A 10 micron laser heterodyne spectrometer for remote detection of trace gases

Infrared heterodyne spectroscopy provides a means of measuring the intensity profiles of individual rotation-vibration spectral lines with high sensitivity. Considerable effort has been expended on optimizing these instruments for remote measurements of gases in planetary atmospheres with the result that present-generation spectrometers are beginning to provide new and startling results on the planets. The fundamental principles of laser heterodyne spectroscopy are discussed. Detailed considerations of the optical design and the electronic design of the spectral-line receiver are given. Representative results obtained with this spectrometer are discussed, including precision frequency measurements of NH3 (nu-2) lines, detection of auroral emission from Jupiter, and measurements of terrestrial O3 and CO2.