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Proceedings Paper

Alignment and performance of the Infrared Multi-Object Spectrometer
Author(s): Joseph A. Connelly; Raymond G. Ohl; J. Eric Mentzell; Timothy J. Madison; Jason E. Hylan; Ronald G. Mink; Timo T. Saha; June L. Tveekrem; Leroy M. Sparr; Victor John Chambers; Danette L. Fitzgerald; Matthew A. Greenhouse; John W. MacKenty
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Paper Abstract

The Infrared Multi-Object Spectrometer (IRMOS) is a principle investigator class instrument for the Kitt Peak National Observatory 4 and 2.1 m telescopes. IRMOS is a near-IR (0.8 - 2.5 μm) spectrometer with low- to mid-resolving power (R = 300 - 3000). IRMOS produces simultaneous spectra of ~100 objects in its 2.8 - 2.0 arc-min field of view (4 m telescope) using a commercial Micro Electro-Mechanical Systems (MEMS) micro-mirror array (MMA) from Texas Instruments. The IRMOS optical design consists of two imaging subsystems. The focal reducer images the focal plane of the telescope onto the MMA field stop, and the spectrograph images the MMA onto the detector. We describe ambient breadboard subsystem alignment and imaging performance of each stage independently, and ambient imaging performance of the fully assembled instrument. Interferometric measurements of subsystem wavefront error serve as a qualitative alignment guide, and are accomplished using a commercial, modified Twyman-Green laser unequal path interferometer. Image testing provides verification of the optomechanical alignment method and a measurement of near-angle scattered light due to mirror small-scale surface error. Image testing is performed at multiple field points. A mercury-argon pencil lamp provides a spectral line at 546.1 nm, a blackbody source provides a line at 1550 nm, and a CCD camera and IR camera are used as detectors. We use commercial optical modeling software to predict the point-spread function and its effect on instrument slit transmission and resolution. Our breadboard and instrument level test results validate this prediction. We conclude with an instrument performance prediction for cryogenic operation and first light in late 2003.

Paper Details

Date Published: 15 October 2003
PDF: 12 pages
Proc. SPIE 5172, Cryogenic Optical Systems and Instruments X, (15 October 2003); doi: 10.1117/12.503984
Show Author Affiliations
Joseph A. Connelly, NASA Goddard Space Flight Ctr. (United States)
Raymond G. Ohl, NASA Goddard Space Flight Ctr. (United States)
J. Eric Mentzell, NASA Goddard Space Flight Ctr. (United States)
Timothy J. Madison, NASA Goddard Space Flight Ctr. (United States)
Jason E. Hylan, Swales Aerospace (United States)
Ronald G. Mink, NASA Goddard Space Flight Ctr. (United States)
Timo T. Saha, NASA Goddard Space Flight Ctr. (United States)
June L. Tveekrem, NASA Goddard Space Flight Ctr. (United States)
Leroy M. Sparr, NASA Goddard Space Flight Ctr. (United States)
Victor John Chambers, NASA Goddard Space Flight Ctr. (United States)
Danette L. Fitzgerald, Cornell Univ. (United States)
Matthew A. Greenhouse, NASA Goddard Space Flight Ctr. (United States)
John W. MacKenty, Space Telescope Science Institute (United States)

Published in SPIE Proceedings Vol. 5172:
Cryogenic Optical Systems and Instruments X
James B. Heaney; Lawrence G. Burriesci, Editor(s)

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