Building the Fizeau interferometer testbed

The Fizeau interferometer testbed (FIT) is a collaborative effort between NASA's Goddard Space Flight Center, the Naval Research Laboratory, Sigma Research and Engineering Corp., and the University of Maryland. The testbed is used to explore the principles of and the requirements for the full, as well as the pathfinder, stellar imager mission concept. It has a long-term goal of demonstrating closed-loop control of a sparse array of numerous articulated mirrors to keep optical beams in phase and optimize interferometric synthesis imaging. Herein, we describe the optical, mechanical, data acquisition system, dispersed fringe sensor and discuss the wavefront sensing and control algorithms. We describe the initial alignment of the 7-element version of the system, which has now been completed. Calibration and initial data acquisition of this setup is currently underway and results are shown from the initial phasing of the array. Finally, future plans for FIT are briefly noted.