The role of passive sounder packages on Spacelab

Satellite-borne passive sounders, either nadir sounders which point vertically downward or limb sounders which point towards the earth's limb, have so far been used for the measurement of temperature, water vapor and ozone in the atmosphere. The advantages and disadvantages of using passive sounders on Spacelab are reviewed and the instruments and the factors influencing their use (wavelength, source of radiation, field of view, and sensitivity) are discussed. The following instrument types are considered: filter photometer, filter radiometer, grating spectrometer, grille spectrometer, Fabry-Perot spectrometer, Michelson interferometer, gas correlation radiometer, heterodyne radiometer, microwave radiometer, polarimeter, albedometer, and TV system. The basic aims of a passive sounder package on Spacelab would be the determination of composition, temperature structure, and dynamics of the atmosphere over all heights and on a continuous global basis.