Lamellar Grating Interferometry at 50µ to Beyond 600µ from the Gerard P. Kuiper Airborne Observatory

Abstract

A lamellar grating interferometer of unique construction has been designed and successfully used on the Gerard P. Kuiper Airborne Observatory. The grating is spherical with the center of curvature in the prime focal plane of the telescope. This feature eliminates the need for collimating optics and thus improves the throughput of the system. Used in conjunction with a gallium doped germanium bolometer, cooled to liquid helium temperatures, the system is sensitive from 50µ to beyond 600µ with a present maximum resolving power λ/Δλ of 500 at 100µ and the system NEP was 2 x 10^-12 watts/H_z ^1/2. In flight the telescope operated open port ensuring minimum amount of attenuation. Observations were made with 20µ precipitable water above the aircraft. Interferograms were obtained of Jupiter at a resolution of 5cm^-1 and of Mars, Saturn and the Kleinmann-Low region in Orion at somewhat lower resolution. Results of these preliminary observations from our first flights will be presented. This project was supported by NASA grant NGR 33-019-127.