II. User's Guide to the WISE Preliminary Data Release


4. Ancillary Products

f. Atlas Image Inventory Table Format

The following table contains brief descriptions of all metadata information characterizing Atlas image data. The table also contains some processing-specific information as well as image statistics derived from the atlas images.

The columns in the following table are:


Column NameFormatUnitsnullsDescription 
band %1d ---- no WISE band number for the image.  
naxis %1d ---- no Number of data axes; it is always '2' for two-dimensional images.  
naxis1 %4d pixels no Length of data axis 1 or number of columns in the image.  
naxis2 %4d pixels no Length of data axis 2 or number of rows in the image.  
wrelease %20s ---- no The version number of the WISE multiframe pipeline used for this current data release.  
crpix1 %9.1f pixel no Axis 1 reference pixel at position crval1,crval2: 0.5*(naxis1+1)  
crpix2 %9.1f pixel no Axis 2 reference pixel at position crval1,crval2: 0.5*(naxis2+1)  
crval1 %16.12f degree no Reference Right Ascension at crpix1,crpix2 for EQUINOX.  
crval2 %16.12f degree no Reference Declination at crpix1,crpix2 for EQUINOX.  
ctype1 %13s ---- no Projection type for axis 1. It is always set to use the SIN (orthographic) projection; for the definition, see Calabretta & Greisen, 2002.  
ctype2 %13s ---- no Projection type for axis 2. It is always set to use the SIN (orthographic) projection; for the definition, see Calabretta & Greisen, 2002.  
equinox %6.1f year no Equinox of the World Coordinate System (WCS).  
bunit %20s ---- no Image pixel units: Data Number (DN) for intensity and uncertainty filetypes; "effective pixels" for the coverage filetype. Image filetypes are described in section II.3.  
elon %16.12f degrees no Ecliptic longitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
elat %16.12f degrees no Ecliptic latitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
glon %16.12f degrees no Galactic longitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
glat %16.12f degrees no Galactic latitude of the reference pixel. CAUTION: This coordinate should not be used as an astrometric reference.  
ra1 %16.12f degrees no Right ascension (J2000) at corner #1 (crpix1,crpix2=-0.5,-0.5)  
dec1 %16.12f degrees no Declination (J2000) at corner #1 (crpix1,crpix2=-0.5,-0.5)  
ra2 %16.12f degrees no Right ascension (J2000) at corner #2 (crpix1,crpix2=naxis1+0.5,-0.5)  
dec2 %16.12f degrees no Declination (J2000) at corner #2 (crpix1,crpix2=naxis1+0.5,-0.5)  
ra3 %16.12f degrees no Right ascension (J2000) at corner #3 (crpix1,crpix2=naxis1+0.5,naxis2+0.5)  
dec3 %16.12f degrees no Declination (J2000) at corner #3 (crpix1,crpix2=naxis1+0.5,naxis2+0.5)  
ra4 %16.12f degrees no Right ascension (J2000) at corner #4 (crpix1,crpix2=-0.5,naxis2+0.5)  
dec4 %16.12f degrees no Declination (J2000) at corner #4 (crpix1,crpix2=-0.5,naxis2+0.5)  
magzp %9.5f mag no Relative photometric zero-point magnitude for the image.  
magzpunc %8.6f mag no 1-sigma uncertainty in the photometric zero-point magnitude for the image.  
coadd_id %20s ---- no Atlas Tile identifier for the image. The identifier has the general form: RRRRsDDd_[trev], where
  • RRRR = Tile center RA in deci-degrees, truncated not rounded (e.g. RRRR=int[10*ra]).

  • s = Tile center Declination sign ("p"="+", "m"="-")

  • DDD = Tile center Declination in deci-degrees. For positive declinations, the tenths of a degree is truncated not rounded (e.g. DDD=int[10*dec]). For negative declinations, the tenths of a degree is always truncated leftward on the number line (e.g. DDD=ceil[10*abs(dec)].

  • [trev] = Disambiguation string.
    • t - Tile type ("a" = Atlas)
    • r - Data Release ("a" = Preliminary)
    • e - Sky coverage epoch ("1" = first)
    • v - Processing version.

    The disambiguation string is always aa11 for Tiles in the WISE Preliminary Data Release.

