The IRAS Sky Survey Atlas (ISSA) is a set of FITS images of the infrared sky at 12, 25, 60 and 100 µm. The ISSA images were made from coadded Infrared Astronomical Satellite (IRAS) survey data at moderate resolution. ISSA images are available online at the IRSA ISSA Image Server. ISSA is also available on permanent media from the NSSDC.

The scientific motivation for ISSA was to present the infrared sky as seen by IRAS at spatial scales greater than 5'. The combination of calibration improvements and the removal of most of the zodiacal emission results in a sensitivity that is limited by detector and confusion noise across most of the sky.

Full details of the ISSA images and their construction are given in the Explanatory Supplement to the IRAS Sky Survey Atlas available from the National Space Science Data Center (NSSDC) and IPAC.

Briefly, each ISSA image is 12.5 degrees by 12.5 degrees with 1.5' pixels. The spatial resolution is smoothed to the IRAS resolution at 100 µm (approximately 4' in-scan by 5' cross-scan) in all bands. The FITS images are either 16- or 32-bit images depending upon the noise level and dynamic range of the field. For each field and wavelength there are:

  • a coadded intensity image (denoted HCON 0)
  • intensity images for each of IRAS' three independent hours-confirmed sky coverages (denoted HCON 1, HCON 2 and HCON 3)
  • Scan coverage and noise images which are available from IPAC on request.

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(Characteristics of IRAS Data) (ISSA Processing Notes)