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NJPL1I00PDS000000000 FILE_TYPE = TEXT RECORD_TYPE = STREAM END EEliason/USGS/Flagstaff, Az. 1987/Mar/01 VOYAGER IMAGE FILE ORGANIZATION ------------------------------- INTRODUCTION ------------ This compact read-only disc (CDROM) contains digital images acquired by the Voyager 1 and 2 spacecraft. The image collection contains scenes of the planets Jupiter and Saturn, including images of their rings and satellites. The image data are raw; no radiometric, geometric, or data clean-up procedures have been applied to the images. Digital images and their associated supplementary information are organized as direct-access files with fixed-length records. Image files are made up of three components; a label section, an image array, and a trailer section. The label section contains ASCII keyword entries which describe file attributes, camera conditions, target, time of observation, and other parameters. The image array contains the image data and supplemental line information. The trailer section contains supplemental engineering data. The disc volume and directory structure conforms to level-1 of the NISO Standard for Read-Only Optical Media (formerly the High-Sierra format). CDROM Volume and Directory Structure ------------------------------------------ The volume and directory structure on this CDROM conforms to the proposed American National Standard for Information Sciences--Volume and File Structure of CDROM for Information Interchange as of August 27, 1986. This standard is informally known as the High-Sierra format. This disc conforms to level-1 of the High-Sierra. For computer operating systems which support the High-Sierra standard, access to the CDROM volume will be simple; all of the operating system capabilites which handle files and directories will work on the disc. Thus, directory listings and file copy functions can be performed, and high-level language input/output system-interface routines can be utilized. For computer systems which do not support the High-Sierra standard, access to the image files will be more difficult; special operating system input/output routines will need to be developed in order to access the files. For more information on the NISO volume and directory structure, consult the document shown below: "Proposed American National Standard for Information Sciences-- Volume and File Structure of CDROM for Information Interchange", Document DL 87-47, Developed in coordination with the National Information Standards Organization, National Bureau of Standards, Administration 101, Library E-106, Gaithersburg, MD 20899 IMAGE FILES AND DIRECTORY STRUCTURE ----------------------------------- Each digital image and its associated supplementary information (image identification, location, and characteristics) are stored in a single file. The name of the file is constructed from the clock count of Voyager's Flight Data Sub-system (FDS) at the time the image was acquired. The FDS count is a unique identification associated with an image frame. The general form of an image file name is Cxxxxxxx.IMG. The character "C" at the begining of the file name designates the xxxxxxx as a clock count. The xxxxxxx is the seven digit FDS count associated with the image frame. The .IMG file extension specifies the file as an uncompressed image file. IMAGE FILE ORGANIZATION ----------------------- The image files conform to NASA's Planetary Data System (PDS) format guidelines for the archival of digital planetary images. PDS image files are organized as direct-access files containing contiguously positioned fixed-length records. This organization was adopted to provide file access for programs written in a wide variety of high-level languages. Many high-level input/output routines support direct-access with fixed-length records. For computer operating systems which support the High-Sierra volume and directory standard, programmers will not need to develop their own low-level routines for accessing the files. In addition, direct-access files allow any part of a file to be accessed directly without the need to sequentially pass through a file. PDS image files are a subset of a multi-dimensional file structure being defined by PDS. Direct-access files with fixed-length