDR products on the CD-ROM's, in some cases, have had a feathering algorithm applied to suppress banding due to BIDR differences. The file CONTENTS.TAB includes a column (column no. 31) that specifies whether or not feathering has been applied. A "C" in this column indicates correction by feathering, while an "R" means not feathered. 3. Comments on volume MG_0001, version 2 3.1 Difference between MG_0001 file structure and Standard file structure The files MCUMDIR and CONTENTS are in the root directory of MG_0001. They are in subdirectory INDEX of MG_0002 and subsequent CD's. In addition, MG_0001 has a label file PMIDRDS.LBL in the LABEL directory. This file is replaced by NPMIDRDS.LBL and SPMIDRDS.LBL in the LABEL subdirectory of MG_0002 and subsequent CD's. For MG_0002 and subsequent CD's, a number of other label and text files (including AAREADME.TXT) have been updated to reflect these and a few other minor changes. 3.2 Difference between Standard and Engineering F-MIDRs The ten F-MIDRs on this CD-ROM are not standard products; rather, they are engineering test products generated before delivery of operational software. There are three primary differences between Engineering F-MIDRs and standard F-MIDRs. First, Engineering F-MIDRs consist of 20 orbits whereas standard F-MIDRs contain 24 orbits. Second, Engineering F-MIDRs are not necessarily complete on the trailing edge and may contain missing orbits within the body of the mosaic that have since been processed. The gap at the trailing edge of some of the F-MIDRs is a start of mapping gap and is present because processing began with orbit 376. Gaps in the bodies of the F-MIDRs are present because the Image Data Processing Team (IDPT) was instructed not to wait until all orbits had completed the processing queue. Therefore, orbits that the SAR Data Processing Team (SDPT) had trouble processing appear as gaps in the Engineering F-MIDRs even though the orbit has now been processed. 3.3 Error in VICAR2 Keyword PROJSAMP This CD-ROM has an error in the VICAR2 labels for the mosaic framelets. Specifically, the value for PROJSAMP does not vary from framelet to framelet. 3.4 VICAR2 Labels of MIDR Framelets Some of the MIDR framelet files have a VICAR2 label embedded at the end of the file, in addition to the normal VICAR2 label at the beginning of the file. This extra label is not documented in the PDS detached label. 3.5 Product ID in VICAR2 Label In two of the data subdirectories, the product ID given in the VICAR2 embedded labels is not correct. Specifically, the VICAR2 label has an N for north latitude instead of an S for south latitude. The correct IDs are as follows: directory product ID in VICAR2 labels correct product ID --------- --------------------------- ------------------ [F05S335] F-MIDR.05N335 F-MIDR.05S335 [F40S342] F-MIDR.40N342 F-MIDR.40S342 3.6 Error in BROWSE.LBL Files The PDS label files for the browse images on this CD-ROM (all named BROWSE.LBL) contain incorrect entries in the IMAGE object. The keyword LINES, which shows a value of 1024, should have the value 896. The keyword LINE_SAMPLES, which shows a value of 896, should have the value 1024. 