FITS Headers
DIRBE_DSZA_FACE5.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 = '10/06/97' / FITS file creation date (dd/mm/yy) DATE-MAP= '26/07/96' / 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 = 'FACE5 ' / 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 = 'DSZA_F5 ' / DIRBE Sky and Zodi Atlas, Face 5 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 ZLMODEL = 'FD6 ' / Version of DIRBE IPD model 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 = 127 / Number of 8 bit bytes in each row NAXIS2 = 2102039 / Number of rows PCOUNT = 0 / Number of bytes of data following table GCOUNT = 1 / Group count (always 1 for bintable extensions) TFIELDS = 10 / 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 Sky and Zodi Atlas (DSZA): Face 5 ------ COMMENT ---------------- Cryogenic Mission ------------------- COMMENT COMMENT The DSZA combines a subset of the photometric information COMMENT contained within the DIRBE Calibrated Annual File (DCAF) COMMENT with the modelled contribution of the interplanetary COMMENT dust (IPD) to the sky brightness at the ten DIRBE COMMENT wavelengths. COMMENT COMMENT The DSZA is organized in the same way as the DCAF. COMMENT Within the DSZA table, there are multiple row entries COMMENT for each pixel, one row for each mission week in which COMMENT a weekly averaged photometric answer was obtained for COMMENT that pixel. The multiple entries per pixel are sorted COMMENT in order of increasing observation time. A companion COMMENT Pixel Index is provided to facilitate data selection COMMENT and extraction. COMMENT COMMENT Each row of the DSZA table contains both the observed COMMENT weekly-averaged sky brightness in ten photometric bands, COMMENT plus the corresponding brightness predicted by the COMMENT DIRBE IPD Model for each wavelength band COMMENT at the same location and time of observation. COMMENT COMMENT For quality reasons, some of the weekly averaged COMMENT photometry which is recorded in the DCAF have been COMMENT replaced with a flagged (sentinel) value within the COMMENT DSZA. The following data were affected: COMMENT 1) mission week 04 (89345 - 89351), band 8 COMMENT 2) mission week 24 (90120 - 90126), bands 1-8 COMMENT 3) mission weeks 39 & 40 (90225 - 90238), bands 1-8 COMMENT COMMENT As with the DCAF, the DSZA has been divided into COMMENT 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 ******************************************************************* COMMENT -------------------------------------------------------------------- COMMENT ==================================================================== COMMENT Coordinate Information (Spatial and Temporal): COMMENT ==================================================================== COMMENT -------------------------------------------------------------------- COMMENT DIRBE Pixel number (resolution 9) TTYPE1 = 'Pixel_no' / entire fieldname = Pixel_no TUNIT1 = ' ' / TFORM1 = '1J ' / COMMENT ------------------------------------------------------------------- COMMENT Weekly Average Time of Observation, in International Atomic COMMENT Time (TAI) seconds elapsed since 01-JAN-1981:00:00:00.000 UTC. COMMENT This is the average of all the times at which the pixel was COMMENT observed during the DIRBE mission week represented by this COMMENT row of the FITS table, regardless of the weight assigned to COMMENT the individual observations. The time boundaries defining the COMMENT DIRBE Mission Weeks are documented in the DIRBE Explanatory COMMENT Supplement. TTYPE2 = 'Time ' / pipeline fieldname = Time TUNIT2 = 's ' / TFORM2 = '1D ' / COMMENT -------------------------------------------------------------------- COMMENT Difference between the weekly average time of observation COMMENT of the pixel for each photometric band, and the COMMENT weekly average time given in the TIME field (which is an COMMENT average of the times of ALL observations of the pixel). COMMENT Therefore, for each pixel: COMMENT Weekly average time of observation of Band x = COMMENT 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 TTYPE3 = 'DeltaT ' / pipeline fieldname = Delta_times TUNIT3 = 's ' / TFORM3 = '10B ' / TDIM3 = '(10) ' / TSCAL3 = 4725.0 / bin size (7*24*60*60)/(2**7) seconds TZERO3 = -602437.5 / offset to bin center in secs for unsigned byte COMMENT -------------------------------------------------------------------- COMMENT Weekly average solar elongation angle. COMMENT Solar elongation is defined as the angle between the vector COMMENT from the spacecraft to the center of the Sun and the DIRBE COMMENT line of sight. The weekly average solar elongation angle COMMENT is computed from the unweighted average of all the solar COMMENT elongation angles at which the pixel was observed during COMMENT the mission week represented by this row of the FITS table. COMMENT The mission week boundaries are given in the DIRBE COMMENT Explanatory Supplement. COMMENT Nominal range = [64,124] degrees TTYPE4 = 'SolElong' / pipeline fieldname = Elongation TUNIT4 = 'deg ' / TFORM4 = '1I ' / TSCAL4 = 0.0109867 / bin size 360/(2**15 -1) degrees TZERO4 = 0.00549333 / offset to bin center in degrees COMMENT -------------------------------------------------------------------- COMMENT ==================================================================== COMMENT DIRBE Sky Brightness 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. TTYPE5 = 'Photomet' / pipeline fieldname = Photometry TUNIT5 = 'MJy/sr ' / TFORM5 = '10E ' / TDIM5 = '(10) ' / COMMENT -------------------------------------------------------------------- COMMENT Number of observations of the pixel for this week COMMENT that contained at least one valid photometric measurement. TTYPE6 = 'NumRecs ' / pipeline fieldname = Num_recs TUNIT6 = ' ' / TFORM6 = '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. TTYPE7 = 'WtNumObs' / pipeline fieldname = Weighted_num_obs TUNIT7 = ' ' / TFORM7 = '10B ' / TDIM7 = '(10) ' / TSCAL7 = 0.50 / bin size 0.5 TZERO7 = 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)] TTYPE8 = 'StdDev ' / pipeline fieldname = Standard_Deviation TUNIT8 = 'MJy/sr ' / TFORM8 = '10B ' / TDIM8 = '(10) ' / 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 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 TTYPE9 = 'SSOFlag ' / pipeline fieldname = Pixel_Quality_Flag, byte 3 TUNIT9 = ' ' / TFORM9 = '1B ' / COMMENT -------------------------------------------------------------------- COMMENT ==================================================================== COMMENT DIRBE IPD Model Information: COMMENT ==================================================================== COMMENT -------------------------------------------------------------------- COMMENT Predicted spectral intensity, I(nu) in MJy/sr, of COMMENT the zodiacal light as computed using the DIRBE IPD model. COMMENT Model brightness is given for all 10 wavebands in COMMENT order of increasing wavelength, in direct correspondence COMMENT to the observed sky brightness listed in the 'Photomet' COMMENT field. As with the photometric measurements, the model COMMENT intensities are quoted at the nominal wavelength COMMENT for a source with nu*I(nu) = constant -- i.e., COMMENT a color correction is required to derive the true COMMENT spectral intensity, since the expected spectrum from COMMENT the IPD differs from nu*I(nu) = constant. COMMENT If data in the 'Photomet' field have been replaced by COMMENT flagged values in processing, then the 'ZL' field is COMMENT correspondingly set to a sentinel value of -16999. TTYPE10 = 'ZL ' / pipeline fieldname = ZL TUNIT10 = 'MJy/sr ' / TFORM10 = '10E ' / TDIM10 = '(10) ' / COMMENT -------------------------------------------------------------------- END