records have implied records; there is no information in the file designating the start or end of a record. Rather, the first byte of a record within a file starts at a fixed offset byte position from the start of the file. To determine the record byte-offset position, the following calculation can be made: OFF = (REC-1)*LEN where: OFF = offset byte of record from start of file REC = desired record to access (REC=1,2,3,...805) LEN = length of record in bytes A PDS image file is divided into three areas: a label area found at the start of file, an image area immediately following the label area, and a trailer area found at the end of the file. Each of these areas is constructed from an integral number of fixed-length records. The label area is constructed in an ASCII keyword format and contains information defining file characteristics, identifying the image frame, defining the state of the camera, and other parameters. The image section consists of line records; each fixed-length record in this area contains an image scan-line and its line engineering data. The trailer section contains detailed supplemental engineering data for the image frame. Voyager image files on this CDROM volume contain records of length 836 bytes with 805 records in the file. Records 1 and 2 contain the label area; records 3 through 802, for a total of 800 records, contain the image area; and records 803 through 805 contain the trailer area. IMAGE LABEL AREA AND KEYWORD ENTRIES ------------------------------------ The first two fixed-length records in an image file contain the keyword label area with information about the file organization, image identification, image target, and camera instrument characteristics at the time the image frame was recorded. The two records, when concatenated together, consist of a contiguous string of 1672 ASCII characters which can be extracted and typed to a terminal or printed in normal fashion. The label area contains a series of keyword entries of the form; parameter_name = value /* comment The keyword label area conforms to the PDS label standard as of January 1, 1987. The PDS label standard was considered preliminary at this time, and subject to future changes. For a detailed description of the PDS syntactic rules, consult the PDS Labels Standards Document. A brief description of the image label syntactic rules is given in Appendix 1. An example of the keyword entries for a Voyager image file follows; a description of each keyword entry is provided in Appendix 2. Keyword entries found on an image file -------------------------------------- NJPL1I00PDS000672960 = PDS_SFDU_LABEL /* FILE CHARACTERISTICS FILE_TYPE = IMAGE RECORD_TYPE = FIXED_LENGTH RECORD_BYTES = 836 FILE_RECORDS = 805 LABEL_RECORDS = 2 IMAGE_RECORDS = 800 TRAILER_RECORDS = 3 /* IMAGE ARRAY CHARACTERISTICS IMAGE_LINES = 800 LINE_SAMPLES = 800 LINE_SUFFIX_BYTES = 36 SAMPLE_BITS = 8 SAMPLE_BIT_MASK = 2#11111111# /* IMAGE DESCRIPTION SPACECRAFT_NAME = VOYAGER_2 MISSION_PHASE = URANUS_ENCOUNTER TARGET_BODY = MIRANDA FRAME_ID = '1699U2-001' SPACECRAFT_CLOCK_COUNT = 26846.11 /*FLIGHT DATA SUBSYSTEM SPACECRAFT_EVENT_TIME = 1986/01/24-16:39:09 <UTC> EARTH_RECEIVED_TIME = 1986/01/25-22:18:04 <UTC> INSTRUMENT_NAME = NARROW_ANGLE_CAMERA INSTRUMENT_SCAN_RATE = '1:1' INSTRUMENT_SHUTTER_MODE = NAONLY INSTRUMENT_GAIN_STATE = LOW INSTRUMENT_EDIT_MODE = '1:1' /*FULL RESOLUTION INSTRUMENT_FILTER_NAME = CLEAR INSTRUMENT_FILTER_NUMBER = 0 INSTRUMENT_EXPOSURE_DURATION = 1.92000 <SECONDS> END IMAGE AREA ----------- The image area is located in records 3 through 802 for a total of 800 records. Each record in this area is a line record consisting of an image scan-line and the engineering data for the scan-line. The IMAGE_RECORDS keyword in the label defines the total number of records in the image area, always 800 for Voyager frames. The IMAGE_LINES keyword, also 800, indicates the total number of scan-lines in the image array. The IMAGE_RECORDS and the IMAGE_LINES keywords are required in PDS labels because there may be multiple records per image line for other instruments. The LINE_SAMPLES keyword, always 800, indicates the number of samples in a single line of the image array. Byte positions 1 through 800 of a record contain the image line data. The LINE_SUFFIX_BYTES