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Linear Energy Transfer Spectrometer (LETS)


Mission Name: Peregrine Mission 1 (Astrobotic)
Principal Investigator:Dr. Edward Semones


The Linear Energy Transfer Spectrometer (LETS) is a radiation sensor designed to study the lunar radiation environment. In particular, its objective is to measure the rate of incident radiation, both from galactic cosmic rays, and from solar events, to provide information on the hazards posed to astronauts. The LETS radiation sensor is a solid-state silicon Timepix detector. This comprises a pixellated semiconductor sensor connected to a signal processing ASIC (Application Specific Integrated Circuit). The Timepix detector is 1.4 x 1.4 cm chip with an array of 256 x 256 silicon pixels covering a total area of 2 square cm. Each pixel is 55 x 55 microns and 500 microns thick. The sensor can cover a dynamic energy range from 5 keV photons to heavy ions with energies greater than 2 GeV. The sensor is connected to an electronics processing chain on the LETS board consisting of a preamplifier, discriminator, and counter. A timer is used to convert the time the pixel sensor is over its threshold detection value to the energy deposit in the pixel. LETS also has heaters, a heater control board, 28 V DC/DC converter, and an electromagnetic interference filter. The detector is mounted on the top deck of Peregrine above one of the landing legs. It will send data back over the lifetime of the mission at a one minute cadence, in addition to sending cruise data on an hourly basis.

Alternate Names

  • PeregrineMission1/LinearEnergyTransferSpectrometer(LETS)


  • Planetary Science: Fields and Particles

Additional Information

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



NameRoleOriginal AffiliationE-mail
Dr. Edward SemonesPrincipal InvestigatorNASA Johnson Space
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