Remote Sensing of Earth and Planetary Atmospheres Using Gas Correlation Spectroradiometry

Abstract

Gas correlation spectroradiometry is one of the most frequently used techniques for remote measurements of atmospheric properties. It is a relatively simple and robust technique which is most useful in applications where very high spectral discrimination (up to the line Doppler width) is required and yet signal levels are low. Such is the case for Earth upper atmospheric temperature and species abundance measurements and for numerous planetary measurement objectives. The first spaceborne gas correlation experiment (Abel et al 1970) was flown on Nimbus 4 by Oxford University to obtain global measurements of stratospheric temperature. Since the launch of that instrument in 1970, eight Earth orbital instruments and one planetary experiment have used this technique for a variety of atmospheric investigations. Gas correlation spectroradiometry continues to offer significant advantages over other instrumental approaches for investigations in which instrument capability and complexity are equally important considerations. For example, the atmospheric sounder now being developed at JPL for the Mars Observer planetary mission (McCleese et al 1986) uses gas correlation spectral channels to achieve a resolution of 0.01 cm–1 in the mid-infrared using hardware of minimum complexity and having substantial flight heritage.