keyword, always 36, specifies the number of bytes of engineering data which follows the image line data. The line engineering data is located in byte positions 801 through 836. A description of the line engineering data can be found in Appendix 3. IMAGE TRAILER AREA ------------------ The image trailer area is located in records 803 through 805 for a total of 3 records. The 3 records, when concatentated together, consist of a contiguous string of 2508 bytes. The data in the trailer contains supplemental engineering data which typically will not be used by most image processing users. Information in this area includes the image histogram, FDS counts at start and end of image acquisition, system noise levels, synchronization error counts, engineering status, subcommand loads, and other engineering information. A description of the image trailer area can be found in Appendix 4. APPENDIX 1 ---------- SYNTACTIC RULES OF KEYWORD ENTRIES IN LABEL AREA ------------------------------------------------ The first two fixed-length records of an image file contain the label area. These two records, when concatentated together, consist of a continuous string of 1672 ASCII characters. The label area contains a series of keyword entries containing the names of parameters and their associated values. Each keyword entry is contained on a line separated from the next keyword entry by an ASCII carriage-return control character followed by a line-feed character. The keyword entries terminate with a line that contains only the keyword END. The remaining label area, after the END keyword entry, is padded with ASCII space characters. A keyword/value entry contains the name of one parameter and the value of that parameter. A keyword entry has the general form; parameter_name = value /* comment The layout of each keyword entry is essentially free-form; blanks and tabs are typically ignored by a parsing routine. A keyword parameter name is separated from the keyword value by the equal symbol (=). Each keyword entry may optionally be followed by a comment that more completely describes the entry. The comment begins with a slash character followed by an asterisk character (/*), and terminates with the end of the line on which it appears. Comments may exist on a line without a keyword entry. Values associated with a keyword name contain ASCII characters which represent integers, real numbers, unitized real numbers, literals, time, or character text strings. INTEGER NUMBERS --------------- An integer value consists of a string of decimal digits preceded optionally by a sign (+ or -). Non-decimal based integers are expressed according to the ADA language convention: b#nnnnnnn#, where 'b' represents the base of the number, and '#' delimits the number 'nnnnnnnn'. As an example, the number expressed as 2#111# represents the binary number 111 (7 in base 10). REAL NUMBERS ------------ A real number has the form: [s]f.d[En] where: s = optional sign (+ or -) f = one or more decimal digits that specify the integral portion of the number. d = one or more decimal digits that specify the fraction portion of the number. n = an optional exponent expressed as a power of 10. A unitized real number is a real number with a unit of measurement associated with the number. The units are enclosed in angle brackets (< >). As an example, 1.234 <SECONDS> indicates the measurement 1.234 seconds. TIME ---- A special form of a numeric field is the TIME value, the following format of date/time representation is used: yyyy/mm/dd-hh:mm:ss.fff <units> where: yyyy = year mm = month dd = day of month hh = hour mm = minute ss = seconds fff = fraction of seconds <units> = unit of time, example <UTC> for universal time corrected LITERAL VALUES --------------- A literal value is typically a member of a set of finite values. It is a string constructed from letters (A-Z), decimal digits (0-9), and the underscore character (_). The first character must be a letter. Optionally, a literal value may be delimited by single-quote (') characters. If a literal appears within single-quotes, the literal may contain any printable ASCII character. For example, the literal value '1:1' is legal as long as the single-quoted format is used. By example, the keyword/value entry of INSTRUMENT_FILTER_NAME = BLUE contains the literal value BLUE. There are a finite number of filter wheel positions of the camera, and the BLUE position is one of the positions. TEXT CHARACTER STRINGS ----------------------- Text strings can be any length and can consist of any sequence of printable ASCII characters, tabs, blanks, carriage-control, or line-feed characters enclosed in double-quote characters. A String continues until a double-quote character is encountered. APPENDIX 2 ---------- KEYWORD PARAMETERS FOR VOYAGER IMAGES ------------------------------------- NJPL1I00PDS000672960 = PDS_SFDU_LABEL This keyword provides a mechanism for PDS image files to conform to the SFDU (Standard Format Data Unit) convention. The first 20 bytes of a file are to contain a SFUD. The SFDU label associated with a PDS image file consists of the control authority identifier (characters 1-4), the version identifier (character 5), the class identifier (character 6), a spare field (characters 7-8), a format identifier (characters 9-12), and a length field indicator (characters 13-20). The keyword conforms to standard PDS keyword syntax and the value associated with this keyword will always be PDS_SFDU_LABEL. FILE_TYPE = IMAGE Defines the file type. For image files on this volume the value associated with the keyword will always be IMAGE. RECORD_TYPE = FIXED_LENGTH Defines the organization of records within the file. For image files on this volume, the records will always be fixed-length records. RECORD_BYTES = 836 Defines the number of bytes contained in a record, always 836 bytes. FILE_RECORDS = 805 Defines the total number of records contained in the file, always 805 records. LABEL_RECORDS = 2 Defines the number of records in the label area of the image file, always 2 records. IMAGE_RECORDS = 800 Defines the number of records in the image area of the file, always 800 records. TRAILER_RECORDS = 3 Defines the number of records in the trailer area of the file, always 3 records. IMAGE_LINES = 800 Defines the number of lines in an image, always 800. The first image line in the file is the top line of an image. LINE_SAMPLES = 800 Defines the number of samples contained in an image line, always 800. There are no prefix bytes in an image line and the first byte of an image record is the first sample (left-most sample) of an image line. LINE_SUFFIX_BYTES = 36 Defines the number of suffix bytes in an image line, always 36 bytes. The line suffix bytes contain supplementary line engineering data described in Appendix 3. SAMPLE_BITS = 8 Defines the number of bits per sample, always 8-bits per sample. The byte is an unsigned integer in the range 0 to 255. The 0 value indicates a null data value, and the 255 value indicates the sample is saturated. SAMPLE_BIT_MASK = 2#11111111# or 2#11111110# Defines the active bits of an image sample. The number is expressed as a base 2 value in the ADA language number base convention. The value for this keyword consists of a string of 1's and 0's. The value 1 indicates a bit is active and a 0 indicates a bit is not in use. For example, SAMPLE_BIT_MASK = 2#11111110# would indicate all bits are active except for the least significant bit and all samples should be an even number. The SAMPLE_BIT_MASK is dependent on the state of the camera. SPACECRAFT_NAME = VOYAGER_x Defines the spacecraft associated with the image, either VOYAGER_1 or VOYAGER_2. MISSION_PHASE = xxxxxxxxxxx Defines the central body of the mission encounter for this image. This literal value is either JUPITER_ENCOUNTER or SATURN_ENCOUNTER. TARGET_BODY = xxxxxx Defines the target body of the image. Literal value will contain the name of the planet, satellite or eithe J_RINGS or S_RINGS for ring system images. FRAME_ID = 'NNNNES+DDD' Defines the unique frame identification. For image data the value associated with this keyword is the picture identification. For Voyager data, it is of the form: NNNNES+DDD, where NNNN = picture sequence number for a given day, E = planet of encounter (J=Jupiter, S=Saturn, U=Uranus), S = the voyager spacecraft (1 or 2), a - sign indicates before and a + sign indicates after closest planetary approach. DDD = number of days from closest approach. SPACECRAFT_CLOCK_COUNT = xxxxx.xx Flight Data Subsystem (FDS) clock count at time of frame aquisition. The