Infrared Spatial Interferometer

Abstract

THe IR Spatial Interferometer (ISI) is an interferometer installed on Mt. Wilson and operating in the 10 micrometers wavelength region, using heterodyne detection and two movable 1.65 m telescopes. Its general technology and characteristics, recent changes, and observational results are broadly discussed. Some compensation for atmospheric path length fluctuations is demonstrated. Stellar observations show, among other characteristics, that many stars emit gas and dust episodically with times of 10-100 years between events, and that stellar diameters measured in the mid-IR region are about 10 percent larger than those measured with interferometry using visible light.