4. Comments on Volume MG_0003, version 1 The F-MIDR products, F50S345, F55N337, F60N334, F65N330 and F75N332, on CD-ROM MG_0003 are the standard product replacements for five of the engineering test product F-MIDRD's on MG_0001. 5. Comments on GEO.LBL for Volumes MG_0001 to MG_0022 The PDS label file GEO.LBL on Magellan CD's volumes 1 to 22 contain incorrect DESCRIPTION keyword entries for the objects MINIMUM_LONGITUDE and MAXIMUM_LONGITUDE. The correct entries for these objects are: OBJECT = COLUMN NAME = MINIMUM_LONGITUDE DATA_TYPE = REAL UNIT = DEGREE START_BYTE = 19 BYTES = 8 DESCRIPTION = "The minimum_longitude element specifies the westernmost (left_most) longitude of the feature." END_OBJECT = COLUMN OBJECT = COLUMN NAME = MAXIMUM_LONGITUDE DATA_TYPE = REAL UNIT = DEGREE START_BYTE = 28 BYTES = 8 DESCRIPTION = "The maximum_longitude element specifies the easternmost (right_most) longitude of the feature." END_OBJECT = COLUMN Previously, the DESCRIPTION keyword for MINIMUM_LONGITUDE referred to "easternmost" and the DESCRIPTION keyword for MAXIMUM_LONGITUDE referred to "westernmost". 6. Comments on Volume MG_0012 Framelet 56 for C1-MIDR 60N014 has zeros in approximately 6.5 records starting at line 605 sample 513 and continuing to line 611 sample 1024. This will result in a horizontal black band across the framelet and may cause problems with some automated processing algorithms. 7. Comments on Volume MG_0014 Framelet 36 for C1-MIDR 00N009 has zeros in approximately 7 records starting at line 316 sample 513 and continuing to line 323 sample 512. This will result in a horizontal black band across the framelet and may cause problems with some automated processing algorithms. 8. Comments on Volume MG_0015 Framelet 22 for F-MIDR 20N097 has zeros in approximately 6 records starting at line 360 sample 513 and continuing to line 366 sample 512. This will result in a horizontal black band across the framelet and may cause problems with some automated processing algorithms. 9. Comments on Volumes MG_0023 to MG_0026 The PUBLICATION_DATE keyword in MCUMCOMM.TXT shows an incorrect date. The date is supposed to be 1991-10-03 not 1991-09-03. 10. Comments on Volume MG_0030 The file CONTENTS.TAB, in directory INDEX, shows 141 as the maximum longitude for product C1_75N119. The maximum longitude entry for this product should be 186. 11. Comments on Volume MG_0041 11.1 Comments on FRAME.TAB The file FRAME.TAB in directory C175N209 incorrectly reports the maximum longitude of framelet C1F02 to be 175.9575. This should be 183.4368. Also, FRAME.TAB reports the minimum longitude of framelet C1F03 to be 183.4495. The minimum longitude for framelet C1F03 is 175.9738. (Although locations are reported to four significant figures, spatial accuracy is actually much lower. 11.2 Comments on [C175N209]C1F02.LBL The MAXIMUM_LONGITUDE keyword in this file has a value of 175.9575. The value should be 183.4368. 