Exposure time for space-borne ir spatial interferometer

A mathematical analysis is performed to determine the relationship between the signal-to-noise ratio and the exposure time for an orbiting IR heterodyne spatial interferometer. The analysis includes consideration of the transformation of the interferogram to obtain the source angular intensity distribution so that the signal-to-noise ratio pertains to the angular distribution rather than to the interferogram. The analysis is applied to a number of known IR sources. The results presented show that an interferometer with a 30-m baseline using half-meter telescopes should be able to image a source such as IRC + 30219 with a signal-to-noise ratio of 10 in a total exposure time of less than an hour.