A Doppler filter technique to measure the hydrogen content of planetary surfaces

Abstract

A new technique to measure the hydrogen content of planetary surfaces is suggested. It relies on the Doppler energy shift of planetary albedo neutrons in the frame of a planar neutron sensor aboard a low-altitude orbiting spacecraft. It can be realized by a small modification to the current design of the anticoincidence shield enclosing a possible Mars Observer gamma-ray spectrometer. The resultant sensitivity to hydrogen near the surface of the Moon is estimated to be nearly three orders of magnitude greater than the sensitivity inherent in the detection of 2.223 MeV neutron capture γ-rays by the spectrometer.