CRaTER Galactic Cosmic Ray (GCR) Linear Energy Transfer (LET) Spectra

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) has been in orbit around the Moon aboard NASA's Lunar Reconnaissance Orbiter (LRO) since 2009. Its primary observations have been of the slowly-varying flux of galactic cosmic rays (GCRs) arriving from interplanetary space, which are modulated by solar activity. This dataset presents the Linear Energy Transfer (LET) spectra of the cosmic rays, as measured when the sensor was facing straight up away from the lunar surface and during periods when solar energetic particle activity is quiet, from the spacecraft's arrival at the Moon until the present day. These LET spectra quantify the energy deposit (radiation dose) behind 9.9 g/cm^2 of shielding, mostly consisting of Tissue-Equivalent Plastic (TEP). This is an ongoing dataset, and will be updated with another measurement of the LET spectrum every six months. Plots of the variations of these measurements over the mission are shown, and will also be updated every six months, in the accompanying descriptive README file.