Proceedings Article | 30 December 2004
Proc. SPIE. 5660, Instruments, Science, and Methods for Geospace and Planetary Remote Sensing
KEYWORDS: Radar, Calibration, Satellites, Synthetic aperture radar, Interferometry, Amplifiers, Interferometric synthetic aperture radar, Antennas, Space operations, Ka band
Topographic information is key to interpreting the geology and geophysics of planetary bodies such as the icy Galilean satellites. Traditionally elevation information has been derived from stereo-photogrammetry, but the last couple of decades have offered new techniques, including radar interferometry, photoclinometry (shape from shading) and laser altimetry. Combining synthetic aperture radar (SAR) technology with interferometry (InSAR) enables high resolution imaging with elevation information at each image point. With two appropriately spaced antennas on a spacecraft, single-pass imaging radar interferometry can provide wide swath topographic data, independent of solar illumination, as was recently demonstrated on Earth by the Shuttle Topographic Radar Mission (SRTM; www.jpl.nasa.gov/srtm). We will present the science requirements, measurement principle, a straw-man’s design, and the predicted performance of a “compact SRTM” which could be flown on NASA missions such as the proposed Jupiter Icy Moons Orbiter (JIMO). In this paper we discuss challenges, including the calibration strategy and critical technology elements such as the high power RF-amplifier. We expect that the performance, both in terms of elevation accuracy and mapping rate would suffice to 1) determine topography on local and regional scales; 2) search for active geological change on the time scale of JIMO’s orbit around, e.g., Europa (30-60 days); and 3) determine the global tidal amplitude at Europa, Callisto, and Ganymede, which would constitute direct proof of the existence of oceans in all three icy moons.
