On the optical studies of the atmospheric water vapour from the surface of Mars

Remote observations of the atmospheric water vapour from the Mars orbit were usually carried out to study its global distribution and variability. Measurements of the water vapour abundance onboard the landers have recently become an important complement to the orbital sounding. Narrow-band filter photometry and spectroscopy of the solar radiation from the surface of the planet proved to be a powerful tool in the study of atmospheric water. The Imager for Mars Pathfinder (IMP) was the first instrument to measure its amount from the surface. The Surface Stereo Imager (SSI) onboard the Mars Polar Lander (MPL) was to follow but the spacecraft was lost at landing. Nevertheless significant expertise in the optical measurements of atmospheric H₂O was gained during these missions. This paper summarizes this experience emphasizing the radiative transfer aspects of the problem. The results of this study could be of importance for future missions to Mars.