FITS Headers
DIRBE_DCAF_P3B_FACE4.FITS
Primary Header
SIMPLE = T / file does conform to FITS standard BITPIX = 32 / number of bits per data pixel NAXIS = 0 / number of data axes EXTEND = T / FITS dataset may contain extensions COMMENT FITS (Flexible Image Transport System) format defined in Astronomy and COMMENT Astrophysics Supplement Series v44/p363, v44/p371, v73/p359, v73/p365. COMMENT Contact the NASA Science Office of Standards and Technology for the COMMENT FITS Definition document #100 and other FITS information. DATE = '09/04/97' / FITS file creation date (dd/mm/yy) DATE-MAP= '04/04/96' / Date of original file creation (dd/mm/yy) ORIGIN = 'CDAC ' / Cosmology Data Analysis Center TELESCOP= 'COBE ' / Cosmic Background Explorer satellite INSTRUME= 'DIRBE ' / COBE instrument [DIRBE, DMR, FIRAS] OBJECT = 'FACE4 ' / part of sky given [e.g., ALL-SKY, WEEKLY-SKY, COMMENT / DAILY-SKY, GAL-SLICE, FACE ...] EQUINOX = 2000.0 / equinox of coords in following tables REFERENC= 'COBE/DIRBE Explanatory Supplement,' / REFERENC= 'ed. M.G. Hauser, T. Kelsall, D. Leisawitz, and J. Weiland,' / REFERENC= 'COBE Ref. Pub. No. 97-A (Greenbelt,MD: NASA/GSFC),' / REFERENC= 'available in electronic form from the NSSDC.' / COMMENT COMMENT COBE specific keywords DATE-BEG= '11/12/89' / date of initial data represented (dd/mm/yy) DATE-END= '21/09/90' / date of final data represented (dd/mm/yy) PIXRESOL= 9 / Quad tree pixel resolution [6, 9] COMMENT COMMENT DIRBE specific keywords PRODUCT = 'DCAF_F4 ' / DIRBE Calibrated Annual File, Face 4 VERSION = 'Pass 3B ' / Version of Data Reduction Software WAVE1 = '1.25 microns' / nominal wavelength of Band 1 WAVE2 = '2.2 microns' / nominal wavelength of Band 2 WAVE3 = '3.5 microns' / nominal wavelength of Band 3 WAVE4 = '4.9 microns' / nominal wavelength of Band 4 WAVE5 = '12. microns' / nominal wavelength of Band 5 WAVE6 = '25. microns' / nominal wavelength of Band 6 WAVE7 = '60. microns' / nominal wavelength of Band 7 WAVE8 = '100. microns' / nominal wavelength of Band 8 WAVE9 = '140. microns' / nominal wavelength of Band 9 WAVE10 = '240. microns' / nominal wavelength of Band 10 SOLELONG= 'ALL ' / all available solar elongations included APPVEC = 'COMBINED' / data having different approach vectors COMMENT / are combined during processing ZLREMOV = F / zodiacal foreground removal indicator COMMENT / if 'T(rue)', zodi foreground has been removed COMMENT / if 'F(alse)', observed sky brightness is given COMMENT COMMENT END
Extension Header 2
XTENSION= 'BINTABLE' / Extension type is Binary Table BITPIX = 8 / Binary data NAXIS = 2 / Data are in a table NAXIS1 = 131 / Number of 8 bit bytes in each row NAXIS2 = 1079388 / Number of rows PCOUNT = 0 / Number of bytes of data following table GCOUNT = 1 / Group count (always 1 for bintable extensions) TFIELDS = 15 / Number of fields (columns) in the table COMMENT COMMENT TIMVERSN= 'OGIP/93-003' / GSFC Office of Guest Investigator Programs COMMENT / (OGIP) memo in which the convention is COMMENT / described COMMENT The times reported in this file are International COMMENT Atomic Time (TAI) seconds elapsed since COMMENT 00:00:00 UTC, 1 January 1981. Time information is COMMENT recorded in a manner consistent with the convention specified COMMENT in OGIP/93-003 with the understanding that time is counted COMMENT in atomic seconds and the origin of time (MJDREF) is quoted COMMENT in ephemeris MJD. TIMESYS = '1981.00 ' / time system (same as IRAS) MJDREFI = 44605 / Integer portion of ephemeris MJD COMMENT / corresponding to 0h UTC 1 Jan 1981 MJDREFF = 