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Proceedings Paper

Texas echelon cross echelle spectrograph
Author(s): John H. Lacy; Matthew J. Richter; Wanglong Yu; Bianca S. Basso
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Paper Abstract

A new mid-IR spectrograph, the Texas Echelon Cross Echelle Spectrograph (TEXES) is under construction. The primary motivation for TEXES is to observe interstellar molecules at very high resolution. TEXES will operate at 7-25 micrometers wavelength with three spectrographic modes: a high resolution cross-dispersed mode, with R approximately equals 100,000, a mid-resolution long-slit mode, with R approximately equals 14,000, and a low resolution long-slit mode, with R approximately equals 2000. In hi-res mode, the primary disperser is a 36 inch long, R10 grating with a 7 mm groove spacing. The echelon is cross-dispersed with a 7 in long R2 echelle. In mid-res mode, the echelon is by-passed with an Offner relay, and the echelle is used by itself. In lo-res mode, a first-order grating is inserted over the echelle. For initial test, TEXES will use a Hughes Aircraft 20 X 64 pixel Si:As impurity-band array, which covers only two echelon orders. It will later be replaced with a 256 X 256 pixel array, which will Nyquist sample approximately 10 orders. The spectrograph has been assembled and tested with a partially complete echelon, demonstrating the soundness of the design. When we began this project, we were unable to find a vendor capable of machining or ruling a diffraction grating with the very coarse ruling required. Consequently, we attempted to hand-fabricate the echelon. We have not succeeded in assembling the echelon with the required precision, missing by about a factor of two. Fortunately, Hyperfine, Inc. is now capable of diamond machining the echelon. We are purchasing a machined echelon, and hope to complete the spectrograph by the end of summer 1998.

Paper Details

Date Published: 21 August 1998
PDF: 12 pages
Proc. SPIE 3354, Infrared Astronomical Instrumentation, (21 August 1998); doi: 10.1117/12.317269
Show Author Affiliations
John H. Lacy, Univ. of Texas/Austin (United States)
Matthew J. Richter, Univ. of Texas/Austin (United States)
Wanglong Yu, Univ. of Texas/Austin (United States)
Bianca S. Basso, Univ. of Texas/Austin (United States)

Published in SPIE Proceedings Vol. 3354:
Infrared Astronomical Instrumentation
Albert M. Fowler, Editor(s)

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