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Proceedings Paper

A silicon and KRS-5 grism suite for FORCAST on SOFIA
Author(s): Casey P. Deen; Luke Keller; Kimberly A. Ennico; Daniel T. Jaffe; Jasmina P. Marsh; Joseph D. Adams; Nirbhik Chitrakar; Thomas P. Greene; Douglas J. Mar; Terry Herter
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Paper Abstract

We have designed and fabricated a suite of grisms for use in FORCAST, a mid-infrared camera scheduled as a first-light instrument on SOFIA. The grism suite gives SOFIA a new capability: low and moderate resolution spectroscopy from 5μm to 37μm, without the addition of a new instrument. One feature of the optical design is that it includes a mode using pairs of cross-dispersed grisms, providing continuous wavelength coverage over a broad range at higher resolving power. We fabricated four silicon (n = 3.44) grisms using photolithographic techniques and purchased two additional mechanically ruled KRS-5 (n = 2.3) grisms. One pair of silicon grisms permits observations of the 5 - 8μm band with a long slit at R~ 200 or, in a cross-dispersed mode, at resolving powers up to 1500. In the 8 - 14μm region, where silicon absorbs heavily, the KRS-5 grisms produce resolving powers of 300 and 800 in long-slit and cross-dispersed mode, respectively. The remaining two silicon grisms cover 17 - 37μm at resolving powers of 140 and 250. We have thoroughly tested the silicon grisms in the laboratory, measuring efficiencies in transmission at 1.4 - 1.8μm. We report on these measurements as well as on cryogenic performance tests of the silicon and KRS-5 devices after installation in FORCAST.

Paper Details

Date Published: 9 July 2008
PDF: 10 pages
Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70142C (9 July 2008); doi: 10.1117/12.788565
Show Author Affiliations
Casey P. Deen, Univ. of Texas at Austin (United States)
Luke Keller, Ithaca College (United States)
Kimberly A. Ennico, NASA Ames Research Ctr. (United States)
Daniel T. Jaffe, Univ. of Texas at Austin (United States)
Jasmina P. Marsh, Univ. of Texas at Austin (United States)
Joseph D. Adams, Cornell Univ. (United States)
Nirbhik Chitrakar, Ithaca College (United States)
Thomas P. Greene, NASA Ames Research Ctr. (United States)
Douglas J. Mar, Univ. of Texas at Austin (United States)
Terry Herter, Cornell Univ. (United States)

Published in SPIE Proceedings Vol. 7014:
Ground-based and Airborne Instrumentation for Astronomy II
Ian S. McLean; Mark M. Casali, Editor(s)

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