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Proceedings Paper

Fizeau interferometry testbed: wavefront control
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Paper Abstract

Stellar Imager (SI) is a potential 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 control would be required to initially align the formation and maintain alignment during science observations and after array reconfiguration. The Fizeau Interferometry Testbed (FIT) is a testbed currently under development at the NASA/Goddard Space Flight Center to develop and study the wavefront control methodologies for Stellar Imager and other large, sparse aperture telescope systems. FIT consists of 7 articulated spherical mirrors in a Golay pattern, expandable up to 30 elements, and reconfigurable into multiple array patterns. FIT’s purpose is to demonstrate image quality versus array configuration and to develop and advance the wavefront control for SI. FIT uses extended scene wavelength, focus and field diversity to estimate the wavefront across the set of apertures. The recovered wavefront is decomposed into the eigenmodes of the control matrix and actuators are moved to minimize the wavefront piston, tip and tilt. Each mirror’s actuators are 3 degrees of freedom, however, they do not move each of the mirrors about a point on each mirrors surface, thus the mapping from wavefront piston, tip/tilt to mirror piston, tip/tilt is not diagonal. We initially estimate this mapping but update it as part of wavefront sensing and control process using system identification techniques. We discuss the FIT testbed, wavefront control methodology, and show initial results from FIT.

Paper Details

Date Published: 12 October 2004
PDF: 12 pages
Proc. SPIE 5487, Optical, Infrared, and Millimeter Space Telescopes, (12 October 2004); doi: 10.1117/12.552198
Show Author Affiliations
Richard G. Lyon, NASA Goddard Space Flight Ctr. (United States)
Kenneth G. Carpenter, NASA Goddard Space Flight Ctr. (United States)
Lisa Mazzuca, NASA Goddard Space Flight Ctr. (United States)
Hubert Huet, Sigma Space Corp. (United States)
Paul W. Cottle, Sigma Space Corp. (United States)
Peter P. Petrone III, Sigma Space Corp. (United States)
NASA Goddard Space Flight Ctr. (United States)
Peter Dagoda, Sigma Space Corp. (United States)
NASA Goddard Space Flight Ctr. (United States)
Peter Liiva, Sigma Space Corp. (United States)
Joe Marzouk, Sigma Space Corp. (United States)
Gregory Solyar, Univ. of Maryland/Baltimore County (United States)
David Mozurkewich, Seabrook Engineering (United States)
Xiaolei Zhang, Naval Research Lab. (United States)
Thomas Armstrong, Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 5487:
Optical, Infrared, and Millimeter Space Telescopes
John C. Mather, Editor(s)

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