0.00059240741 / Fractional portion of ephemeris MJD COMMENT / corresponding to 0h UTC 1 Jan 1981 TIMEUNIT= 's ' / unit for TSTART, TSTOP, TIMEZERO = seconds TSTART = 282185275.611 / observation start time in TIMESYS system TSTOP = 306753235.358 / observation stop time in TIMESYS system COMMENT COMMENT COMMENT ------------------------------------------------------------------- COMMENT ******************************************************************* COMMENT ------ DIRBE Calibrated Annual File: Face 4 ----- COMMENT --------------- Cryogenic Mission --------------- COMMENT COMMENT The DIRBE Calibrated Annual File (DCAF) combines the COMMENT information contained in the 41 DIRBE Weekly Sky Maps COMMENT into a merged all-sky version which is sorted by ascending COMMENT DIRBE pixel number (resolution 9). Although the COMMENT information is identical to that given in the complete COMMENT set of Weekly Sky Maps for the cryogenic mission, the COMMENT data are organized differently, allowing more convenient COMMENT access to the full range of temporal variations observed COMMENT for each pixel. The DCAF table contains multiple row COMMENT entries for each pixel, one row for each mission week for COMMENT which photometric data are available. The multiple entries COMMENT per pixel are stored in consecutive rows which are COMMENT sorted in order of increasing observation time. COMMENT A companion Pixel Index is provided to facilitate data COMMENT selection and extraction. COMMENT COMMENT Because of its relatively large size, the DCAF has been COMMENT divided into six separate data files, each of which has COMMENT its own Pixel Index. Each of the six data files COMMENT corresponds to a face on the DIRBE skycube, and each is COMMENT named according to the face number. The face number COMMENT is also recorded in the OBJECT and PRODUCT keywords. COMMENT There is no overlap in sky coverage between the files. COMMENT Sky coverage is as follows: COMMENT COMMENT Range(*) of Range(*) of COMMENT Face No. DIRBE Pixel No.s Ecl. Longitude Ecl. Latitude COMMENT -------- ---------------- -------------- ------------- COMMENT 0 0 - 65535 0 - 360 deg +45 to +90 deg COMMENT 1 65536 - 131071 315 - 45 -45 to +45 COMMENT 2 131072 - 196607 45 - 135 -45 to +45 COMMENT 3 196608 - 262143 135 - 225 -45 to +45 COMMENT 4 262144 - 327679 225 - 315 -45 to +45 COMMENT 5 327680 - 393215 0 - 360 -45 to -90 COMMENT COMMENT (*) The ecliptic coordinate ranges are only approximate. COMMENT A more complete description of the sky coverage for each COMMENT face is provided in the DIRBE Explanatory Supplement, COMMENT Chapter 5. COMMENT COMMENT As with the DIRBE Weekly Sky Maps, the as-observed sky COMMENT brightness is tabulated; the foreground signal from COMMENT Zodiacal dust has not been removed. COMMENT ******************************************************************* COMMENT -------------------------------------------------------------------- COMMENT ==================================================================== COMMENT Coordinate Information (Spatial and Temporal): COMMENT ==================================================================== COMMENT -------------------------------------------------------------------- COMMENT DIRBE Pixel number (resolution 9) TTYPE1 = 'Pixel_no' / pipeline fieldname = Pixel_no TUNIT1 = ' ' / TFORM1 = '1J ' / COMMENT ------------------------------------------------------------------- COMMENT Sub-pixel containing the mean DIRBE LOS (line-of-sight) COMMENT when pixel is divided into 256 COMMENT sub-pixels (16x16 grid) according