HARDI: A High Angular Resolution Deployable Interferometer For Space

We describe here a proposed orbiting interferometer covering the UV, visible and near IR spectral ranges. With a 6-meter baseline and a collecting area equivalent to about a 1.4 meter diameter full aperture, this instrument will offer significant improvements in resolution over the Hubble Space Telescope, and complement the new generation of ground-based interferometers with much better limiting magnitude and spectral coverage. On the other hand, it has been designed as a considerably less ambitious project (one launch) than other current proposals. We believe that this concept is feasible given current technological capabilities, yet would serve to prove the concepts necessary for the much larger systems that must eventually be flown. The interferometer is of the Fizeau type. It therefore has a much larger field (for guiding) and better UV throughput (only 4 surfaces) than phased arrays. Optimized aperture configurations and ideas for the cophasing and coalignment systems are presented. The interferometer would be placed in a geosynchronous or 6-pm sunsynchronous orbit to minimize thermal and mechanical disturbances and to maximize observing efficiency.