Compact Polarimetry at the Moon: The Mini-RF Radars

The Mini-RF radar aboard India’s lunar Chandrayaan-1 satellite [1] (2008-9) was the first polarimetric synthetic aperture radar (SAR) outside of Earth orbit. The architecture of that radar—and of its more advanced two-frequency sibling on NASA’s Lunar Reconnaissance Orbiter [2] (2009)—is hybrid dual-polarimetric [3][4]. This architecture is a form of compact polarimetry [5] in which the dual-received data are orthogonal linear polarizations, in contrast to the transmitted polarization which is circular. The Mini-RF radars, as the pioneers for this new class of radar, illustrate the value of hybrid-polarity for lunar and planetary applications.