Solar Orbiter's Energetic Particle Detector (EPD)

Solar Orbiter is ESA's next heliospheric mission, foreseen for launch in early 2019. Solar Orbiter's primary science goal is to understand how the Sun creates and controls the heliosphere, this giant plasma bubble carved out of the interstellar medium by the supersonically expanding solar wind. ESA is providing the spacecraft, mission operations, and two facility instruments, SPICE and SIS, while the ESA member states provide most of the remaining payload. NASA provides the launcher, an Atlas V, and two instruments, Solo-HI, and SWA-HIS.

Solar Orbiter RGB


The Institute for Experimental and Applied Physics (IEAP) of the Christian-Albrechts-University (CAU) is developing four sensors for the Energetic Particle Detector (EPD), the Supra Thermal Electron and Proton (STEP) sensor, the Electron-Proton Telescope (EPT), the High-Energy Telescope (HET), and the Suprathermal Ion Spectrograph (SIS). The build and development of STEP, EPT, and HET is funded through the German space agency, DLR, and SIS is funded by ESA as a facility instrument.

Click me: a video to the project


The Energetic Particle Detector (EPD) suite consists of five sensors measuring electrons, protons, and ions from helium to iron, and operating at partly overlapping energy ranges from 2 keV up to 200 MeV/n. The EPD sensors and a common data processing unit with low voltage power supply are:

  1. SupraThermal Electrons and Protons (STEP)
  2. SupraThermal Ion Spectrograph(SIS)
  3. Electron Proton Telescope (EPT)
  4. High Energy Telescope (HET)
  5. Instrument Control Unit (ICU)
Functional Diagramm                                                          
Figure: EPD instrument functional diagramm.


The EPD sensors share the Instrument Control Unit (ICU) that is composed by the Common Data Processing Unit and the Low Voltage Power Supply (CDPU/LVPS), which is the sole power and data interface of EPD to the spacecraft.

STEP consists of a single unit having two view cones in opposite directions. SIS consists of two sensor heads with roughly opposite (160°) view directions sharing a common electronics box. EPT-HET has multiple view cones sharing a common electronics box. There are two identical EPT-HET units.

The overall energy coverage achieved with the EPD sensors is 0.002 MeV to 20 MeV for electrons, 0.003 MeV to 100 MeV for protons, 0.008 MeV/n to 200 MeV/n for heavy ions (species-dependent).


Energy Coverage

Figure: EPD energy coverage

FoV of EPD

Figure: FOV of the EPD sensors in the spacecraft reference frame. Background is colour coded as function of the probability of finding the interplanetary magnetic field (red/yellow higher than green/blue) by using the data from the HELIOS spacecraft.