================================================================================ DIRBE TIME-ORDERED DATA (TOD) RECORD STRUCTURE Version: Pass 2B data release, Sept/Oct 1994 This file provides a condensed listing of the record structure for the DIRBE Time-Ordered Data (TOD). In several places of this abbreviated listing, fields of little or no value to the user have been combined into one field with a general description of its contents. The full listing can be made available upon request. Each record of TOD corresponds to a single major frame (MF) which lasts 32 sec. References to minor frames (mnfs) within this description follow the telemetry numbering scheme, i.e., minor frames are numbered 0 through 127. A single sampling of a detector's output is contained within a half minor frame (hmnf). There are 256 hmnfs within each major frame. =============================================================================== Column Headings: 'Offset' is the position of the first byte of a field relative to the start of the record. The count starts with byte 0. 'Length' refers to the total length, in (8-bit) bytes, of each data field. 'Description' indicates whether the field contains a scalar or an array of data, the type of data (and its dimension(s) if an array), and the name of the field. Further information is provided in comment lines beginning with "!". Example: The DIRBE science data is contained in field DADRBSCI2, which begins at byte 512. The science data is stored as a 2-D integer array (2-byte words) with dimensions of (16,256). Thus the total length of 8192 = 2 * 16 * 256 bytes. The fields most important for the user have been indicated by the notation: ******** KEY FIELD ******** "Late" fields (denoted by: --- LATE FIELD --- ) appear in major frame N+1 but apply to time frame covered in major frame N. All data apply to current major frame unless indicated as a late field. ================================================================================ RECORD DIRBE_TOD DIRBE_TOD /DURATION=00:00:32 Offset Length Description ------ ------ ----------- ! !--------Major frame header !This section defines the structure of !the DIRBE major frame Header. ! 0 14 SCALAR /TEXT/LEN=14 DATIMAS !GMT_ASCII spacecraft major frame start ! time ! Format: YYDDDHHMMSSttt ! The time of the middle of the first hmnf ! is the Major Frame time minus 0.3125 sec 14 8 SCALAR /ADT DATIMBI !Major frame start time in Vax Binary Format ! The time of the middle of the first hmnf ! is the Major Frame time minus 0.3125 sec 22 6 ARRAY /WORDU/DIM=3 DAPB5 !Major frame start time in PB5 Format ! The time of the middle of the first hmnf ! is the Major Frame time minus 0.3125 sec 28 4 SCALAR /LONGU DASCMJFN !Major frame number based on ! spacecraft clock time ! Reset daily 32 4 SCALAR /LONGU DASCORBN !Orbit Number ! Not currently used 36 1 SCALAR /BYTE TELEMETRY_FORMAT ! 1 - science format ! 2 - engineering format ! 3 - dump format ! -1 - indeterminate format 37 19 ARRAY /BYTE/DIM=19 INGEST_SPARES 56 8 ARRAY /BYTE/DIM=8 DAHDRSPR !Header Spares to bring header ! size up to standard size ! of 64 bytes 64 4 ARRAY /WORDU/DIM=2 DAYRDAY !Year & Day ! DAYRDAY(1) contains ! the day number ! DAYRDAY(2) contains ! the year number 68 4 ARRAY /BYTE/DIM=4 DATIME !Time ! Not currently used !