User:Steve Quinn/Cosmic Ray Telescope for the Effects of Radiation

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO) characterizes the radiation environment that will be experienced by humans during future lunar missions. The unprotected lunar environment bathes in solar plasma and space weather. Therefore, CRaTER measures the debilitating effects of radiation (ionizing energy) to matter due to energetic protons, helium ions, and HZE ions, that penetrate materials and skin tissue. This radiation travels through interplanetary space, believed to be carried by the shocks associated with coronal mass ejections, and is a source of space weather. The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument is designed to characterize the global lunar radiation environment and its biological impacts.

Determining survivability
Two forms of radiation pose potential health risks to astronauts in deep space. One is galactic cosmic rays, particles generated by supernova explosions and other high-energy events outside the solar system. The other is solar energetic protons (SEP) associated with solar flares and coronal mass ejections from the sun.

Measurements are specifically enabled with onboard sensors that are silicon - solid-state detectors, and after radiation interactions with this equipment, tissue equivalent plastic (TEP), a synthetic analog of human tissue. CRaTER computes and quantifies how much radiation is imparted to either electronic equipment or human tissue by a process known as linear energy transfer. This is accomplished in tandem with direct measurements with the lunar space radiation environment, particularly the interactions of ions with energies above 10 MeV, which penetrate and are detected by CRaTER.

Combined with models of radiation transport through materials, CRaTER LET measurements set limits on allowable ionizing radiation levels in the lunar environment for biological organisms by combining with computer models  of radiation transport through materials. It also provides valuable information on radiation effects on electronic systems operating in and deep space.

Physical lunar environment
In addition to these (above) human exploration goals, CRaTER measurements also provide new insights on the spatial and temporal variability of the SEP and GCR populations and their interactions with the lunar surface.