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P.N. Mohammed, P.G. Steffes (Georgia Inst. of Tech.)
A model has been developed for the centimeter-wavelength opacity of phosphine (PH3), which provides an order of magnitude improvement over previous models (Hoffman et al. Icarus 152, 172-184, 2001). A laboratory measurement program is now in progress to verify and refine this model at low pressures and temperatures, and at higher frequencies. The opacity of PH3 in a hydrogen/helium (H2/He) atmosphere has been measured at frequencies in the Ka band region at 32.7 GHz (9.2 mm), 35.6 GHz (8.4 mm), 37.7 GHz (8.0 mm) and 39.9 GHz (7.5 mm) at pressures of 0.5, 1 and 2 bars and at a temperature of 293 K. Further experiments will be conducted at temperatures of 213 K and 173 K at the same frequencies and pressures. These measurements will elucidate the interpretation of millimeter wavelength observations from radio telescopes as well as radio scientific studies conducted by Cassini at Saturn at the downlink frequency of 32 GHz (9.4 mm).
This work is supported by the NASA Planetary Atmospheres Program under grant NAG5-4190.
The author(s) of this abstract have provided an email address for comments about the abstract: gt4863a@prism.gatech.edu