----Spacecraft Position, Spacecraft Velocity !This section defines the structure of !DIRBE Major Frame attitude values. 72 8 SCALAR /DOUBLE DOUBLE_TIME !Double precision, Real*8 ! time. Matches field ! "DATIMBI" ! Units: 100 nanoseconds ! The time of the middle of the first hmnf ! is the Major Frame time minus 0.3125 sec 80 4 SCALAR /LONG EXT_INFLUENCES !External influence flags, set by ! facility BLI. One two-bit flag ! per detector, in process order, ! starting with the least significant ! bits, set according to the total ! number of glitches found in the ! major frame. ! ! 00 = Total number of glitches in ! the MF are within "normal" ! range. ! 01 = Total number of glitches in ! the MF exceed yellow limit, ! but not the red limit. ! 10 = Total number of glitches in ! the MF exceed red limit. ! 84 12 ARRAY /FLOAT/DIM=3 SC_POSITION !Spacecraft orbital position at the middle ! of major frame. Frame of ! reference is Geocentric Equatorial, ! 2000. ! Units: Meters ! Range: Determined by orbital ! parameters. 96 12 ARRAY /FLOAT/DIM=3 SC_VELOCITY !Spacecraft orbital velocity at the middle ! of major frame. Frame of ! reference is Geocentric Equatorial, ! 2000. ! Units: Meters/sec ! Range: Determined by orbital ! parameters. 108 128 ARRAY /FLOAT/DIM=(4,8) ATT_QUAT !******** KEY FIELD ******** !Attitude quaternions (best available ! solution at time of merging), ! 4 seconds intervals, starting at ! the Major Frame time minus 0.3125 s ! (the time of the middle of the ! first hmnf) 236 1 SCALAR /BYTE ATT_SOLN !Tells which solution was obtained ! from Attitude subsystem. !Possible values: ! CTOD_Fine_Aspect = 0 ! CTOD_Coarse_Aspect = 2 ! CTOD_Coarse_Non_Definitive = 3 237 1 SCALAR /BYTE NODE_FLAG !Flag representing the direction of ! motion of the spacecraft (not the ! field of view) with respect to ! the Ecliptic plane at the middle ! of major frame. ! 0 = Unknown ! 1 = Descending (from north pole to ! the south) ! 2 = Ascending (from south pole to ! the north) 238 7 ARRAY /BYTE/DIM=7 ATT_SPARES 245 8 SCALAR /DOUBLE T81_time !******** KEY FIELD ******** ! Major Frame start time in TAI seconds ! since 1-JAN-1981:00:00:00.000 UTC. ! The time of the middle of the first hmnf ! is the Major Frame time minus 0.3125 sec. 253 1 SCALAR /BYTE MERGE_FLAG !The first five bits of this ! flag represent the merge ! status of cross talk related ! data, attitude data, and orbit ! data into the major frame. !Bit 0 : when set, indicates that ! DMR data have been merged ! into the major frame. !Bit 1 : when set, indicates that ! FIRAS data have been merged ! into the major frame. !Bit 2 : when set, indicates that ! spacecraft data have been merged ! into the major frame. !Bit 3 : when set, indicates that ! orbit data (spacecraft and earth ! orbit) have been merged into ! the major frame. !Bit 4 : when set, indicates that ! attitude quaternions and ! angular velocities have ! been merged into the ! major frame. !Bits 5 - 7 : not used. 254 2 FILL /BYTES=2 !--------First Level Quality subsegment !This section defines the structure of !DIRBE Major Frame First Level Quality flags. 256 105 ARRAY /BYTE/DIM=105 DAQUALFLAGS !This contains flags signalling !various instrumental problems: !missing minor frames, saturated data, glitches, !chopper phase and amplitude problems, !microprocessor health, parity mismatches, !shutter and OMS problems. 