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Proceedings Paper

A novel imaging spectrometer form for the solar reflective spectral range for size, weight, and power limited applications
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Paper Abstract

The intense development in imaging spectrometers and related technology has yielded systems that are highly performing. Current grating-based designs utilize focal plane arrays with aberrations controlled to a fraction of a detector element and low F-numbers for high étendue to maximize the signal to noise performance. Tailored grating facets using two or more blaze angles optimize the optical efficiency across the full 400-2500 nm solar reflective spectral range. Two commonly used forms, the Offner-Chrisp and Dyson designs, are adaptations of microlithographic projectors with a concave or convex mirror replaced by a shaped grating; maintain a high degree of spatial-spectral uniformity. These gratings are relatively difficult to manufacture using either e-beam lithography or diamond machining. The challenge for optical designers is to create optical forms with reduced size, weight, and power (SWaP) requirements while maintaining high performance. We have focused our work in this area and are developing a breadboard prototype imaging spectrometer that covers the full VNIR/SWIR spectral range at 10 nm spectral sampling, has a large swath of 1500 spatial samples, and is compact. The current prototype is for an F/3.3 system that is 7 cm long with an 8 cm diameter with aberration control better than 0.1 pixel assuming an 18 μm pixel pitch. The form utilizes a catadioptric lens and a flat dual-blaze immersion grating. The flat grating simplifies manufacturing and we are currently exploring the manufacture of the grating through grayscale optical lithography where the entire pattern can be exposed at once without stitching errors.

Paper Details

Date Published: 23 October 2018
PDF: 7 pages
Proc. SPIE 10780, Multispectral, Hyperspectral, and Ultraspectral Remote Sensing Technology, Techniques and Applications VII, 107800L (23 October 2018); doi: 10.1117/12.2324453
Show Author Affiliations
Michael P. Chrisp, MIT Lincoln Lab. (United States)
Ronald B. Lockwood, MIT Lincoln Lab. (United States)
Melissa A. Smith, MIT Lincoln Lab. (United States)
Christopher Holtsberg, MIT Lincoln Lab. (United States)
Gregory Balonek, MIT Lincoln Lab. (United States)
Kurtis J. Thome, NASA Goddard Space Flight Ctr. (United States)
Sachidananda R. Babu, NASA Goddard Space Flight Ctr. (United States)
Parminder Ghuman, NASA Goddard Space Flight Ctr. (United States)

Published in SPIE Proceedings Vol. 10780:
Multispectral, Hyperspectral, and Ultraspectral Remote Sensing Technology, Techniques and Applications VII
Allen M. Larar; Makoto Suzuki; Jianyu Wang, Editor(s)

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