Interferometric Spectrometry for Infrared Astronomy

Abstract

In studies of the reflectivities and absorptivities of laboratory samples at frequencies below about 400 cm⁻¹, the spectrometric technique which uses a two-beam interferometer has shown clear advantages over dispersive (grating) spectrometry, and the most sophisticated interferometers can in many respects better dispersive instruments at higher frequencies than this, up to 10000 cm⁻¹. In infrared astronomy, too, similar advantages can be gained in the right circumstances (as shown by the impressive spectra of planetary atmospheres recorded by P. and J. Connes [1] and by the satellite-based measurements of atmospheric emission described by Hanel [2]). However, these advantages may not be as readily achieved in astronomy and it is the special considerations arising in applying interferometers to astronomical spectrometry which I wish to examine in this paper.