clock count is always a seven digit value, 5 digits to left of the decimal point and 2 digits to the right of the decimal point. SPACECRAFT_EVENT_TIME = yyyy/mm/dd-hh:mm:ss <UTC> Time at which image was aquired, the time system is Universal Time Corrected. yyyy=year, mm=month, dd=day of month, hh=hour, mm=minute, ss=second EARTH_RECEIVED_TIME = yyyy/mm/dd-hh:mm:ss <UTC> Time at which image was received on earth. INSTRUMENT_NAME = NARROW_ANGLE_CAMERA or WIDE_ANGLE_CAMERA Defines the instrument which acquired the data. For image data, the keyword value contains the camera used to acquire the data. Literal value will contain NARROW_ANGLE_CAMERA or WIDE_ANGLE_CAMERA. INSTRUMENT_SCAN_RATE = 'n:1' Scan rate of vidicon read out, values can be '1:1', '2:1', '3:1', '5:1', and '10:1'. The instrument scan rate effects the radiometric properties of the camera and effects the dark current build up on the vidicon. INSTRUMENT_SHUTTER_MODE = xxxxxx Literal value defining instrument shutter mode. Permitted values are; NAONLY - narrow angle camera shuttered only WAONLY - wide angle camera shuttered only BOTSIM - both cameras shuttered simultaneously BSIMAN - BOTSIM mode followed by NAONLY BODARK - shutter remained closed for narrow and wide angle camera NADARK - narrow angle read out without shuttering WADARK - wide angle read out without shuttering INSTRUMENT_GAIN_STATE = LOW or HIGH Literal value expressing the gain state of the camera. The gain state can be HIGH or LOW. INSTRUMENT_EDIT_MODE = xxxx Literal value expressing the edit mode of the camera. This keyword indicates amount of data read from the vidicon. '1:1' indicates the full resolution of the vidicon. Other values include '3:4', '1:2', '1:3', 1:5', and '1:10' INSTRUMENT_FILTER_NAME = xxxxxx Literal value expressing the optical filter used in the image frame. For Voyager images, permitted values are CLEAR, CH4_U, CH4_JS, UV, VIOLET, BLUE, GREEN, ORANGE, and NAD. INSTRUMENT_FILTER_NUMBER = x Optical filter identification number. This value contains the unique number associated with the optical filter used in the image frame. INSTRUMENT_EXPOSURE_DURATION = x.xxxxx <SECONDS> Unitized real number expressing the exposure duration of frame in seconds. DATA_ANOMALIES = xxxxxxxxxx Defines any data recording anomalies in the image frame. If this keyword is missing, no anomalies were detected. DATA_ANOMALIES = RAM_DATA_CORRUPTION indicates that spurious values exist in the image data due to corruption of the random access memory onboard the spacecraft. END The keyword entries terminate with a line that contains only the word END. Bytes in the label area after the END line are ignored. APPENDIX 3 ---------- SUPPLEMENTAL LINE ENGINEERING DATA ---------------------------------- The table shown below describes the information contained in an image line record. The supplemental line engineering data is found in byte positions 801 through 836 of the record. All integer values are stored in "least significant byte first" order. This is the order for integer values used by VAX and IBM PC computer systems. Users of other computer architectures (IBM Mainframes, Macintosh, Sun, and Apollo) will need to swap the high and low byte positions for 16-bit integer data. For 32-bit integer data, swap byte pairs 1 and 4, and 2 and 3. (Example, hex value AA BB CC DD becomes DD CC BB AA) BYTE DATA POSITION TYPE DATA DESCRIPTION --------------------------------------------------- 1-800 BYTE - Image scan line data 801-802 INTEGER*2 - FDS clock count, Mod 16 count 803-804 INTEGER*2 - FDS clock count, Mod 60 count 805-806 INTEGER*2 - FDS Mod line count 807-808 INTEGER*2 - Image line number 809-810 INTEGER*2 - Number of missing minor frames not present in line 811-830 INTEGER*2 - Number of telemetry frame bits retained for processing 831 BYTE - Bits 0-7 indentify input type as follows: 0 - S/C flight 2 data MOS 1 - S/C flight 1 data MOS 2 - PTM data 3 - Not used 4 - Extermanl simulation (SC41) 5 - Extermanl simulation (SC42) 6 - S/C flight 2 data test 7 - S/C flight 1 data test 832 BYTE - Input Source/Input type, bits 1-7 shown below 0 - Not used 1 - R/T data 2 - SDR tape data 3 - IDR tape data 4 - EDR (reprocessed data) 5 - Not used 6 - Not used 7 - fill data 833-834 INTEGER*2 - First valid pixel ID, element position (1-800) of the first pixel in this line not artificially set to zeros by MIPL processing. 