Charged Particle Spectrometer
Outline of Instrument

Charged Particle Spectrometer (CPS)

The ARD will detect alpha rays emitted by Rn and Po on the lunar surface for identification of gas emanation and obtaining information on the crustal movement during the last - 50 years.
The PS will observe solar and galactic cosmic rays around moon. That is due to protecting human health in the space from radiation particles and to obtain basic cosmic rays data around moon for forecast of cosmic ray radiations in the space.


The ARD and the PS instruments consist of Si semiconductor detectors with high energy resolution. An incident particle is identified by the method of delta-E by total-E using the information of energy deposited in multilayer Si detectors respectively. We obtain not only energy information but also element information for the incident cosmic ray.

Principle of Observation
  1. Neutrons are produced in the lunar subsurface by irradiation of Galactic Cosmic Ray.
  2. Gamma rays with the energy characteristic to each element on the Moon are produced by interactions of those neutrons with surface elements. Natural radioisotopes also emit gamma rays.
  3. Elemental composition is determined by measuring the gamma-ray energies from the lunar orbit.
Principle of Observation

Results Expected
Simulation image of observation by ARD
Simulation image of observation by ARD
We can investigate time variation of the gas emanation with the time scale between one month and one year during the mission period as well as with the time scale of years through direct comparison with the previous missions using the ARD instrument. We will obtain basic cosmic rays data around moon for forecast of cosmic ray radiations in the space by the PS instrument.

PI Introduction
CPS Takeshi Takashima

Takeshi Takashima

Department of Space Plasma Physics,