Submillimetre-wave solar observations using a double-output Michelson interferometer

• Published in: Infrared physics Vol. 11; no. 1; pp. 1 - 23
• Main Authors: Burroughs, W.J., Chamberlain, J.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.1971
• ISSN: 0020-0891
• DOI: 10.1016/0020-0891(71)90030-3

A double-output Michelson-type interferometer having Golay cell detectors has been used at an altitude of 3580 m to study, by means of Fourier spectrometry, the atmospheric absorption of solar radiation in the submillimetre-wave region. Spectra having 0.5, 0.25 and 0.125 cm -1 resolution were obtained. The 0.5 cm -1 results have been compared with spectra obtained with the same instrument in the laboratory using a mercury lamp source. At higher resolution the spectroscopic results have revealed features due to atmospheric oxygen and ozone, and have also shown that quantitative estimates of the integrated water content of the absorption path can be made from measurements of experimentally determined profiles of single submillimetre-wave lines. At lower resolution the atmospheric absorption at 8 cm -1 attributed to dimers of the water molecule appears to have a doublet structure. The anomalous signal levels in the region of 22 and 28 cm -1 have been confirmed. A study of the sources of noise in the observations has shown that in a system using Golay cells, the dominant source of noise is the detectors, and that atmospheric modulation of the signal is, by comparison, negligible.