On the account of the Moon’s gravitational field in LEND measurements

Abstract

Space nuclear planetology experiments play significant role in the studies of planetary surface composition and volatiles distribution. To determine concentration of major rockforming elements and volatiles, one needs to perform model-dependent deconvolution and interpretation of experimental data. This model should completely simulate all environments and experimental conditions influencing neutron production and transport an also including finite lifetime of neutron. The existing Monte Carlo codes are extremely useful for complicated geometry simulations where time-dependent and wide-energy-range solutions are required. However, they usually do not include or include in very simplified way the gravitational field description appropriate for the simulation of neutron propagation on planetary scales. We have proposed an approach useful for surface-to-orbit transport simulations where neutron lifetime and planetary gravitational field are taken into account. The discussion how gravity force and finite neutron lifetime may influence the spectral and angular neutron distributions at different spacecraft altitudes is presented. The obtained results are implemented to the detection of hydrogen-bearing compounds in the lunar regolith. As a good example we used experimental data from LEND/LRO to evaluate how insertion of neutron finite lifetime and lunar gravitational field in numerical model of experiment may influence on the interpretation of measurements made by different LEND neutron detectors.