to COMMENT standard quad-sphere rules TTYPE2 = 'PSubPos ' / pipeline fieldname = Pixel_subpos TUNIT2 = ' ' / TFORM2 = '1B ' / COMMENT -------------------------------------------------------------------- COMMENT Sub-pixel number of the average line-of-sight COMMENT for individual bands which are expected to COMMENT have the largest offsets from the nominal position. COMMENT Subpixels are specified as a 16x16 grid COMMENT according to standard quad-sphere rules. COMMENT Byte 1: Sub-pixel for Band 1A COMMENT Byte 2: Sub-pixel for Band 4 COMMENT Byte 3: Sub-pixel for Band 7 COMMENT Byte 4: Sub-pixel for Band 8 TTYPE3 = 'Displace' / pipeline fieldname = Displacement_Means TUNIT3 = ' ' / TFORM3 = '4B ' / TDIM3 = '(4) ' / COMMENT -------------------------------------------------------------------- COMMENT Time in International Atomic Time (TAI) seconds COMMENT elapsed since 01-JAN-1981:00:00:00.000 UTC. COMMENT This is the average time of all observations of a pixel COMMENT within the time interval TSTART to TSTOP, COMMENT regardless of the weight assigned to a particular observation. TTYPE4 = 'Time ' / pipeline fieldname = Time TUNIT4 = 's ' / TFORM4 = '1D ' / COMMENT -------------------------------------------------------------------- COMMENT Difference between the average time of observation of the pixel COMMENT for each photometric band, and the COMMENT average time of all observations of the pixel (as given in the COMMENT TIME field). Therefore, for each pixel: COMMENT Average time of observation of Band x = TIME + (DeltaT for Band x). COMMENT Given in the order: 1A,2A,3A,4,5,6,7,8,9,10. COMMENT Range = [-7.0,+7.0) days TTYPE5 = 'DeltaT ' / pipeline fieldname = Delta_times TUNIT5 = 's ' / TFORM5 = '10B ' / TDIM5 = '(10) ' / TSCAL5 = 4725.0 / bin size (7*24*60*60)/(2**7) seconds TZERO5 = -602437.5 / offset to bin center in secs for unsigned byte COMMENT -------------------------------------------------------------------- COMMENT Mean solar elongation of observation, i.e. COMMENT angle between the vector from the spacecraft to the center COMMENT of the Sun and the DIRBE line-of-sight, COMMENT averaged over all observations of the pixel. COMMENT Nominal range = [64,124] degrees TTYPE6 = 'SolElong' / pipeline fieldname = Elongation TUNIT6 = 'deg ' / TFORM6 = '1I ' / TSCAL6 = 0.0109867 / bin size 360/(2**15 -1) degrees TZERO6 = 0.00549333 / offset to bin center in degrees COMMENT -------------------------------------------------------------------- COMMENT ==================================================================== COMMENT DIRBE Sky Brightness and Polarization Information: COMMENT ==================================================================== COMMENT -------------------------------------------------------------------- COMMENT Robust average of the week's photometric measurements COMMENT for the bands in the following order: COMMENT 1A,2A,3A,4,5,6,7,8,9,10. The photometric measurements COMMENT are given as spectral intensities, I(nu) in MJy/sr, and COMMENT are quoted at the nominal wavelength COMMENT for a source with nu*I(nu) = constant -- i.e., COMMENT a color correction is required if the source COMMENT spectrum differs from nu*I(nu) = constant. COMMENT Data which have been replaced by flagged values COMMENT in processing have values .LE. -16375. TTYPE7 = 'Photomet' / pipeline fieldname = Photometry TUNIT7 = 'MJy/sr ' / TFORM7 = '10E ' / TDIM7 = '(10) ' / COMMENT -------------------------------------------------------------------- COMMENT Stokes parameters Q and U for Band 1, Q and U COMMENT for