The research reported in this paper was motivated by a Global Positioning System (GPS) data set collected by researchers at The Johns Hopkins University, Applied Physics Laboratory (JHU/APL) in May 1999. Raw GPS signal data were collected from an aircraft equipped with two down-looking antennas for receiving both left-hand circularly-polarized (LHCP) and right-hand circularly-polarized (RHCP) GPS reflections from the ocean surface. Concurrent measurements of the local wind and wave conditions were collected from a nearby research vessel. The measured (LHCP) waveforms were similar to those already reported by [1]. The reflected RHCP waveforms were about 10 dB below those from the LHCP antenna. As far as we know, detection of the (depolarized) RHCP waveform has not been previously demonstrated. Models for GPS surface scattering based on geometrical optics or the Kirchhoff approximation predict a very weak depolarized return.
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