ABOUT LAMBDA

FITS Headers

DIRBE_DCAF_P3B_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    = '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  = '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 = 'DCAF_F5 '           / DIRBE Calibrated Annual File, 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 
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  =              2102039 / 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 5 -----          
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                                                                             

A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason