A silicon and KRS-5 grism suite for FORCAST on SOFIA

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

doi:10.1117/12.788565

9 July 2008 A silicon and KRS-5 grism suite for FORCAST on SOFIA

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

Author Affiliations +

Proceedings Volume 7014, Ground-based and Airborne Instrumentation for Astronomy II; 70142C (2008) https://doi.org/10.1117/12.788565
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

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.

Citation Download Citation

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, and Terry Herter "A silicon and KRS-5 grism suite for FORCAST on SOFIA", Proc. SPIE 7014, Ground-based and Airborne Instrumentation for Astronomy II, 70142C (9 July 2008); https://doi.org/10.1117/12.788565

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