CHARACTERIZATION OF THE THERMODYNAMIC BEHAVIOR OF PRESSURE MODULATED CELLS FOR REMOTE-SENSING OF THE ATMOSPHERE OF MARS

A radiometric experiment was conducted to investigate the thermodynami c behaviour of the H2O and CO2 pressure modulated cells of the Pressur e Modulator Infrared Radiometer (PMIRR) which flew on ''Mars Observer' ' in 1992. The wave forms and phases of the transmission, emission, pr essure and piston position cycles. together with the mean absorption w ere, for the first time, all measured during the same experiment. The measured transmission and emission cycles were used to calculate the p hase and amplitude of the temperature cycles and were found to be supe r-adiabatic for both cells, in reasonable agreement with a thermal dif fusion model. Anomalies were seen in the H2O modulator driving frequen cy, as has been observed by other authors. but none were evident in th e measured cell wave forms suggesting that the water vapour behaves as an ideal gas in the cell.