<title>Algorithms for calibration and point-source extraction for a LWIR space-based sensor</title>

Abstract

The Midcourse Space Experiment (MSX) satellite is scheduled for launch in early 1996. The Spatial Infrared Imaging Telescope (SPIRIT) III sensor, the primary instrument of MSX, covers the spectrum from the midwave infrared to the longwave infrared. The SPIRIT III instrument is cryogenically cooled and consists of an interferometer and a five-band scanning radiometer with a spatial resolution of 90 (mu) rad. This paper describes the unique algorithms and software implementation developed to support the SPIRIT III radiometer. The algorithms for converting raw radiometer counts to calibrated counts and then to engineering units are described. The standard process (raw counts to corrected counts) consists of dark offset correction, linearity correction, integration mode normalization, non-uniformity correction, field of regard non-uniformity correction, and bad pixel processing. The algorithm to convert corrected counts to point source engineering units consist of pixel position tagging (non-uniform grid), color coalignment, distortion correction, background subtraction, correction for spacecraft attitude, and position and amplitude determination. The algorithms implemented in the software must produce goniometric estimates to within 5 (mu) rad (0.05 pixel) and radiometric results to within 1 percent. The results of the algorithms are demonstrated in this paper.