The Hyperspectral Infrared Imager (HyspIRI) spaceborne mission has two imaging sensors operating in the visible to shortwave infrared (VSWIR) and the thermal infrared (TIR), respectively. The HyspIRI-TIR imaging instrument is being developed for infrared mapping of the Earth in 8 spectral bands with a 5-day revisit time at the equator. The system will have 60-m ground resolution at nadir, 200-mK noise-equivalent temperature difference (NETD) for 300 K scenes, and 0.5 ºC absolute temperature accuracy. As the spacecraft moves in its polar orbit, a rotating scan mirror allows the telescope to view a 51º cross-track nadir strip, an internal blackbody target, and space, every 2.1 s. Combining the overlapping strips will yield a 51º (597-km) wide swath below the spacecraft.

The detector array will be 256×256 pixels in size and consist of 13.5-μm cutoff HgCdTe material delineated into 40-μm pixels. Eight spectral filters spanning 4 to 12 μm in wavelength will be assembled into a butcher-block assembly in close proximity to the detector array. Four columns of 256 detectors in each spectral channel will be combined using time delay and integration (TDI) to form a single 256-element-wide strip. A custom readout integrated circuit will provide the high speeds needed for the required 32-μs frame time.

This work was done by Marc C. Foote, Simon J. Hook, and William R. Johnson of Caltech for NASA’s Jet Propulsion Laboratory. NPO-48394

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This article first appeared in the June, 2014 issue of NASA Tech Briefs Magazine.

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