Solar Orbiter's Energetic Particle Detector (EPD)
SupraThermal Ion Spectrograph (SIS) identifies particles by time-of-flight (TOF) mass spectrometry, it will provide observations of He−Fe for an energy range from ~100 keV/nucleon up to 10 MeV/nucleon.
SIS consists of two telecopes, sunward and antisundward, located on a single electronic box with power and data interface to the ICU.
SIS is based on the ACE/ULEIS design which identifies particle species and energy by time-off-light by energy technique. Particles are detected when they pass through the entrance foils and deposit their energy in the solid state detector (SSD) at the back of the instrument. When the ion passes through the entrance, mid, and stop detectorfoils secondary electrons are emitted, accelerated to ~1 kV, and directed via isochronous mirrors onto microchannel plate stacks to provide a time-off-light measurement. The very high mass resolution of m/σm ~ 50 will allow SIS to measure particle populations with 3He/ 4He ratios down to <1%. SIS is now being developed under our European lead in collaboration with the Johns Hopkins University Applied Physics Laboratory (JHU/APL).
Figure: Schematic view of the SIS sensor
- SIS will determine the constituents and properties of the unexplored suprathermal ion pool within 1 AU
- SIS will provide the critical link between the energetic particles and the bulk solar wind measurements
- SIS will probe the energy range where differences in solar wind and energetic particle composition begin, in order to explore the reason for these differences
- Impulsive events will be detected primarily by SIS, since most produce particles of energy ~1 MeV/nucleon or less
- SIS will provide observational data for magnetic connection to reconnection sites low in the corona.
- SIS will provide the low energy SEP spectral segment required to identify 'breaks' in the large SEP event particle spectra observed by LET and HET
- SIS will provide high time resolution CME-shock associated energetic particle spectra close to or even within the acceleration site