Interferometry at mid-infrared wavelengths: the ISI system

The ISI (Infrared Spatial Interferometer) involves three movable telescopes of Pfund design, each in trailers, each with a radiation collecting mirror 65 inches in diameter. The telescopes can be moved, and then set down on concrete pads for stability. They are located on Mt. Wilson, where pads have been arranged to give baselines varying from 4 to approximately 75 meters and oriented in various directions. Initial work, between 1988 and 2002, was done with two telescopes; the third telescope was added in 2003.