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Proceedings Paper

Optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): delay lines and alignment
Author(s): Arnab Dhabal; Stephen A. Rinehart; Maxime J. Rizzo; Lee Mundy; Dale Fixsen; Henry Sampler; Eric Mentzell; Todd Veach; Robert F. Silverberg; Stephen Furst; Thomas Dow; Peter Ade; Carole Tucker
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Paper Abstract

We present the optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII) as it gets ready for launch. BETTII is an 8-meter baseline far-infrared (30-90 μm) interferometer mission with capabilities of spatially resolved spectroscopy aimed at studying star formation and galaxy evolution. The instrument collects light from its two arms, makes them interfere, divides them into two science channels (30-50 μm and 60-90 μm), and focuses them onto the detectors. It also separates out the NIR light (1-2.5 μm) and uses it for tip-tilt corrections of the telescope pointing. Currently, all the optical elements have been fabricated, heat treated, coated appropriately and are mounted on their respective assemblies. We are presenting the optical design challenges for such a balloon borne spatio- spectral interferometer, and discuss how they have been mitigated. The warm and cold delay lines are an important part of this optics train. The warm delay line corrects for path length differences between the left and the right arm due to balloon pendulation, while the cold delay line is aimed at introducing a systematic path length difference, thereby generating our interferograms from where we can derive information about the spectra. The details of their design and the results of the testing of these opto-mechanical parts are also discussed. The sensitivities of different optical elements on the interferograms produced have been determined with the help of simulations using FRED software package. Accordingly, an alignment plan is drawn up which makes use of a laser tracker, a CMM, theodolites and a LUPI interferometer.

Paper Details

Date Published: 26 July 2016
PDF: 12 pages
Proc. SPIE 9907, Optical and Infrared Interferometry and Imaging V, 99070T (26 July 2016); doi: 10.1117/12.2230218
Show Author Affiliations
Arnab Dhabal, NASA Goddard Space Flight Ctr. (United States)
Univ. of Maryland, College Park (United States)
Stephen A. Rinehart, NASA Goddard Space Flight Ctr. (United States)
Maxime J. Rizzo, NASA Goddard Space Flight Ctr. (United States)
Univ. of Maryland, College Park (United States)
Lee Mundy, Univ. of Maryland, College Park (United States)
Dale Fixsen, NASA Goddard Space Flight Ctr. (United States)
Henry Sampler, NASA Goddard Space Flight Ctr. (United States)
Eric Mentzell, NASA Goddard Space Flight Ctr. (United States)
Todd Veach, NASA Goddard Space Flight Ctr. (United States)
Robert F. Silverberg, NASA Goddard Space Flight Ctr. (United States)
Stephen Furst, North Carolina State Univ. (United States)
Thomas Dow, North Carolina State Univ. (United States)
Peter Ade, Cardiff Univ. (United Kingdom)
Carole Tucker, Cardiff Univ. (United Kingdom)


Published in SPIE Proceedings Vol. 9907:
Optical and Infrared Interferometry and Imaging V
Fabien Malbet; Michelle J. Creech-Eakman; Peter G. Tuthill, Editor(s)

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