Development of infrared interferometry for upper atmospheric emission studies

Abstract

This paper is a review of the historical development of the Michelson interferometer into modern-day Fourier transform spectrometry (FTS) used for upper atmospheric emission studies in the near IR. For the period of the last decade, the focus of the review is upon USAF/USU interferometric instruments. Michelson invented the "cross beam" interferometer in 1880; however, the first interferogram was not reported until that of Wood in 1911. Fellgett deduced the multiplex advantage in 1949. By the early 1950s, both Jacqui-not and Rupert had pointed out the throughput advantage, and Fellgett and Strong had each obtained Fourier transforms of interferograms. In 1959, J. Connes and Gush obtained a spectrum of the nighttime IR airglow in 30 min using a Michelson interferometer. In 1962 Gush and Buijs flew an interferometer aboard a balloon to obtain spectra from the airglow. Mertz and M. Block developed a commercial Michelson interferometer in about 1959. L. Block of AFCRL flew a Michelson interferometer aboard a satellite in 1962. In 1965, Connes and Connes obtained high-resolution spectra of planets using cat's-eye retroreflectors coupled with an interferometrically controlled step and integrate method. NASA successfully flew an interferometer aboard a satellite in 1969, which led to including FTS experiments on the planetary probes. In 1965 Tukey and Cooley published their FFT computer program based upon the algorithm of Good. AFGL/USU applied the FFT algorithm to FTS that same year. Stair launched a rocketborne liquid-He cooled interferometer in 1976 which obtained spectra of earth limb emissions. Mertz in 1959 approached field-of-view widening of an interferometer using variable thickness glass compensator plates. Baker and his USU staff used the Connes-Bouchareine compensation method to develop a series of wide-angle Michelson interferometers (WAMIs) for airglow and auroral studies. In 1973, they created a cryogenic WAMI to obtain an IR airglow spectrum in only 10 sec. A rocketborne version was successfully flown to obtain airglow spectra in 1979. This instrument took a 2-cm(-1) interferogram in 1 sec., used a liquid-He cooled detector to cover the 2-8-microm range, and the NESR was 3 x 10(-13) W cm(-2) sr(-1)/cm(-1) at 5 microm.