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Proceedings Paper

Wavefront sensing and closed-loop control for the Fizeau interferometry testbed
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Paper Abstract

Stellar Imager (SI) is a proposed NASA space-based UV imaging interferometer to resolve the stellar disks of nearby stars. SI would consist of 20 - 30 separate spacecraft flying in formation at the Earth-Sun L2 libration point. Onboard wavefront sensing and control is required to maintain alignment during science observations and after array reconfigurations. The Fizeau Interferometry Testbed (FIT), developed at the NASA/Goddard Space Flight Center, is being used to study wavefront sensing and control methodologies for Stellar Imager and other large, sparse aperture telescope systems. FIT initially consists of 7 articulated spherical mirrors in a Golay pattern, and is currently undergoing expansion to 18 elements. FIT currently uses in-focus whitelight sparse aperture PSFs and a direct solve phase retrieval algorithm to sense and control its wavefront. Ultimately it will use extended scene wavelength, with a sequential diversity algorithm that modulates a subset of aperture pistons to jointly estimate the wavefront and the reconstructed image from extended scenes. The recovered wavefront is decomposed into the eigenmodes of the control matrix and actuators are moved to minimize the wavefront piston, tip and tilt in closed-loop. We discuss the testbed, wavefront control methodology and ongoing work to increase its bandwidth from 1 per 11 seconds to a few 10's of Hertz and show ongoing results.

Paper Details

Date Published: 21 September 2007
PDF: 12 pages
Proc. SPIE 6687, UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III, 66870H (21 September 2007); doi: 10.1117/12.731761
Show Author Affiliations
Richard G. Lyon, NASA Goddard Space Flight Ctr. (United States)
Kenneth G. Carpenter, NASA Goddard Space Flight Ctr. (United States)
Alice Liu, NASA Goddard Space Flight Ctr. (United States)
Peter Petrone, Sigma Space (United States)
Peter Dogoda, Sigma Space (United States)
Daniel Reed, Sigma Space (United States)
David Mozurkewich, Seabrook Engineering (United States)

Published in SPIE Proceedings Vol. 6687:
UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts III
Howard A. MacEwen; James B. Breckinridge, Editor(s)

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