Planetary Radar Astronomy
by Jean-Luc Margot (UCLA)
Planetary Radar Astronomy is the study of solar system bodies by means of Earth-based radar telescopes. It is a field in which the experimenter controls the direction, amplitude, frequency, phase, polarization, and time/frequency structure of the transmitted waveform. Analysis of radar echoes yields information on range, velocity, spin, reflectivity, and polarization properties of the target. Range and velocity measurements with fractional precisions of 10e-8 enable tests of physical theories, detection of minute non-gravitational effects, and dramatic improvements in asteroid trajectory predictions. Spin measurements with fractional precisions of 10e-5 probe planetary interior structure and processes, including moments of inertia (Mercury), angular momentum exchange (Venus), and icy shell properties (Europa, Ganymede). Reflectivity measurements with <10 m spatial resolutions provide detailed terrain maps and superb characterization of near-Earth asteroids, including binary and triple systems. Polarization data reveal information about near-surface roughness and composition. I will provide an overview of recent accomplishments and future prospects, highlighting possibilities for the GBT.
