Radiation Assessment Detector (RAD)
PI: Donald Hassler, Southwest Research Institute
The Radiation Assessment Detector (RAD) is an energetic particle analyzer designed to characterize the full spectrum of energetic particle radiation at the surface of Mars, including galactic cosmic rays (GCRs), solar energetic particles (SEPs), secondary neutrons and other particles created both in the atmosphere and in the Martian regolith.
The RAD instrument consists of a charged particle telescope comprised of three solid-state detectors and a cesium iodide (CsI) calorimeter. An additional BC-432 scintillating plastic channel is used together with the CsI calorimeter and an anti-anticoincidence shield to detect and characterize neutral particles (i.e., neutrons and gamma rays). The outputs of the various photodiodes, used with the CsI and scintillating plastic, and solid-state detectors are converted to digital pulse height discriminated signals for further processing. The digital logic includes an embedded microcontroller to bin and format the data. The RAD particle and energy coverage is shown in the figure below. The RAD instrument is mounted just below the top deck of the rover with the charged particle telescope pointed in the zenith direction.
Photo of RAD flight model in the lab (left) and artwork of an older MSL rover design, showing RAD charged particle channel 65-degree field-of-view pointing towards the zenith.
The RAD instrument will be used throughout the mission, including part of the cruise phase, to characterize the radiation environment of MSL. It is desirable for the instrument to be powered continuously while on the Martian surface. However, because of rover energy constraints, the present plan is to acquire roughly 15-minute observations every hour throughout each sol.
RAD's primary science objectives are to:
- Characterize the energetic particle spectrum at the surface of Mars
- Determine the radiation dose for humans on the surface of Mars
- Enable validation of Mars atmospheric transmission models and radiation transport codes
- Provide input to the determination of the radiation hazard and mutagenic influences to life, past and present, at and beneath the Martian surface
- Provide input to the determination of the chemical and isotopic effects of energetic particles on the Martian surface and atmosphere
RAD energy coverage for both charged and neutral particles.