  The Wide-Field Imaging Interferometry Testbed (WIIT) will provide valuable
information for the development of space-based interferometers. This laboratory
instrument operates at optical wavelengths and provides the ability to test
operational algorithms and techniques for data reduction of interferometric
data. Here we present some details of the system design and implementation,
discuss the overall performance of the system to date, and present our plans
for future development of WIIT. In order to make best use of the
interferometric data obtained with this system, it is critical to limit
uncertainties within the system and to accurately understand possible sources
of error. The WIIT design addresses these criteria through a number of
ancillary systems. The use of redundant metrology systems is one of the most
important features of WIIT, and provides knowledge of the delay line position
to better than 10 nm. A light power detector is used to monitor the brightness
of our light sources to ensure that small fluctuations in brightness do not
affect overall performance. We have placed temperature sensors on critical
components of the instrument, and on the optical table, in order to assess
environmental effects on the system. The use of these systems provides us with
estimates of the overall system uncertainty, and allows an overall
characterization of the results to date. These estimates allow us to proceed
forward with WIIT, adding rotation stages for 2-D interferometry. In addition,
they suggest possible avenues for system improvement. Funding for WIIT is
provided by NASA Headquarters through the ROSS/SARA Program and by the Goddard
Space Flight Center through the IR&D Program.
