Spherical lamellar grating interferometer for airborne astronomical observations of far infrared objects

A lamellar-grating interferometer designed for airborne IR astronomy is described, and its response to a laboratory far-IR source and to Jupiter as viewed from NASA's Kuiper Airborne Observatory is discussed. The theory of lamellar-grating interferometers is reviewed, advantages over Michelson interferometers are noted, and the optical arrangement for the lamellar-grating instrument is indicated. The response of the instrument is illustrated using purged and unpurged spectra of a 1000-K blackbody source as well as a raw spectrum of Jupiter containing many absorption features (probably telluric) identified with rotation bands of H2O. It is noted that the interferometer's self-collimation allows for efficient operation with a minimum of auxiliary optics.