361 151 ARRAY /BYTE/DIM=151 DAQUALX !Info for monitoring crosstalk from !other instruments and the spacecraft: !DMR noise diode data, !FIRAS temperatures and operating status. !Settings for or from torquer bars, gyros, !momentum wheels, reaction wheels, attitude !control electronics, sun sensor, !spacecraft buses, solar array, tape !recorders, and transponders !--------Science Words subsegment,linearized format. !This section defines the structure of !DIRBE Major frame science values (SDM mode)in !linearized format (non-SDM mode data are still !in the raw format). ! Science Words subsegment 512 8192 ARRAY /WORD/DIM=(16,256) DADRBSCI2 !******** KEY FIELD ******** ! The science words are formatted according to operating ! mode setting as follows. ! The field DAOMS identifies the DIRBE operation mode ! setting for each major frame. ! ! Mode Format ! ---------- -------------------------- ! 0=CTOD_SDM Compressed, IRS Calibrated, ! Celestial and Absolute calibrated, ! Linearized data. The data have ! been corrected for instrumental ! effects. Data for each detector are stored ! in the process order in which they were ! sampled by the MUX, not detector order. ! ! Units: MJy/sr ! ! Each datum is a floating-point ! value R, compressed into two bytes ! in the form: ! ! s n n n n x x x x x x x x x x x ! ! R = (s * x * 2**n) * M / f(b) ! ! BITS 0- 10: mantissa, the 10 MSB's of R ! BITS 11-14: exponent, power of two ! BIT 15 : sign bit (if set, ! value is negative) ! ! M = 0.5 / 16.0 / 27.12 = the smallest ! non-zero signal that can be ! detected (0.5) at maximum ! gain (16.0 * 27.12) ! ! Band, b Scale factor, f(b) ! --------- -------------------- ! 1a 3.0 ! 1b 2.4 ! 1c 1.9 ! 2a 2.6 ! 2b 0.86 ! 2c 0.74 ! 3a 3.2 ! 3b 1.1 ! 3c 0.90 ! 4 3.1 ! 5 0.88 ! 6 0.64 ! 7 0.20 ! 8 0.29 ! 9 0.013 ! 10 0.026 ! ! The errors introduced by this compression ! technique are no greater than the larger of: ! +/- 0.05% (1 sigma) ! or +/- 0.0006/f(b) MJy/sr ! ! Large negative values (sentinel values, ! R .LE. -16375.0) are stored directly as ! negative integers: ! WORD = R - 11985 ! ! ! Mode Format ! ---------- -------------------------- ! Bit mask name Function ! 1=CTOD_CAL ------------- -------- ! 2=CTOD_ETS CTOD_M_SDM_gainbit High/low gain flag: ! = '0001'X bit set => low gain ! amplifier was used and ! the DN may be recovered ! by dividing the data ! bits by ! 1.0 for all bands ! bit reset => high gain ! amplifier was used and ! the DN may be recovered ! by dividing the ! data bits by ! 15.78289,15.77305,15.7690, BAND 1a,b,c ! 15.88996,15.98606,15.97883, BAND 2a,b,c ! 15.7648, 16.00026,16.03776, BAND 3a,b,c ! 15.95889,15.79972,15.93593, BAND 4,5,6 ! 15.84680,15.9267, BAND 7,8 ! 15.83417,15.73266 BAND 9,10 ! CTOD_M_SDM_databits 12 bit reconstructed ! = 'FFFE'X analog/digital converter ! (ADC) value without ! high/low gain factor ! Mode Format ! ---------- -------------------------- ! 