Cosmic gamma-ray spectrometer with tagged charged particles of Galactic Cosmic Rays

A new concept is proposed for the study of the elemental composition of planetary surfaces on landed missions through the coincident detection of gamma rays induced by Galactic Cosmic Ray (GCR) charged particles and the detection of the incident charged particle that produces the gamma ray. Charged particle detection is used to tag all instances of GCR interaction in a selected volume of the subsurface that results in the emission of secondary gamma rays. Using the criteria of a tagged GCR particle and coincident gamma ray detection, one may measure gamma ray spectra produced in a selected subsurface volume by GCR induced spallation and inelastic scattering of fast neutrons. The proposed new technique minimizes the contribution of gamma radiation from other regions of the subsurface and spacecraft structural components that may add background to the measured gamma-ray spectrum from the selected soil volume.