MEASURING PLANETARY NEUTRON ALBEDO FLUXES BY REMOTE GAMMA-RAY SENSING.

A remote-sensing gamma -ray spectrometer (GRS) is capable of measuring planetary surface composition through the detection of characteristic gamma rays. In addition, the planetary neutron leakage flux may be detected by means of a thin neutron absorber surrounding the gamma -ray detector which converts the neutron flux into a gamma -ray flux having a unique energy signature. The gamma rays representing the neutron flux are observed against interference consisting of cosmic gamma rays, planetary continuum and line emission, and a variety of gamma rays arising from cosmic-ray particle interactions with the gamma -ray spectrometer and spacecraft (SC). In this paper the amplitudes of planetary and non-planetary neutron fluxes are assessed and their impact on the sensitivity of measurement is calculated for a lunar orbiter mission and a comet nucleus rendezvous mission.