11.3 Comments on [C175N209]C1F03.LBL The MINIMUM_LONGITUDE keyword in this file has a value of 183.4495. The value should be 175.9738. 11.4 Comments on CONTENTS.TAB The file CONTENTS.TAB, in directory INDEX, reports 186 as the minimum longitude for product C1_75N209. The minimum longitude entry for this product should be 142. 12. Comments on Volume MG_0043 The file CONTENTS.TAB, in subdirectory INDEX, reports the maximum latitude (northernmost), the minimum latitude (southernmost), the maximum longitude (easternmost) and the minimum longitude (westernmost). Since the product C2-MIDR 60N033 on this CD lies in the far northern hemisphere, the image wraps around itself. Consequently, the maximum longitude and minimum longitude entries in CONTENTS.TAB are not appropriate indications of the longitude limits for this image. These entries in CONTENTS.TAB have therefore been set to 0. This approach adheres to the file structure given in the MIDRCD SIS. The actual limits of product C2-MIDR 60N033 are: LATITUDE LONGITUDE Upper Left Corner 82.5 192.1 Lower Left Corner 36.7 0.0 Upper Right Corner 82.5 233.2 Lower Right Corner 36.7 65.3 13. Comments on GEO.TAB on all volumes GEO.TAB contains names and locations of specific features on Venus. The file is dynamic and contains a number of spelling and location errors. The file is periodically updated, but the user should be careful in using this data. Contact Raymond Batson if you have comments on GEO.TAB. Raymond Batson Branch of Astrogeology U.S. Geological Survey 2255 North Gemini Drive Flagstaff, Arizona 86001 (602) 556-7260 NASAmail: RAY.BATSON 14. Product Lists for Volumes MG_0001 to MG_0050 The following is a list of MIDR products, sorted by longitude then by latitude (from north pole to south pole). PRODUCT TYPE: FMIDRS PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCL F_25N003 7 1 F_45N126 17 1 F_05S211 29 1 F_40S279 49 1 F_20N003 7 1 F_15N129 15 1 F_10S211 29 1 F_20N280 46 1 F_20S003 6 1 F_30S129 13 1 F_45S211 28 1 F_45S280 49 1 F_25S003 6 1 F_35S130 13 1 F_30S212 28 1 F_60N281 45 1 F_30S003 6 1 F_25S131 13 1 F_15S214 29 1 F_30N281 42 1 F_35S003 6 1 F_40S131 18 1 F_10N217 32 1 F_35N283 44 1 F_45N004 7 1 F_60N132 18 1 F_05N217 29 1 F_15S283 46 1 F_40S004 6 1 F_10N132 17 1 F_00N217 27 1 F_25N284 42 1 F_60N005 8 1 F_05N132 17 1 F_05S217 28 1 F_10N284 45 1 F_60S005 5 1 F_00N132 17 1 F_45S218 29 1 F_05N284 45 1 F_65S005 5 1 F_05S132 15 1 F_20S221 29 1 F_00N284 49 1 F_65N006 8 1 F_10S132 15 1 F_05S222 32 1 F_10S284 46 1 F_70N007 7 1 F_30S136 15 1 F_40S222 29 1 F_40N286 46 1 F_25S009 7 1 F_40S138 13 1 F_25N223 32 1 F_20N286 46 1 F_30S009 7 1 F_45S142 38 1 F_20N227 32 1 F_20S286 39 1 F_50S013 18 1 F_20N145 17 1 F_10N228 38 1 F_40S286 49 1 F_15N014 11 1 F_20S145 18 1 F_05N228 32 1 F_30N287 44 1 F_10N014 10 1 F_40S145 18 1 F_25N229 32 1 F_15S289 46 1 F_55S014 18 1 F_50N147 26 1 F_40N230 35 1 F_35N290 36 1 F_60N016 7 1 F_55N152 23 1 F_35N230 35 1 F_05N290 46 1 F_60S016 8 1 F_10S155 23 1 F_40S230 32 1 F_10S290 46 1 F_65N018 7 1 F_20S156 