3=CTOD_ANL DADRBSCI2(I,J), CTOD_Firstchan=1 <= I <= ! CTOD_Lastchan=16; J even and ! CTOD_Firstmnf=0 <= (J-1)/2 <= ! CTOD_Lastmnf=127 ! ! Detector signal samples summed ! over minor frame (J-1)/2. The ! sum can be used to calculate ! the average DC value of the ! detectors. Note that the ! stored value is NOT the sum of ! the differences of each ! chopper cycle. ! ----------------------- ! CTOD_ANL_Firsthtr=1 <= I <= ! CTOD_ANL_Lasthtr=14; ! J odd and ! CTOD_Firstmnf=0 <= (J-1)/2 <= ! CTOD_Lastmnf=127 ! ! Commanded heater levels for ! detector I in minor frame (J-1)/2 ! ----------------------- ! CTOD_ANL_STDC_FLG_L=15 <= I <= ! CTOD_ANL_STDC_FLG_H=16; ! J odd and ! CTOD_Firstmnf=0 <= (J-1)/2 <= ! CTOD_Lastmnf=127 ! ! Short-term DC flags indicating at ! least one saturated ADC value was ! rejected when forming the average ! DC signal for the minor frame. ! Bit set => saturated value occurred ! Bit reset => no saturated value ! occurred ! ! Bits 0-7, word DADRBSCI2( CTOD_ANL_STDC_FLG_L=15, J) ! correspond to process numbers 1-8, respectively. ! ! Bits 0-7, word DADRBSCI2( CTOD_ANL_STDC_FLG_H=16, J) ! correspond to process numbers 9-16, respectively. ! ! ! ! Mode Format ! ---------- -------------------------- ! 4=CTOD_CBM DADRBSCI2(i,j) contains the continuous burst ! mode data sampled eight times ! per chopper cycle from either ! one channel or from two ! channels sampled alternately ! (sent in even and odd minor ! frames as specified in major ! frame words DACHASEL and ! DACHBSEL, resp.) There are 32 ! values per minor frame/channel ! ! Mode Format ! ---------- -------------------------- ! 5=CTOD_SNAP DADRBSCI2(I,J) CTOD_Firstchan=0 <= I <= ! CTOD_Lastchan=16; ! CTOD_Firstmnf=0 <= (J-1)/2 <= ! CTOD_Last_Snap_SDM=27 ! ! Science Data Mode formatted data for ! process number I-1 and collected ! during both halves of minor frame ! ((J+1)/2 - 1). Data in the first ! minor frame after the major frame ! boundary are filled with zeros. ! --------------------- ! ! CTOD_Firstchan=0 <= I <= ! CTOD_Lastchan=16 ! CTOD_First_snap_raw=28 <= (J-1)/2 <= ! CTOD_Lastmnf=127 ! ! Raw, unformatted ADC data for any two ! selected process numbers (sent in even and ! odd minor frames as specified in major ! frame words DAPRASEL and DAPRBSEL, ! respectively) covering the first 24 minor ! frames in the major frame. Data recorded ! for the first half minor frame are ! selected from process number A, and data ! from the second half minor frame are ! selected from process number B. ! Mode Format ! ---------- -------------------------- ! 6=CTOD_SNG DADRBSCI2(I,J) CTOD_Firstchan=1 <= I <= ! CTOD_Lastchan=16; ! CTOD_Firstmnf=0 <= (J-1)/2 <= ! CTOD_Lastmnf=127 ! ! Raw, unformatted ADC data for one ! selected channel (DACHASEL) covering ! the major frame. Each word contains ! raw ADC values sampled four times per ! chopper cycle (every 1/128 second). ! ! Mode Format ! ---------- -------------------------- ! 7=CTOD_STM STANDBY/MAINTENANCE MODE - NO SCIENCE DATA 8704 256 ARRAY /BYTEU/DIM=256 DASCPARITY !Parity of minor frames calculated !onboard and on the ground 8960 48 ARRAY /FLOAT/DIM=12 SS_POSITIONS !The positions of the sun, moon, Mars, !and Jupiter at start of the major frame. !Frame of reference is Geocentric !Ecliptic, 2000 !Units: meters, for sun ! AU, for moon, Mars, Jupiter 9008 96 ARRAY /FLOAT/DIM=(3,8) ANGULAR_VEL !COBE angular velocity vectors, ! 4 seconds apart, starting at the ! Major Frame time minus 0.3125 s ! (the time of the middle of the ! first hmnf), in instantaneous ! spacecraft body coordinates. 9104 12 ARRAY /BYTE/DIM=12 COORD_SPARES !----Processing flags !This section defines the structure of !DIRBE Major frame processing flag values. 