Measurements in the atmosphere of Mars.

The detailed definition of the key features of Mars' atmosphere from one or a few entries and landings is a challenging task involving a variety of measurements, taken during entry and after landing, and correlated with observations to be taken from orbiters and flyby missions. The properties of interest include profiles to high altitudes of the atmospheric state properties, composition (abundant gases and minor constituents related to life processes), and meteorological factors such as winds, clouds, and variations in pressure and temperature. Profiles of the atmosphere are best measured during entry, by techniques which are described. The lander, if designed for lifetimes of days to weeks, can contribute information on diurnal variability of the atmosphere, and possibly on clouds and winds. Landings at several latitudes and in different seasonal regions will probably be required to complete a first order description of the atmosphere.