Tech Briefs

High-Speed Spectral Mapper

NASA’s Jet Propulsion Laboratory, Pasadena, California

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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