Key to IGA Image Data Columns

All the data returned from the search are listed in tabular form on the results page. Any source tables found are listed first, followed by images. This help page explains the format and columns of the image metadata table (standard flat ascii file in IPAC format) and the summary listings table with image data download links.

Image Metadata Table

Atlas image metadata will contain the following keyword to denote that the metadata describes images: "\datatype=fitshdr". The IGA column header is as follows:

     |  cntr | ra | dec | cra | cdec | naxis1 |  naxis2 | ctype1 | ctype2 |   crpix1 |   crpix2 |
         crval1   |    crval2   |   cdelt1  |   cdelt2  |   crota2    |equinox |      ra4    |
          dec4    |      ra3    |     dec3    |      ra2    |     dec2    |      ra1    |
          dec1    | hdu  | fname                              |   band | iteration |

Below is the key describing each column name found in the Atlas IGA image metadata table.

Column Name Column Data Type Short Definition Standard FITS Keyword (Y/N)
cntr int A unique counter (row number) N
ra double Right Ascension in Equatorial J2000 N
dec double Declination in Equatorial J2000 N
cra char Right Ascension in sexagesimal format HHMMSS J2000 N
cdec char Declination in sexagesimal format DDMMSS J2000 N
naxis1 int The size of the image in pixels for dimension 1 Y
naxis2 int The size of the image in pixels for dimension 2 Y
ctype1 char The coordinate system (first four characters) and WCS map projection (last three characters) for dimension 1 Y
ctype2 char The coordinate system (first four characters) and WCS map projection (last three characters) for dimension 2 Y
crpix1 double The pixel coordinate of the reference location (can be fractional, in the image center or off the image) for dimension 1 Y
crpix2 double The pixel coordinate of the reference location (can be fractional, in the image center or off the image) for dimension 2 Y
crval1 double The coordinate of a reference location on the sky (often at the center of the image) for dimension 1 Y
crval2 double The coordinate of a reference location on the sky (often at the center of the image) for dimension 2 Y
cdelt1 double The pixel scale (in degrees on the sky per pixel) at the reference location for dimension 1 Y
cdelt2 double The pixel scale (in degrees on the sky per pixel) at the reference location for dimension 2 Y
crota2 double The rotation angle from the "up" direction to the celestial pole Y
equinox double Precessional year associated with the coordinate system Y
ra4 double RA position of the upper left image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra4, dec4) = (0.5, NAXIS2 + 0.5)] N
dec4 double Dec position of the upper left image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra4, dec4) = (0.5, NAXIS2 + 0.5)] N
ra3 double RA position of the upper right image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra3, dec3) = (NAXIS1 + 0.5, NAXIS2 + 0.5)] N
dec3 double Dec position of the upper right image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra3, dec3) = (NAXIS1 + 0.5, NAXIS2 + 0.5)] N
ra2 double RA position of the lower right image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra2, dec2) = (NAXIS1 + 0.5, 0.5)] N
dec2 double Dec position of the lower right image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra2, dec2) = (NAXIS1 + 0.5, 0.5)] N
ra1 double RA position of the lower left image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra1, dec1) = (0.5, 0.5)] N
dec1 double Dec position of the lower left image corner [pixel space, where first pixel is located at (0.5, 0.5), position (ra1, dec1) = (0.5, 0.5)] N
hdu int Fits Header Data Unit (extension) of the image data Y
fname char The path to the FITS file (used in creating the http link for downloading) N
band int Wavelength band is 3 (60 micron) or 4 (100 micron) N
iteration int Number of processing iterations performed on the data: 1 or 20 of the HIRES algorithm N
download char Links to download the fits datafile to disk or to send it to the OASIS Applet for viewing N

Summary Listings Table (Images)

The image metadata are summarized within the "Listing of Image Results" section. The ra, dec, naxis1, naxis2, band, iteration and fname columns come directly from the metadata table; these are described in the table above. There is also a "download" column containing an HTTP link to the image file in order to download it to disk, and an OASIS link in order to send this same image file to the OASIS applet viewer.

Click here for more information the ascii IPAC table format. Instructions