23 1 F_20N233 36 1 F_35S290 49 1 F_40N018 7 1 F_25S156 23 1 F_20S233 35 1 F_55N291 49 1 F_45N019 11 1 F_15S157 23 1 F_10N234 32 1 F_20N292 44 1 F_45S019 18 1 F_30S161 23 1 F_55N236 36 1 F_30N294 50 1 F_15N020 11 1 F_65N162 26 1 F_75N237 36 1 F_45N295 49 1 F_10N020 8 1 F_20S162 24 1 F_30N237 38 1 F_05S295 50 1 F_50N021 8 1 F_25S162 23 1 F_15N237 35 1 F_70N296 49 1 F_50S021 39 1 F_15S163 23 1 F_15S237 35 1 F_25N296 50 1 F_30S022 10 1 F_35S163 23 1 F_20N239 35 1 F_25S296 50 1 F_55N023 8 1 F_60N164 26 1 F_05N239 36 1 F_50N297 49 1 F_40N025 8 1 F_50N172 27 1 F_05S239 35 1 F_35N297 50 1 F_60N026 8 1 F_10N177 24 1 F_45N241 38 1 F_40S300 50 1 F_50N054 13 1 F_05N177 23 1 F_15S243 38 1 F_10S301 50 1 F_55N060 11 1 F_05S177 24 1 F_35S243 35 1 F_70N310 50 1 F_10N065 13 1 F_10S177 24 1 F_40N244 42 1 F_60N312 50 1 F_05N065 9 1 F_15S180 25 1 F_40S244 35 1 F_65N330 1 1 F_00N065 9 1 F_20S180 26 1 F_10S245 39 1 F_65N330 3 1 F_05S065 10 1 F_05S183 26 1 F_20S245 39 1 F_75N332 1 1 F_10S065 10 1 F_10S183 26 1 F_50N247 39 1 F_75N332 3 1 F_05N070 9 1 F_65N186 27 1 F_25S247 39 1 F_30N332 1 1 F_00N070 9 1 F_25N186 26 1 F_45N249 39 1 F_60N334 3 1 F_05S070 9 1 F_20N186 25 1 F_15N249 36 1 F_60N334 1 1 F_10S070 9 1 F_15N186 32 1 F_15S249 38 1 F_20N334 1 1 F_40S074 18 1 F_10N188 25 1 F_05S250 36 1 F_05S335 1 1 F_05N076 8 1 F_05N188 24 1 F_10S250 39 1 F_55N337 1 1 F_00N076 9 1 F_10S188 25 1 F_40N251 44 1 F_55N337 3 1 F_05S076 9 1 F_00N189 24 1 F_20S251 39 1 F_70N339 4 1 F_10S076 9 1 F_15N191 25 1 F_25S253 42 1 F_27S339 1 1 F_35N077 11 1 F_20N192 24 1 F_15S254 38 1 F_15N340 3 1 F_45N080 11 1 F_40N194 28 1 F_30N256 38 1 F_65N342 4 1 F_20N080 15 1 F_10N194 24 1 F_20S257 38 1 F_40S342 1 1 F_05N082 10 1 F_05N194 24 1 F_25S259 42 1 F_60N344 4 1 F_00N082 10 1 F_00N194 24 1 F_15N260 36 1 F_25N345 4 1 F_05S082 8 1 F_45N195 26 1 F_15S260 38 1 F_25S345 3 1 F_10S082 9 1 F_50N197 27 1 F_30N262 36 1 F_50S345 3 1 F_25S082 13 1 F_35N197 27 1 F_30S262 42 1 F_50S345 1 1 F_35S083 11 1 F_15N197 25 1 F_55N263 42 1 F_55N346 4 1 F_05N087 10 1 F_65N198 28 1 F_50N264 42 1 F_40S349 4 1 F_00N087 10 1 F_20N198 25 1 F_15N266 45 1 F_45S349 3 1 F_05S087 10 1 F_10N200 25 1 F_10N267 45 1 F_75N351 7 1 F_10S087 10 1 F_05N200 25 1 F_10S267 36 1 F_25N351 4 1 F_40N088 11 1 F_00N200 25 1 F_30N269 44 1 F_20N351 4 1 F_50S088 11 1 F_10S200 27 1 F_20N269 44 1 F_70N353 6 1 F_35S090 11 1 F_15N203 35 1 F_30S269 42 1 F_65N354 6 1 F_20N097 15 1 F_20N204 28 1 F_60N270 42 1 F_65S354 3 1 F_10N098 17 1 F_20S204 29 1 F_35N270 44 1 F_60N355 6 1 F_05N098 15 1 F_50N205 28 1 F_40N272 44 1 F_55S355 4 1 F_05S098 15 1 F_10N205 32 1 F_50S272 39 1 F_60S355 3 1 F_10S098 15 1 F_05N205 27 1 F_10N273 45 1 F_50N356 6 1 F_65N102 15 1 F_00N205 27 1 F_05N273 45 1 F_50S356 4 1 F_60N111 18 1 F_05S205 28 1 F_10S273 45 1 F_25N357 6 1 F_15N111 13 1 F_30S205 26 1 F_30N275 44 1 F_20N357 5 1 F_65N114 17 1 F_60N207 28 1 F_30S275 45 1 F_05N357 5 1 F_45N119 17 1 F_60S207 26 1 F_35N277 44 1 F_00N357 5 1 F_25N119 17 1 F_55N208 28 1 F_25N278 50 1 F_05S357 5 1 F_20S121 17 1 F_20S210 29 1 F_40N279 45 