CRaTER: The Cosmic Ray Telescope for the Effects of Radiation Experiment on the Lunar Reconnaissance Orbiter Mission

Abstract

The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO) characterizes the radiation environment to be experienced by humans during future lunar missions. CRaTER measures the effects of ionizing energy loss in matter due to penetrating solar energetic protons (SEP) and galactic cosmic rays (GCR), specifically in silicon solid-state detectors and after interactions with tissueequivalent plastic (TEP), a synthetic analog of human tissue. The CRaTER investigation H.E. Spence et al.quantifies the linear energy transfer (LET) spectrum in these materials through 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 constrain models of the biological effects of ionizing radiation in the lunar environment as well as provide valuable information on radiation effects on electronic systems in deep space. In addition to these 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. We present here an overview of the CRaTER science goals and investigation, including: an instrument description; observation strategies; instrument testing, characterization, and calibration; and data analysis, interpretation, and modeling plans.

The deep space galactic cosmic ray lineal energy spectrum at solar minimum

“…[35] The most precise published calibration of the CRaTER detection electronics took place on the ground before launch using a combination of energetic particles from a proton beam and alpha particles from a radioactive Americium-241 source [Spence et al, 2010]. The calibration process calculates the needed coefficients to convert from analog-digital units (ADU) to the physical units of lineal energy.…”

The Relativistic Proton Spectrometer (RPS) for the Radiation Belt Storm Probes Mission

“…We suppressed internal reflections of light from backwards-going protons by painting the topmost surface of the radiator with a space qualified conducting black paint. A springloaded assembly holds the radiator in place; we used this method of pre-loading to mount detectors in the LRO/CRaTER instrument (Spence et al 2010) and it proved itself useful for RPS. Here the primary concern was possible mechanical damage to the radiator crystal in the vibroacoustic launch environment.…”

Near‐Real‐Time Situational Awareness of Space Radiation Hazards

“…Large SEP events on 23 January 2012, on 27 March 2012, and in the summer of 2012 contributed significantly to the hazards of the space environment over this interval. We observe that the dose rate limit of 200 centigrays for the lens dose [Cucinotta et al, 2010] is exceeded for nominal spacecraft shielding.Among the satellite measurements used by PREDICCS are data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on NASA's Lunar Reconnaissance Orbiter [Spence et al, 2010]. For the SEP events of 23 January (Figure 1 Figure 1.…”

“…Among the satellite measurements used by PREDICCS are data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on NASA's Lunar Reconnaissance Orbiter [Spence et al, 2010]. For the SEP events of 23 January (Figure 1 Figure 1.…”

“…Among the satellite measurements used by PREDICCS are data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument on NASA's Lunar Reconnaissance Orbiter [Spence et al, 2010]. For the SEP events of 23 January (Figure 1 validation that PREDICCS models are accurate but also directly measures the biological impacts of radiation by observing linear energy transfer spectra behind different thicknesses of tissue-equivalent plastic [Spence et al, 2010].…”