835-836 INTEGER*2 - Element position of the last pixel in this line not artificially set to zeros by MIPL processing. APPENDIX 4 ---------- SUPPLEMENTAL ENGINEERING DATA IN TRAILER AREA ---------------------------------------------- The table shown below describes the information contained in the trailer area of an image file. The trailer area is found in records 803-805. The three records, when concatenated together, consist of a continuous string of 2508 bytes. All integer values are stored in "least significant byte first" order. This is the order for integer values used by VAX and IBM PC computer systems. Users of other computer architectures (IBM Mainframes, Macintosh, Sun, and Apollo) will need to swap the high and low byte positions for 16-bit integer data. For 32-bit integer data, swap byte pairs 1 and 4, and 2 and 3. (Example, hex value AA BB CC DD becomes DD CC BB AA) BYTE ITEM POSITION DATA DESCRIPTION -------- ------------------- ---------------------------------- 7-12 Earth Received Time Time of first line record of the file containing valid data. Bytes 7, 8 - year (7 bits), day of year (9 bits) Bytes 9,10 - minute (11 bits) Bytes 11,12 - milliseconds 13-18 Earth Received Time Time of last line record of the file containing valid data. (see format above) 19-24 FDS Count Count of the first line record of the file containing valid data. Note that this may not correspond to the FDS Count for line record #1. 25-30 FDS Count Count of the last line record of the file containing valid data. 31-36 Spacecraft Event Time Four binary fields corresponding to the (predicted) shutter-close time for this image. (see format for earth received time above) 37-68 IPL Physical IPL Data for first line record of Recording Data file (ASCII text). 69-88 GCF Data GCF for the first line record of the file containing valid data. Bytes 69-70 - GCF sync code (MSB) Byte 71 - GCF sync code (LSB) Byte 72 - Source code Byte 73 - Destination code Byte 74 - Block format code Bytes 75-76 - GDD(3-bits),UDT code (7-bits), DDT code (6-bits) Bytes 77-78 - Spacecraft number (7-bits) time (MSB) Byte 79-80 - time (LSB) Bytes 81-82 - Unused (2-bits), day of year (12-bits), block serial number MSB (2 bits) Byte 83 - LSB of block serial number Byte 84 - Millisecond clock Byte 85 - Serial number Byte 86 - GCF configuration status Bytes 87-88 - Unused (13-bits), esc (2-bits) Unused (1 bit). 89-108 GCF Data GCF for of the last line record of the file containing valid data. (see format above) 109-114 Internal Four binary fields representing Received Time approximate time of data receipt from the DACS: year of century = byte 109 day of year = byte 110 minute of day = bytes 111,112 millisecs in minute = bytes 113,114 115-118 Unused Unused 119-120 Format ID Telemetry format ID for this image. bytes 119-120 represent a word with Bits 8-15 = unused Bits 6-7 = format (=2 for imaging) Bits 1-5 = image format code. Note that the code used by the GDS may differ from the code down-linked by the spacecraft: 0=I3G4 12=IM2c 24=IM15 2=IMS 15=GS4 26=IM6 4=IMO 17=GS2 27=IM5 6=IMG 18=IM14 28=IM4 8=IMK 20=IM12 29=IM3 9=IM7 21=IM11 30=IM2 11=IM9 22=IM10 31=IM13 Bit 0 = S/C ID (0=VGR-2, 1=VGR-1) 121-122 System Noise The minimum noise level found for Temperature (Min) the scan-lines 123-124 System Noise The maximum noise level found for Temperature (Max) the scan-lines 125-126 Symbol SNR (Min) Minimum signal/noise ratio found for the scan-lines 127-128 Symbol SNR (Max) Maximum signal/noise ratio found for the scan-lines 129-130 AGC (Min) The minimum automatic gain control value used for the scan-lines 131-132 AGC (Max) The maximum automatic gain control value used for the scan-lines 133-134 Sync Code Errors Sum of the line sync. code errors for the scan lines 135-136 FDS Count Errors The sum of the FDS count errors for the scan lines which contain valid data 137-138 Sync Parameters Bits 8-15 contain the sync parameter I as described in the MTIS SRD. Bits 0-7 contain the sync parameter P as described in the MTIS SRD. 139-140 Sync Parameters 3 five-bit values representing the sync parameters J, K, and L as described in the MTIS SDR. J = bits 10-14 (bit 15=zero) K = bits 5-9 L = bits 0-4 141-142 Sync Parameters 3 five-bit values representing the sync parameters M, N, and R as described in the MTIS SDR. M = bits 10-14 (bit 15=zero) N = bits 5-9 R = bits 0-4 143-144 Number of Lines Total number of line records in the file which contain some valid data. 145-146 Number of Full Lines Number of line records in the file which are composed entirely of full minor frames. 