Aerospace LWIR Instrumentation

Aerospace LWIR Instrumentation

First published Summer 2011, Crosslink® magazine.


False-color LWIR radiance image mosaic acquired by Mako

False-color LWIR radiance image mosaic acquired by Mako in a single 4-minute pass over an area of exposed complex geological structure in California’s Imperial Valley. To cover the equivalent area with SEBASS would require 45 passes and more than 3 hours of flight time.

The research described in this article was possible in part by airborne deployments of the Spatially Enhanced Broadband Array Spectrograph System (SEBASS). First commissioned in 1995, SEBASS is a nadir-viewing, roll-compensated, pushbroom hyperspectral imager comprising two spectrographs, one operating in the midwave infrared (MWIR) region at 2.9–5.2 microns, and the other in the LWIR region at 7.8–13.4 microns. Each uses a single cooled focal-plane array with 128 spatial pixels and 128 spectral pixels. While SEBASS is a thoroughly field-proven system, its narrow field-of-regard (125-meter swath from an altitude of 3000 feet) limits the area that can be covered during a typical flight and thus constrains the scope of the studies it can support. Future investigations will alleviate this shortcoming by employing a wide-swath, three-axis-stabilized, whiskbroom hyperspectral LWIR instrument (named Mako) that concluded its inaugural airborne trials in September 2010. Built under an Aerospace corporate research initiative, Mako will offer up to 15 times the SEBASS areal coverage rate while matching its radiometric performance and spatial resolution.

Aerospace is also completing a NASA-funded effort to develop a 32-channel LWIR imager optimized for retrieving surface composition and atmospheric trace gas content. The instrument, named MAGI (Mineral and Gas Identifier), will have three-axis-stabilized whiskbroom scanning ability for wide-swath performance suited to Earth science applications. Both Mako and MAGI feature novel compact spectrometer designs that can operate at low f-number with low optical distortion. Each is intended for use in fundamental science investigations and to function as test beds to assist in the definition of future space-based instrument concepts.

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