PDS_VERSION_ID = PDS3 RECORD_TYPE = STREAM OBJECT = TEXT NOTE = "Comments on the Viking Lander EDR image CD-ROMs" PUBLICATION_DATE = 1997-06-20 END_OBJECT = TEXT END COMMENTS ON VIKING LANDER EDR IMAGE CD-ROMS This document contains comments and errors concerning the Viking Lander EDR image archive published on CD-ROM. 1. Image File 11A053.N15 This image has the wrong PLANET_DAY_NUMBER (sol) in its label. The correct value should be 7. It is listed as 8 in the original VICAR label and published catalogs. 2. Image File 22F028.RED This image was missing from the original tape set that contained the EDR images. It is also missing from later generations of EDR tapes. Thus, this image cannot be recovered for inclusion in this archive. 3. Image Files 11A021.BLU, 11A021.GRN, and 11A021.RED Sections at the top and bottom of these images appear to be blank. The pixel values in these sections are either 0 or 4. 4. Image Files 12F219.BB1 and 11F220.N15 Image 11F220.N15 is a calibration frame acquired along with image 12F219.BB1. As such, the same camera acquired these two images. The original VICAR labels and published catalogs list image 12F219.BB1 as being acquired by camera 2 and image 11F220.N15 as being acquired by camera 1. Because both images should have the same camera, one of them is wrong. From the available documentation, the correct camera for these two images cannot be determined. 5. STOP_TIME Keyword in the PDS Labels and Image Index Files The value for the STOP_TIME keyword was computed using the scan rate and number of imaging lines. STOP_TIME was computed because only START_TIME is available in the original VICAR labels and published catalogs. According to Huck et al. (Space Science Instr., v. 1, p. 189-241, 1 975), 3414 bits were recorded for each imaging line. There were 3072 bits of image data acquired for each scan line and the remaining bits were engineering data. Using the value for bits per line quoted above yields reasonable STOP_TIME for images acquired early in the mission. However, the computed STOP_TIME for some images acquired later in the mission overlaps with the START_TIME of the next image. This implies that the number of bits of engineering data recorded with the image data changed during the mission. Thus, the STOP_TIME values should be viewed as being approximate. 6. START_TIME Keyword for Calibration Images A few calibration images have the same START_TIME as the image they were acquired with. The following is a list of calibration images that are known to have the same START_TIME as the image they were acquired after: 21I137, 21I140, 21I141, and 21I143. 7. DETECTOR_TEMPERATURE Keyword The DETECTOR_TEMPERATURE values in the PDS image label and index tables represent the average temperature of the camera photosensor array (PSA) during image acquisition. This temperature may be useful in doing advanced radiometric calibration. The DETECTOR_TEMPERATURE value was computed from the 6-bit DN value returned in the engineering data associated with the image. The DN value was stored in the original VICAR label of each image. Temperatures in degrees C were computed using an expression given in the final Viking Lander picture catalog document (NASA RP 1137): T = 2.089 * DN - 62.0 This equation can be inverted to compute the original DN value. Note that the first Viking Lander picture catalog document (NASA RP 1007) gave a slightly different equation for conversion from DN to temperature. Further, the final picture catalog document (NASA RP 1137) states that some of the temperature values in the VICAR labels are wrong. No other Viking Lander image documentation deals with PSA temperatures or explains these discrepancies. 8. Images with data from Another Camera Event A few images have imaging lines that were recorded during another camera event. This may have been caused by problems with the tape recorder on the spacecraft or during the ground processing. The following images have been visually identified to contain data from another camera event: 11E086.BB4, 12F157.RED, 21H076.BLU, 22H094.SUN, 21H165.BB3, 22H198.SUN, 22H199.SUN, and 21I080.BB1. 9. Camera Events Not Received on Earth Some camera events were commanded and acquired, but were not received on Earth due to communications problems. The original Lander EDR image tapes contained blank image files for camera events not received on Earth. Those blank image files have been omitted from this archive. The following is a list of camera events not received on Earth. Viking Lander 1 Viking Lander 2 12A015 22B084 11A020 22B097 12A082 21B110 12B204 21B215 12B205 21B150 11B214 21B189 12B215 21B218 11B216 21B237 11B217 22D090 11C209 22D221 11C214 22D222 11C215 21D236 11D003 22E141 11D058 22E217 12F159 22E218 12F183 22E223 12F186 21E228 11F252 21F107 11G001 21G057 11G051 22G060 11G052 21G187 11G053 21G188 11G054 22G189 11G055 21G213 11H007 21G214 11H008 21G215 11H234 22G216 11H235 22G244 12I208 22G245 12I209 22G246 12I210 22G247 12I211 22G248 11I212 22G255 12I213 22H226 12I214 21H227 12I215 22I002 12I216 21I003 11I217 22I112 12I218 22I113 12I219 22I114 12I220 22I115 12I221 22I120 12I222 12I223 12I224 12I225 11I226 12I227 12I228 12I229 12I230 12I231 12I232 12I233 12I234 12I235 12I236 12J018 12J019 11J020 11J021 11J022 12J023 12J024 11J025 11J026 11J027 11J030 11J031 11J032 11J033 12J034 11J035 11J037 12J038 12J039 11J040 11J041 11J042 12J043 11J045 11J051 12J054 12J059 11J061 11J065 12J073 12J074 12J083 11J086 11J087 12J088 11J090 11J091 11J092 12J094 11J095 11J096 12J098 12J099 11J101 12J104 11J105 11J106 12J109 11J112 12J114 11J116 11J117 12J118 12J119 11J121 11J126 12J128 11J131 11J132 12J133 12J134 11J135 11J137 12J138 12J139 12J143 12J144 11J146 12J148 11J151 11J152 12J159 11J165 11J167 11J177 11J187 12J188 11J191 11J192