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D. Leisawitz (NASA GSFC), X. Zhang (RITSS and NASA GSFC), W. Danchi, D. Leviton, R. Lyon, A. Martino, J. C. Mather (NASA GSFC), L. G. Mundy (U. Maryland)
We describe the technique of wide field mosaic imaging for optical/IR interferometers and a laboratory instrument designed to validate, experiment with, and refine the technique. A conventional single-detector stellar interferometer operating with narrow bandwidth at center wavelength \lambda is limited in its field of view to the primary beam of the individual telescope apertures, or ~ \lambda / Dtel radians, where Dtel is the telescope diameter. Such a field is too small for many applications; often one wishes to image extended sources. We are developing and testing a technique analogous to the mosaicing method employed in millimeter and radio astronomy, but applicable to optical/IR Michelson interferometers. An Npix x Npix array detector placed in the image plane of the interferometer is used to record simultaneously the fringe patterns from many contiguous telescope fields, effectively multiplying the field size by Npix/2, where the factor 2 allows for Nyquist sampling. This technology will be especially valuable for far IR and submillimeter interferometric space observatories such as the Space Infrared Interferometric Telescope (SPIRIT) and the Submillimeter Probe of the Evolution of Cosmic Structure (SPECS). SPIRIT and SPECS will be designed to provide sensitive, high angular resolution observations of fields several arcminutes in diameter, and views of the universe complementary to those provided by HST, NGST, and ALMA. We present the first experimental results from the Wide-field Imaging Interferometry Testbed (WIIT) at NASA's Goddard Space Flight Center.