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Energetic Particle Detector (EPD)

NSSDCA ID: 2020-010A-07

Mission Name: Solar Orbiter
Principal Investigator:Dr. Javier Rodríguez-Pacheco Martin


The Energetic Particle Detector (EPD) on Solar Orbiter comprises a suite of four sensor types designed to make in-situ measurements of the spectra, composition, time variation, and directional distribution of energetic particles over an energy range of 2 keV to 500 MeV/n. The main science objective of EPD is to study how solar eruptions produce energetic particle radiation that fills the heliosphere. This can be broken into three studies: 1)How and where energetic particles are injected at the sources and, in particular, what the seed populations are for energetic particles; 2) How and where energetic particles are accelerated at the Sun and in the interplanetary medium; and 3) How energetic particles are released from their sources and distributed in space and time.

The EPD suite is composed of the SupraThermal Electrons andProtons (STEP) sensor; the Suprathermal Ion Spectrograph(SIS); the Electron Proton Telescopes (EPT); and the HighEnergy Telescopes (HET). The overall mass of the suite is 15.718 kg, including the Instrument Control Unit (ICU), intraharness, and multilayer insulator. Total power used is 19.7 W. An additional 16.36 W is required for the survival heaters.

The STEP sensor is mounted on the side of the spacecraft bus. It has a mass of 1.998 kg and uses 2.9 W power. It measures count rates of electrons and ions in the energy range from 2 to 80 keV. The field-of-view is 28 x 54 degrees, divided into 15 sectors. The geometric factor is 0.008 square cm per steradian, time resolution is 1 second.

The SIS sensor is mounted on top of the spacecraft bus. It hs a mass of 6.816 kg and uses 3.8 W power. It covers the energy range from 14 keV/n to 20.5 MeV/n, and measures count rates for major solar species such as H, 3He, 4He, C, N, O, Ne, Mg, Si, S, Ca, and Fe. It has two 22 degree fields-of-view, one sunward and one anti-sunward. The geometric factor is 0.2 square cm per steradian, time resolution is 3 seconds.

The EPT and HET instruments each have two sensors, one of each sensor is colocated, the two sets on opposite sides of the spacecraft bus and designated EPT-HET1 and EPT-HET2. EPT-HET1 has a mass of 1.565 kg and uses 4.4 W, EPT-HET2 has a mass of 1.566 kg and uses 4.6 W. The EPT studies electrons, H, and He in the energy range 25-475 keV (electrons); 25 keV-6.4 MeV (H); and 1.6-6.4 MeV (He). It has four 30 degree fields-of-view: sunward, anti-sunward, north, and south. The geometric factor is 0.01 square cm per steradian, time resolution is 1 second.

HET observes electrons and major solar species (H, 3He, 4He, C, H, O, Ne, Mg, Si, S, Ar, Ca, Fe, Ni). The energy range for electrons is 0.3-30 MeV. The energy range for other species can vary from 6.8-500 MeV/n. It has four 43 degree fields-of-view (sunward, anti-sunward, north, and south). The geometric factor is 0.27 square cm per steradian and the time resolution is 1 second.

For more information on EPD, see:

Alternate Names

  • SolarOrbiter/EnergeticParticleDetector(EPD)

Facts in Brief

Mass: 15.718 kg
Power (avg): 19.7 W


  • Solar Physics: None assigned
  • Space Physics: Heliospheric Studies

Additional Information

Questions and comments about this experiment can be directed to: Coordinated Request and User Support Office



NameRoleOriginal AffiliationE-mail
Dr. Javier Rodríguez-Pacheco MartinPrincipal
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