opened the way for compact, efficient, high-power laser systems and advances in composite material and other receiver technologies permitting the development of large-area, lightweight receiver systems.

Present and planned space-based ozone sensors provide global coverage, but with relatively sparse sampling, i.e., a return time of typically 3 to 7 days on a given tract. This is a significant limitation, considering the large variability of concentrations at extratropical latitudes and in the troposphere. Measurements on a geostationary orbit would provide continuous data over spatial scenes representing one-third of a hemisphere. Nadir observation of O₃, CO, and H₂O with ~2 km vertical resolution down to the surface could be achieved in a geostationary orbit with a Fourier transform spectrometer or a gas-correlation spectrometer.

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