9116 2 SCALAR /WORD DADOC ! BIT I, When set, indicates ! that detector offsets have not been ! subtracted for corresponding ! channel ( I=1 to 16) 9118 16 ARRAY /WORD/DIM=8 DACORRS !Corrections flags ! Array of flags indicating which ! corrections have been applied ! to the data. One word per ! type of correction, one bit ! per detector (starting with ! the least significant bit: ! bands 1a, 1b, 1c, 2a, 2b, ...) ! Word 1: GLC (temperature) ! Word 2: IRS Calibration ! Word 3: IRS/ANL induced gain ! Word 4: SAA induced gain ! Word 5: Photon Induced Respon- ! sivity Enhancement ! (hysteresis) ! Word 6: LTL (Light Transfer ! Linearization) ! Word 7: Cross-talk ! Word 8: External influences 9134 80 ARRAY /BYTE/DIM=80 CORR_MAX_BINS ! Not currently used 9214 1 FILL /BYTES=1 9215 1 SCALAR /BYTE DASPRC !Magnitude of spin rate change ! Not currently used !--------Internal SUBCOM subsegment !This section defines the structure of !DIRBE major frame subcommutated values, section 1. 9216 16 ARRAY /BYTE/DIM=16 DAANCNF ! --- LATE FIELD --- !Echo of Basic Gain setting command !Bit set -> on/closed unless otherwise stated ! Bit Field Meaning ! 0:2 Basic Gain setting of ! Analog Electronics ! 3 ETS command on/off ! 4 DC command on/off ! 1 = off (DC removed from signal) ! 0 = on (DC level put back into signal) ! 5 ETS select A/B ! 0 = A ! 1 = B 9232 32 ARRAY /BYTE/DIM=32 DAMEPS !******** KEY FIELD ******** ! --- LATE FIELD --- ! Within this field the ! bytes DAMEPS(2*N-1) and DAMEPS(2*N) ! (where N=1,2,3,...16) contain the ! high (x16) and low gain (x1) ! MUX entry port addresses ! for the Nth process sampled by the MUX. ! These addresses can be translated into ! detector numbers as follows: ! ! Detector High addr. Low addr. ! 1a 16 0 ! 2a 17 1 ! 3a 18 2 ! 1b 19 3 ! 2b 20 4 ! 3b 21 5 ! 1c 22 6 ! 2c 23 7 ! 3c 24 8 ! 4 25 9 ! 5 26 10 ! 6 27 11 ! 7 28 12 ! 8 29 13 ! 9 30 14 ! 10 31 15 ! ! E.g. For process N, if DAMEPS(2*N-1) = 16 and ! DAMEPS(2*N) = 0, then detector 1a is sampled. 9264 248 ARRAY /BYTEU/DIM=248 DASUBCOM1 ! Additional instrument settings and ! diagnostics. ! Radiation impacts, chopper mask position, ! sensor bias, annealing heater levels, ! long-term DC average of each detector, ! long-term average of out-of-phase amplitude ! of each detector. 9512 8 ARRAY /BYTEU/DIM=8 PCSV !******** KEY FIELD ******** ! The Pipeline Compressed State Vector ! Each byte contains several bit-encoded flags ! ! BYTE 1 CVT BASE FILE VERSION ! ! BYTE 2 EXTERNAL DATA QUALITY INDICATOR ! BITS 0-1 Fill data flag. ! 01 = missing some mnfs ! 11 = missing all ! BITS 2-3 Attitude control. ! Bit 2 set ==> spacecraft slewing ! Bit 3 set ==> Special (non-nominal) Pointing ! BITS 4-5 Definitive coarse/fine merged attitude Solution ! 11 = Coarse aspect (non-definitive) ! 10 = Coarse aspect (definitive) ! 00 = DIRBE fine aspect (definitive) ! BITS 6-7 SAA/Van Allen Belt Horn flags, ! based on a time 16 seconds ! after the MF time ! 00 = OK (or not checked, for ! backward compatibility) ! 01 = in the NVABH (Northern Van ! Allen Belt Horn) ! 10 = in the SVABH ! 11 = in the SAA ! ! BYTE 3 DATA AND MICROPROCESSOR ERRORS ! BYTE 4 RELAY STATUS ! BYTE 5 SIGNAL SOURCE ! BITS 0-1 Shutter state ! 01= shutter A open ! 10= shutter B open ! 11= both open ! BITS 2-3 ETS state ! 01= ETS on for some channels ! 10= ETS on for all channels ! BITS 4-5 IRS A state ! 