Dr. Muhleman will make observations of Mercury, Venus, Mars, Saturn, and Titan at centimeter and millimeter wavelengths using a number of different telescopes and observing techniques. The experiments are designed to measure and interpret processes that can not be studied with existing spacecraft or in other wavelength bands. The program includes the investigation of the middle and upper atmospheric wind systems on Venus and Mars using the various rotational transitions of carbon monoxide as the tracer gas. Mercury, Mars, Saturn's rings, Titan, and Venus will be studied with the new technique of using the Very Large Array telescope as a synthetic aperture radar receiver of echoes from these objects that are illuminated by the Goldstone radar transmitter. Such radar images provide powerful tools for investigation of the subsurface structures of the terrestrial planets and the rings of Saturn. Radio wavelength techniques offer unique capabilities in planetary science. They can be employed to probe down to the 100-bar level in the atmospheres of the major planets, whereas no spacecraft experiment to date has measured anything deeper than 2 bars, and that includes the Galileo mission to Jupiter. Similarly, no spacecraft experiment has sampled any planetary surface deeper than 1 or 2 cm. An additional unique role for Earth-based radio techniques is for synodic studies of the planets over timescales of several years. Dr. Muhleman uses state of the art Earth-based radio astronomy facilities and techniques to probe the surfaces of planets and the physics of their atmospheres.