For example, the identifier of the Atlas Tile with center at (α,δ = 304.13896,-13.63000) is 3041m137_aa11.

 
fcdate %20s datetimeZ no Date and time of the image file creation, in Coordinated Universal Time (UTC).  
date_obs1 %24s datetimeZ no The date and time of the observation of the earliest frame in the coadd, UTC.  
date_obs2 %24s datetimeZ no The date and time of the observation of the latest frame in the coadd, UTC.  
sizex %9.6f degrees no Linear dimension of the coadd image along axis 1.  
sizey %9.6f degrees no Linear dimension of the coadd image along axis 2.  
pxscal1 %9.6f arcsec/pixel no Axis 1 arcsec per pixel scale at the reference pixel crpix1, crpix2.  
pxscal2 %9.6f arcsec/pixel no Axis 2 arcsec per pixel scale at the reference pixel crpix1, crpix2.  
moonrej %6d ---- no The number of image frames in the Tile rejected during coadd processing due to moon glow.  
mooninp %6d ---- no The initial number of input frames in the Tile with suspected moon glow.  
medint %10.3f DN no The median of the intensity pixels in the Atlas image.  
medcov %10.3f pixel no The median depth of coverage in the Atlas image.  
mincov %10.3f pixel no The minimum depth of coverage in the Atlas image.  
maxcov %10.3f pixel no The maxmimum depth of coverage in the Atlas image.  
lowcovpc %7.3f pixel no The percentage area of the coadd footprint with coverage depth ≤ 5 pixels.  
nomcovpc %7.3f pixel no The percentage area of coadd footprint with coverage depth ≤ 8 pixels.  
robsig %14.6f DN no Robust spatial sigma of the pixels with depth-of-coverage within the interval of the median ± 0.25. The sigma is computed from a trimmed standard-deviation from the mode using only the lower-tail of the intensity pixel distribution. Band dependent.  
pixchis1 %11.6f ---- no A pseudo-χ2 measure computed from the ratio: ROBSIG/(median of uncertainty pixels) for depths-of-coverage falling within: MEDCOV +/- 0.25. See also section II.3.e.i. Band dependent.  
pixchis2 %11.6f ---- no A pseudo-χ2 measure computed from the ratio: ROBSIG/(mode of uncertainty pixels) for depths-of-coverage falling within: MEDCOV +/- 0.25. See also section II.3.e.i. Band dependent.  
mednmsk %10.1f ---- no The median number of masked pixels per frame in the frames used in the coadd.  
cdelt1 %21.18f degrees/pixel no Axis 1 pixel scale at the reference pixel crpix1, crpix2, in degrees per pixel. See pxscal1 for the arcsec equivalent.  
cdelt2 %21.18f degrees/pixel no Axis 2 pixel scale at the reference pixel crpix1, crpix2, in degrees per pixel. See pxscal2 for the arcsec equivalent.  
crota2 %18.13f degrees no Image twist: the position of the image y-axis West of North at the EQUINOX in the opposite direction of the conventional Position Angle, where position angle (P.A.) = -CROTA for J2000.  
bitmask %9d degrees no Fatal bitstring mask template used to signal rejected input frame pixels. The bits are defined here. The values are band-dependent.  
numfrms %5d degrees no The number of image frames used to create the coadd.  
qa_status %9s ---- no This string indicates Quality Assurance status for the Tile:
  • "Prelim" means only preliminary Quality Assurance has been performed by the automated QA subsystem;
  • "Reviewed" means the QA data has been examined and scores corrected by a QA team member;
  • "Final" means the QA scores have been finalized. All Atlas Tiles fall into this category.
 
qual_coadd %2d ---- no This integer indicates the quality score value for the Tile, with values of 0 (poor quality) or 10 (high quality). All Atlas Tiles have received quality scores of 10. The value is determined by the minimum of the quality factors qc_fact, qa_fact, and qi_fact, multiplied by ten.  
qc_fact %3.1f ---- no This quality factor gauges the quality of completion. If the status value from the Multiframe pipeline was equal to 0 (indicating a problem-free completion), then qc=1.0. Otherwise, qc=0.0 because the coadd failed to complete processing. All Atlas Tiles have received qc values of 1.0.  
qi_fact %3.1f ---- no This quality factor gauges the image shape quality. It checks for potential image smearing by using the axial ratio of the PSF calculated from a subset of sources in the Tile. The value of qi is 1.0 if the axial ratio b/a > 0.60; otherwise it is 0.0. All Atlas Tiles have received qi values of 1.0.  
qa_fact %3.1f ---- no This factor gauges the astrometric quality. If the standard deviation of WISE positions with respect to the 2MASS Point Source Catalog positions is < 0.5 arcsec on each axis (or 0.71 arcsec RSS), for sources having SNR > 20 in at least one band, then qa=1.0. Otherwise, qa=0.0. All Atlas Tiles have received qa values of 1.0.  
date_imgprep %20s datetimeZ no The date and time when the data was prepared by the WISE archive software DBPREP for the archive loading, in UTC.  
load_id %4d ---- no A unique integer that identifies the archive data load batch in the archive ingest procedure that contains the Altas image.  
cntr %12d ---- no Unique sequential identification number for the image metadata table entry.  

Last Update: 2011 April 11


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