Band 2, and Q and U for Band 3. COMMENT Range = (-2.0,2.0) COMMENT Nominal range = (-1.0,1.0) COMMENT Three possible cases arise in COMMENT storing the Stokes parameters for each band. COMMENT Bits 5 and 6 of the Polarization_quality_flag COMMENT field (StokQual) indicate which case applies: COMMENT Case 1: COMMENT Stokes parameters were calculated for the B and C COMMENT channels and the averages over both channels are COMMENT stored. COMMENT Case 2: COMMENT Stokes parameters were calculated for the B channel only. COMMENT Case 3: COMMENT Stokes parameters were calculated for the C channel only. COMMENT COMMENT Indeterminate quantities are set to a flagged value .LE. -16375. COMMENT TTYPE8 = 'Stokes ' / pipeline fieldname = Polarization TUNIT8 = ' ' / TFORM8 = '6E ' / TDIM8 = '(6) ' / COMMENT -------------------------------------------------------------------- COMMENT Number of observations of the pixel for this week COMMENT that contained at least one valid photometric measurement. TTYPE9 = 'NumRecs ' / pipeline fieldname = Num_recs TUNIT9 = ' ' / TFORM9 = '1I ' / COMMENT -------------------------------------------------------------------- COMMENT Number of observations which survived robust averaging COMMENT and quality constraints to form the photometric averages COMMENT supplied for each band in the 'Photomet' field. COMMENT Given in the order: 1A,2A,3A,4,5,6,7,8,9,10. TTYPE10 = 'WtNumObs' / pipeline fieldname = Weighted_num_obs TUNIT10 = ' ' / TFORM10 = '10B ' / TDIM10 = '(10) ' / TSCAL10 = 0.50 / bin size 0.5 TZERO10 = 0.0 / COMMENT -------------------------------------------------------------------- COMMENT Standard deviation of the mean, in MJy/sr, for the COMMENT 10 photometric measures, given in COMMENT the following order: 1A,2A,3A,4,5,6,7,8,9,10. COMMENT COMMENT The contents B of the Standard_Deviation fields COMMENT are given on a uniform logarithmic scale, COMMENT spanning 4 decades, having been calculated COMMENT from the standard deviations S (in MJy/sr) as follows: COMMENT if S <= 10**-N then B = 0 COMMENT if 10**-N < S < 10**(-N+4) then B = IFIX((N+log10(S))*254./4.)+1 COMMENT if S >= 10**(-N+4) then B = 255 COMMENT where the value of N is band-dependent, and given below. COMMENT COMMENT Conversely, the standard deviations COMMENT can be reconstructed by: COMMENT S <= 10**-N if B = 0 COMMENT S = 10**(4*(B-0.5)/254. - N) if 1 <= B <= 254 COMMENT S >= 10**(-N+4) if B = 255 COMMENT (The maximum error on the reconstructed value is 1.8 %) COMMENT COMMENT COMMENT The values of N are: COMMENT Bands 1A, 2A, 3A, 4: N = 4 COMMENT Bands 5, 6: N = 3 COMMENT Bands 7, 8: N = 2 COMMENT Band 9: N = 0 COMMENT Band 10: N = 1 COMMENT COMMENT Range of S = [10**-N,10**(-N+4)] TTYPE11 = 'StdDev ' / pipeline fieldname = Standard_Deviation TUNIT11 = 'MJy/sr ' / TFORM11 = '10B ' / TDIM11 = '(10) ' / COMMENT -------------------------------------------------------------------- COMMENT Standard deviation of the mean, in dimensionless units, COMMENT for Stokes parameters Q and U for Band 1, COMMENT Q and U for Band 2, and Q and U for Band 3. COMMENT COMMENT The contents B of the Stokes_Standard_Deviation fields COMMENT are given on a uniform logarithmic scale, COMMENT spanning 4 decades, having been calculated COMMENT from the standard deviations S (dimensionless) as follows: COMMENT if S <= 10**-4 then B = 0 COMMENT if 10**-4 < S < 1 then B = IFIX((4+log10(S))*254./4.)+1 COMMENT if S >= 1 then B = 255 COMMENT COMMENT Conversely, the standard deviations COMMENT can be reconstructed by: COMMENT S <= 10**-4 if B = 0 COMMENT S = 10**(4*(B-0.5)/254. - 4) if 1 <= B <= 254 COMMENT S >= 1 if B = 255 COMMENT (The maximum error on the reconstructed value is 1.8 %) COMMENT COMMENT COMMENT Range of S = [0.0001,1.0] TTYPE12 = 'StokesSD' / pipeline fieldname = Stokes_Standard_Deviation TUNIT12 = ' ' / TFORM12 = '6B ' / TDIM12 = '(6) ' / COMMENT -------------------------------------------------------------------- COMMENT Solar System Objects Flag COMMENT A one-byte flag which is used to signal COMMENT which solar-system objects' exclusion COMMENT zones intersect this pixel during COMMENT part or all of the time period COMMENT covered by the observations. COMMENT Data intersected by an exclusion zone COMMENT are not included in the photometric COMMENT or polarimetric averages. COMMENT If set, bits indicate intersection with COMMENT the exclusion zone of the following objects: COMMENT (Least significant bit = bit 0) COMMENT bit 0 --- Moon COMMENT bit 1 --- Mars COMMENT bit 2 --- Jupiter COMMENT bit 3 --- Saturn COMMENT bit 4 --- Uranus COMMENT bit 5 --- Neptune COMMENT bit 6 --- asteroids and comets COMMENT bit 7 --- spare TTYPE13 = 'SSOFlag ' / pipeline fieldname = Pixel_Quality_Flag, byte 3 TUNIT13 = ' ' / TFORM13 = '1B ' / COMMENT -------------------------------------------------------------------- COMMENT Fraction of Data Used COMMENT Three-byte flag indicating the fraction COMMENT of available data used in the generation COMMENT of the weekly averages. COMMENT Byte 1 : Average % of all the COMMENT available data that was used in COMMENT the construction of the averaged COMMENT observations for Bands 1A, 2A, 3A, COMMENT 4, 5, 6, 8, 9, and 10 COMMENT Range = [0,100%] COMMENT Byte 2 : Percent of the available Band 1B data COMMENT that was used. COMMENT Range = [0,100%] COMMENT Byte 3 : Percent of the available Band 7 data COMMENT that was used. COMMENT Range = [0,100%] TTYPE14 = 'FracUsed' / pipeline fieldname = Pixel_Quality_Flag,byte 4- TUNIT14 = ' ' / TFORM14 = '3B ' / TDIM14 = '(3) ' / TSCAL14 = 0.392 / bin size 100./(2**8 - 1) % TZERO14 = 0.0 / COMMENT -------------------------------------------------------------------- COMMENT Six-byte Flag indicating the quality of COMMENT data in each set of polarization ratios ( 1B/1A, COMMENT 1C/1A...,3C/3A), used to find the Stokes parameters. COMMENT If any of bits 0 through 4 are set, then the COMMENT values of the Stokes parameters COMMENT found from these ratios may be subject to error COMMENT beyond the formal uncertainties. COMMENT One byte per polarization ratio, given in the order COMMENT (1B/1A,1C/1A,2B/2A,2C/2A,3B/3A,3C/3A). COMMENT Each bit, if set, is interpreted as follows: COMMENT Least Significant Bit = Bit 0 COMMENT Bit 0: Only one ratio available. COMMENT Bit 1: Only two ratios available. COMMENT Bit 2: Between 3 and 9 ratios available. COMMENT Bit 3: Distribution of data such that the COMMENT Robust fitting used to deduce Stokes COMMENT parameters failed to converge. COMMENT Bit 4: Moon is within 25 degrees of boresight COMMENT for at least one of the polarization COMMENT ratios. COMMENT Bit 5: No ratios for 'C' channel: polarization COMMENT found from channel 'B' alone. COMMENT Bit 6: No ratios for 'B' channel: polarization COMMENT found from channel 'C' alone. COMMENT Bit 7: Processing of ratios failed to produce a value COMMENT of Q or U, or else set them to flag values. TTYPE15 = 'StokQual' / pipeline fieldname = Polarization_Quality_Flag TUNIT15 = ' ' / TFORM15 = '6B ' / TDIM15 = '(6) ' / COMMENT -------------------------------------------------------------------- END