01 = IRS A on for part of ! major frame ! 10 = IRS A on for whole ! major frame ! BITS 6-7 IRS B state ! 01 = IRS B on for part of ! major frame ! 10 = IRS B on for whole ! major frame ! ! BYTE 6 DEU CONFIGURATION ! BYTE 7 DETECTOR SETTINGS ! BYTE 8 SPARE 9520 2 SCALAR /WORD QUADRATURE ! Bitmask for detectors whose primary ! process has been replaced by the value ! obtained by combining all processes ! sampling the detector. (Two samples with ! 90 degree phase difference => quadrature) ! (In order 1A, 1B, 1C, 2A, ...) ! If quadrature was applied to detector ! 1A, then bit 0 = 1, although quadrature has ! no effect on bands that are not multiply ! sampled. ! Not relevant for cold-mission data. 9522 40 ARRAY /FLOAT/DIM=10 PHOTON_INTEGRAL ! Integrated photon exposure, calculated by ! adding the detector responses in ! linearized, IRS-calibrated DNs for all MFs ! preceding the current one, since last ! IRS-run. ! Calculated for SDM mode only, and ! only for the full-intensity bands ! (1A,2A,3A,4,5,6,7,8,9,10). 9562 17 FILL /BYTES=17 9579 36 ARRAY /BYTE/DIM=36 ATAMAG !Magnetometer readings ! Units : counts !--------Internal SUBCOM subsegment !This section defines the structure of !DIRBE major frame subcommutation values, section 2. 9615 8 ARRAY /BYTEU/DIM=8 DASUBCOM2A ! Misc. instrument flags/settings: ! onboard software version, commanded bits, ! test pluse, RAM errors, operating mode ! status 9623 1 SCALAR /BYTEU DAOMS !******** KEY FIELD ******** !Operating mode for the major frame ! Possible Values: ! 0 = CTOD_SDM - Normal Science Data mode ! 1 = CTOD_CAL - IRS calibration mode ! 2 = CTOD_ETS - ETS calibration mode ! 3 = CTOD_ANL - anneal detectors mode ! 4 = CTOD_CBM - continuous burst mode ! 5 = CTOD_SNAP- snapshot mode ! 6 = CTOD_SNG - single channel mode ! 7 = CTOD_STM - standby/maintenance mode 9624 176 ARRAY /BYTEU/DIM=176 DASUBCOM2B_3A !Flags for bad instrument commands, RAM, data ! mismatches, etc. Tally of commands recieved ! and of commands executed, and number of ! major frames. Checksums. ! Saturation flag and deglitcher ! setting (on/off). Internal Power ! Distribution Unit (IPDU) ! input/output voltages and currents, ! and temperatures 9800 16 ARRAY /BYTE/DIM=16 DAGRTID !DAGRTID(I) is the number of the ! germanium resistance thermometer ! (GRT) whose value is stored in ! DAGRT(I). ! Range: [CTOD_FirstGRT=0, ! CTOD_LastGRT=15] 9816 32 ARRAY /WORD/DIM=16 DAGRT !DAGRT(I) = Analog Value from GRT ! sensor number DAGRTID(I). ! 9848 376 ARRAY /BYTEU/DIM=376 DASUBCOM3B !Chopper phase, IRS volatges and settings, !relay status, thermistor data, !internal converter voltages !Various IRS/ETS mode flags and settings 10224 16 ARRAY /BYTEU/DIM=16 CEL_CAL_FLAGS !Bit encoded flags, in detector order ! (1A,1B,1C,2A,2B,...,10), indicating ! application of celestial calibration ! by BPC ! ! Bit 1: 0 = No celestial calibration Gain ! Coefficient has been applied ! (regardless of settings of ! other flags) ! 1 = GC has been applied ! Bit 2: 0 = no interpolation of GCs ! 1 = linear interpolation of GCs ! Bit 3: spare (hook for additional GC ! interpolation methods) ! Bit 4: spare (hook for additional GC ! interpolation methods) ! Bit 5: spare (hook for application of ! offset corrections) ! Bit 6: spare ! Bit 7: spare ! Bit 8: spare ! 10240 END_RECORD TOTAL LENGTH OF RECORD: 10240 BYTES