Fabrication and characterization of the Fizeau interferometer testbed

The Fizeau Interferometer Testbed (FIT) is a ground-based system that will be used for the development and testing of technologies relevant to Stellar Imager (SI) and other sparse aperture/Fizeau imaging interferometer mission concepts. The testbed will utilize image-based wavefront sensing and control to co-phase and maintain closed-loop control over a Sparse Aperture Array (SAA) consisting of spherical mirror elements. The SAA is a re-configurable assembly baselined to incorporate between seven (initially) and thirty 12.5mm diameter (R = 4000mm) mirror elements. In this paper we describe the fabrication, alignment, and initial calibration of the phase I (7 primary elements) FIT hardware and discuss various factors impacting the performance and stability of the testbed.