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B.J. Butler (NRAO), J.M. Jenkins (SETI Institute), P.G. Steffes (Georgia Institute of Technology)
Aside from narrow windows in the infrared portion of the spectrum, radio wavelengths are unique in their ability to probe through the thick atmosphere of Venus to the surface. By varying the radio wavelength used to observe Venus, different levels in the atmosphere may also be probed. Such observations may then be used to constrain the possible conditions at the surface (temperature and dielectric constant) and in the atmosphere (temperature and gas abundance vertical profiles) of the planet.
Observations of Venus at radio wavelengths have been obtained using the Very Large Array (VLA) in New Mexico . The VLA has a large effective collecting area, and spans a large portion of the radio wavelength spectrum, making it a powerful instrument for such observations. The VLA has been used to observe Venus from wavelengths as short as 7 mm to as long as 20 cm. Comparison of these data with detailed models of the surface and atmospheric emission from Venus show a good match at the shorter wavelengths (\lambda < 3 cm). However, at longer wavelengths (\lambda > 3 cm), the observed brightness temperature is larger than predicted by models with what would seem reasonable parameters. The discrepancy could be explained if those seemingly reasonable parameters were not so reasonable, or if there is a problem with the calibration scale at the VLA at these longer wavelengths. Neither of these explanations seems particularly likely, however. These and possible alternative explanations will be presented and discussed.
The author(s) of this abstract have provided an email address for comments about the abstract: bbutler@planets.aoc.nrao.edu