147-148 Number of Partial Total number of line records in the Lines file which contain some valid data but are not composed entirely of full minor frames. 149-150 Number of Unreadable Total number of records from the IDR Records and/or SDR which were unreadable and which fell within a time period for which data was required for this file. Note: For SDR input this does not necessarily result in data loss. 151-152 Number of Logical Total number of gaps on the IDR Breaks and/or SDR as indicated by a discontinuity in the logical record numbers which fell within a time period for which data was required for this file. 153-154 Sort Parameters TBD catalog information. Will include target info from PIG file. 161-162 Number of Minor Total number of minor frames in this Frames from IDR file which were derived from IDR input. 163-164 Number of Minor Total number of minor frames in this Frames from WBDL file derived from WBDL input. 165-166 Number of Minor Total number of minor frames in this Frames from SDR file which were derived from SDR input. 167-168 Number of Missing Total number of frames which were Minor Frames missing from this file. 169-170 Not Used 171-179 Pic. No. Ten ASCII characters of the form: NNNNES+DD, where: NNNN = picture number within day. E = planet of encounter (J=Jupiter, S=Saturn,....) - = indicates before closest planetary approach + = indicates after closest planetary approach. DDD = Number of days from closest approach. 181-189 Target Body Ten ASCII characters (e.g. MIRANDA). 191-192 Input Source/Input Logical sum (result of successive Type inclusive or operations) of word 95 of all line records in the file. ISS STATUS/ENGINEERING SUBCOM DATA ---------------------------------- 193-194 Shuttered Picture Subcom position 1: Indicator Bit 15 = Camera ID (O=WA, 1=NA) Bits 0-14 = shuttered picture indicator = all ones for a shuttered image = zeroes for unshuttered images. 195-196 Slow Scan Status Subcom position 2: Bits 15-6 = Actual picture line number being read out. Bits 5-0 = Actual segment number being read out. Note: the slow scan status is meaningless here since it increments with line count. 197-198 Exp. Mode/Time/ Subcom position 3: Filter/Elec. Cal Bits 11-15 = spares Bit 10 = NA electronics cal status (1=on, 0=off) Bit 9 = WA electronics cal status (1=on, 0=off) Bits 4-8 = 5-bit exposure code. To convert to exp time, see MJS 77-4-2036. Bits 0-3 = Filter wheel position. Bits 1-3 give the position and Bit 0 is an odd parity bit. 199-200 Picture Count Subcom position 4. 201-202 Parameter A Word Subcom position 5. Present Value 203-204 Parameter A Word Subcom position 6. Indicator 205-206 Parameter A Word Subcom position 7. Pointer 207-208 Parameter B Word Subcom position 8. Present Value 209-210 Parameter B Word Subcom position 9. Pointer 211-212 Parameter C word Subcom position 10. Present Value 213-214 Parameter C word Subcom position 11. Pointer 215-216 Parameter D word Subcom position 12. Present Value 217-218 Parameter D word Subcom position 13. Indicator 219-220 Parameter D Word Subcom position 14. Pointer 221-220 Ten 8-bit Analogue Subcom positions 15-19. Samples 231-232 Pixel Average/ Subcom position 20. Command Status Bits 14-15 = spares Bits 13 = Pixel Average Status Bits 8-12 = Pixel Average is based on the MSBs of all pixels exceeding the programmed threshold of the camera read-out in the previous frame. For data compression formats (IMO, IMQ, IMK, and IM2c) this field is replaced by Command Status Word SC06QT: Bits 15-3 = unused Bit 2 = WA LSB Truncation FLag (0=truncation) Bit 1 = NA LSB Truncation Flag (0=truncation) Bit 0 = Secondary Memory Readout (1=readout) 233-242 ISS Engineering 9 ISS engineering measurements from ETAP. 243-1024 Unused Unused 1025-2048 Source data 256 32-bit binary valued histogram Histogram of the Histogram pixels for this file, including fill data. 2049-2508 Unused Unsused