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Optics of Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII): Delay Lines and AlignmentWe 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 microns) 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 microns and 60-90 microns), and focuses them onto the detectors. It also separates out the NIR light (1-2.5 microns) 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.
Document ID
20170006225
Document Type
Conference Paper
External Source(s)
Authors
Dhabal, Arnab (Maryland Univ. College Park, MD, United States)
Rinehart, Stephen A. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Rizzo, Maxime J. (Maryland Univ. College Park, MD, United States)
Mundy, Lee (Maryland Univ. College Park, MD, United States)
Fixsen, Dale (Maryland Univ. College Park, MD, United States)
Sampler, Henry (NASA Goddard Space Flight Center Greenbelt, MD United States)
Mentzell, Eric (NASA Goddard Space Flight Center Greenbelt, MD United States)
Veach, Todd (Maryland Univ. College Park, MD, United States)
Silverberg, Robert F. (NASA Goddard Space Flight Center Greenbelt, MD, United States)
Furst, Stephen (North Carolina State Univ. Raleigh, NC, United States)
Dow, Thomas (North Carolina State Univ. Raleigh, NC, United States)
Ade, Peter (Cardiff Univ. United Kingdom)
Tucker, Carole (Cardiff Univ. United Kingdom)
Date Acquired
July 10, 2017
Publication Date
July 26, 2016
Publication Information
Publication: SPIE Proceedings
Volume: 9907
ISSN: 0277-786X
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN44107
Meeting Information
SPIE Optical and Infrared Interferometry and Imaging V Conference(Edinburgh)
Funding Number(s)
CONTRACT_GRANT: NNG17PT01A
Distribution Limits
Public
Copyright
Other

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