The primary goal of CRaTER is to characterize the global lunar radiation environment and its biological impacts. This objective is critical if we are to implement a sustained, safe, and affordable human and robotic program to search for evidence of life, understand the history of the solar system, and prepare for future human exploration, a vision established by the President's Space Exploration Policy Directive.

In order to achieve this high-priority objective, the CRaTER investigation team established the following interrelated investigation goals:

1. Measure and characterize that aspect of the deep space radiation environment, LET spectra of galactic and solar cosmic rays (particularly above 10 MeV), most critically important to the engineering and modeling communities to assure safe, long-term, human presence in space.
   
2. Develop a novel instrument, steeped in flight heritage, that is simple, compact, and comparatively low-cost, but with a sufficiently large geometric factor needed to measure LET spectra and its time variation, globally, in the lunar orbit.
   
3. Investigate the effects of shielding by measuring LET spectra behind different amounts and types of areal density, including tissue-equivalent plastic.
4. Test models of radiation effects and shielding by verifying/validating model predictions of LET spectra with LRO measurements, using high-quality GCR and SPE spectra available contemporaneously on ongoing/planned NASA.