Relativistic Proton Spectrometer (RPS)
The RPS will measure inner Van Allen belt protons with energies from 50 MeV to 2 GeV. Presently, the intensity of trapped protons with energies beyond about 150 MeV is not well known and thought to be underestimated in existing specification models. Such protons are known to pose a number of hazards to astronauts and spacecraft, including total ionizing dose, displacement damage, single event effects, and nuclear activation. This instrument will address a priority highly ranked by the scientific and technical community and will extend the measurement capability of this mission to a range beyond that originally planned. The project’s goal is development of a new standard radiation model for spacecraft design.
RPS Science Investigation Objectives:
- Support development of a new AP9/AE9 standard radiation model for spacecraft design
- AFRL to develop and test model for Van Allen Probes data in general and RPS specifically
- AP9 (protons) and AE9 (electrons) will provide standardized worst-case specifications: dose rate; internal charging/deep dielectric charging; surface charging (most intense fluxes in keV electrons)
Answer the following science questions:
- How do solar energetic particle (SEP) events, large magnetic storms, and shocks/sudden commencements modify the Inner Belt?
- What, in addition to cosmic ray albedo neutron decay (CRAND), determines the steady-state inner belt?
- How does the inner belt decay during geomagnetic quiet time
Relativistic Proton Spectrometer
RPS measures energy spectra and angular distributions of protons from 50 MeV to 2 GeV (expect full inner-zone spatial distributions with better-than-weekly cadence)
-Energetic protons responsible for total dose in MEO for shielding thickness over 200 mils aluminum
-Protons responsible for displacement damage
Telescope consists of 8 silicon detectors and a Cherenkov detector
-Stacked Si detectors used for 50 MeV to ~400 MeV, incident angle constrained by 8-fold coincidence
-Chenrenkov detector used for >400 MeV
-Absolute flux accuracy: dJ/J ~10%
-Energy resolution: dE/E ~30% @ 50 MeV, to 100% @ 2 GeV
-Angular resolution: 30° instantaneous, 5°deconvolved