Retrieval of atmospheric temperatures in the Martian planetary boundary layer using upward-looking infrared spectra

We present an algorithm for the retrieval of temperature in the planetary boundary layer (lowest few kilometers) of the martian atmosphere using upward-looking infrared spectra from a Mars lander. Temperature profiles retrieved from an orbiting or passing spacecraft do not have adequate vertical resolution to provide significant information within the planetary boundary layer. By using spectra taken from a surface lander looking upward toward zenith, and by transforming to a vertical coordinate that ''stretches out'' the atmosphere just above the surface where the contribution to the observed radiation peaks, we find that an efficient algorithm can be formulated with adequate vertical resolution to successfully retrieve temperature profiles that exhibit the major features of the diurnal cycle of planetary boundary layer temperatures. We expect that this technique can be extended to simultaneously retrieve the opacity, and possibly the scattering properties, of atmospheric aerosols as well. Although no upward-looking martian infrared spectra yet exist, demonstration of the abilities of a lander-based infrared spectrometer is important for the planning of future missions to Mars. (C) 1996 Academic Press, Inc.