1 F_20S357 5 1 F_30N123 13 1 F_45N211 27 1 F_10N279 49 1 F_25S357 5 1 F_15S123 18 1 F_25N211 27 1 F_00N279 46 1 F_30S357 5 1 F_65N126 13 1 F_10N211 29 1 F_05S279 46 1 F_35S357 5 1 PRODUCT TYPE: C1MIDRS PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCL C1_30N009 12 1 C1_60S097 22 1 C1_30N189 31 1 C1_00N266 41 1 C1_15N009 14 1 C1_30N099 20 1 C1_30S189 31 1 C1_15S266 41 1 C1_00N009 14 1 C1_30S099 20 1 C1_15N197 33 1 C1_30N279 43 1 C1_15S009 14 1 C1_15N112 20 1 C1_00N197 33 1 C1_30S279 41 1 C1_30S009 14 1 C1_00N112 19 1 C1_15S197 33 1 C1_15N283 43 1 C1_45N011 14 1 C1_15S112 20 1 C1_45N202 31 1 C1_00N283 43 1 C1_45S011 12 1 C1_45N117 21 1 C1_45S202 31 1 C1_15S283 41 1 C1_60N014 12 1 C1_30N117 21 1 C1_75S203 48 1 C1_45N286 47 1 C1_60S014 16 1 C1_30S117 21 1 C1_30N207 33 1 C1_45S286 43 1 C1_15N026 12 1 C1_45S117 21 1 C1_30S207 33 1 C1_60N291 47 1 C1_00N026 12 1 C1_75N119 30 1 C1_60N208 37 1 C1_60S291 47 1 C1_15S026 12 1 C1_60N125 21 1 C1_60S208 34 1 C1_75S293 48 1 C1_30N027 12 1 C1_60S125 22 1 C1_75N209 41 1 C1_30N297 47 1 C1_30S027 14 1 C1_15N129 20 1 C1_15N215 34 1 C1_30S297 43 1 C1_75N029 16 1 C1_00N129 19 1 C1_00N215 33 1 C1_75N299 48 1 C1_45N032 12 1 C1_15S129 19 1 C1_15S215 33 1 C1_15N300 47 1 C1_45S032 14 1 C1_30N135 30 1 C1_45N223 37 1 C1_00N300 47 1 C1_60N042 16 1 C1_30S135 21 1 C1_45S223 33 1 C1_15S300 47 1 C1_60S042 20 1 C1_45N138 21 1 C1_30N225 34 1 C1_45N307 47 1 C1_45N053 16 1 C1_45S138 21 1 C1_30S225 34 1 C1_30N315 48 1 C1_15N060 16 1 C1_15N146 22 1 C1_15N232 37 1 C1_30S315 47 1 C1_00N060 14 1 C1_00N146 22 1 C1_00N232 34 1 C1_15N317 48 1 C1_15S060 16 1 C1_15S146 22 1 C1_15S232 34 1 C1_00N317 48 1 C1_30N063 16 1 C1_60N153 31 1 C1_60N236 40 1 C1_15S317 48 1 C1_30S063 16 1 C1_30N153 22 1 C1_60S236 37 1 C1_60N319 48 1 C1_60N070 19 1 C1_30S153 22 1 C1_30N243 40 1 C1_45N329 47 1 C1_60S070 21 1 C1_60S153 22 1 C1_30S243 40 1 C1_30N333 2 1 C1_75N074 22 1 C1_45N159 30 1 C1_45N244 40 1 C1_30S333 2 1 C1_45N074 20 1 C1_45S159 22 1 C1_45S244 40 1 C1_15N335 2 1 C1_45S074 16 1 C1_15N163 31 1 C1_75S248 48 1 C1_00N335 2 1 C1_15N077 19 1 C1_00N163 31 1 C1_15N249 41 1 C1_15S335 2 1 C1_00N077 16 1 C1_15S163 30 1 C1_00N249 40 1 C1_75N338 14 1 C1_15S077 19 1 C1_75N164 37 1 C1_15S249 40 1 C1_60N347 14 1 C1_30N081 20 1 C1_30N171 31 1 C1_75N254 48 1 C1_60S347 31 1 C1_30S081 20 1 C1_30S171 31 1 C1_30N261 40 1 C1_45N350 12 1 C1_15N095 19 1 C1_60N180 30 1 C1_30S261 40 1 C1_45S350 2 1 C1_00N095 19 1 C1_45N180 30 1 C1_60N263 41 1 C1_30N351 12 1 C1_15S095 19 1 C1_15N180 30 1 C1_60S263 41 1 C1_30S351 2 1 C1_45N096 20 1 C1_00N180 30 1 C1_45N265 41 1 C1_15N352 2 1 C1_45S096 19 1 C1_15S180 30 1 C1_45S265 40 1 C1_00N352 2 1 C1_60N097 21 1 C1_60S180 33 1 C1_15N266 41 1 C1_15S352 2 1 PRODUCT TYPE: C2MIDRS PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCLE PRODUCT CD CYCL C2_30N026 34 1 C2_30N078 33 1 C2_30S129 37 1 C2_00N183 34 1 C2_30S026 37 1 C2_30S078 37 1 C2_00N131 34 1 C2_30N232 43 1 C2_00N028 37 1 C2_00N080 30 1 C2_30N181 43 1 C2_30S232 43 1 C2_60N033 43 1 C2_30N129 34 1 C2_30S181 37 1 C2_00N234 43 1