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Cosmic Ray Telescope for the Effects of Radiation (CRaTER)

NSSDCA ID: 2009-031A-06

Mission Name: Lunar Reconnaissance Orbiter (LRO)
Principal Investigator:Dr. Harlan E. Spence


The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) is designed to characterize the lunar radiation environment and its biological impacts. The instrument comprises tissue-equivalent plastic and silicon detectors to determine the effects of radiation on human tissue. The primary goals are to measure the spectra of galactic and solar cosmic rays most critically important to the engineering and modeling communities to assure safe, long-term human presence in space and to investigate the effects of shielding by measuring spectra behind different types and amounts of areal density.

The CRaTER instrument is a stacked detector cosmic ray telescope consisting of 6 ion-implant silicon linear energy transfer (LET) detectors and 2 sections of tissue equivalent plastic (TEP). The telescope is cylindrical in shape and views in two directions, with a circular 75 degree field of view downwards (nadir, towards the Moon) and a 35 degree field of view upwards. There are two types of detectors used, 3 low LET detectors which are 1000 microns thick and has an energy threshold of 0.2 MeV and 3 high LET detectors, 140 microns thick with a threshold of 2 MeV. The detectors are all circular with a diameter of 3.5 cm. The detectors are arranged in 3 pairs, with the low LET detector on top of the high LET detector. One pair is at each entrance aperture and one is between the two layers of TEP. The top layer of TEP is a 5.4 cm thick cylinder and the bottom layer is 2.7 cm thick. The TEP, detectors, and apertures are arranged so that any particle entering the nadir aperture will pass through at least the entrance detector, the bottom layer of TEP, and the center detector, and through the upper aperture all three detectors so the absorption of the TEP can be ascertained. The A-150 TEP is designed to be analogous to human muscle and is 77.5% carbon and 10.1% hydrogen by weight. The charge is collected in each detector and the signal is sent to on-board analog and digital processing electronics.

Alternate Names

  • CRaTER
  • urn:nasa:pds:context:instrument:lro.crat

Facts in Brief

Mass: 5.6 kg
Power (avg): 9 W
Bit rate (avg): 89.4 kbps

Funding Agency

  • NASA-Office of Space Science Applications (United States)


  • Planetary Science: None assigned
  • Life Science: None assigned

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Harlan E. SpencePrincipal InvestigatorBoston

Selected References

  • Spence, H. E., et al., CRaTER: The Cosmic Ray Telescope for the Effects of Radiation Experiment on the Lunar Reconnaissance Orbiter Mission, Space Sci. Rev., 150, 243-284, doi:10.1007/s11214-009-9584-8, 2010,
CRaTER Project Home Page - University of New Hampshire

[LRO CRaTER diagram]

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