Abstract
The near-Earth energetic particle environment has been monitored since the 1970’s. With the increasing importance of quantifying the radiation risk for, e.g. for the human exploration of the Moon and Mars, it is essential to continue and further improve these measurements. The Electron Proton Helium INstrument (EPHIN) on-board SOHO continually provides these data sets to the solar science and space weather communities since 1995. Here, we introduce the numerous data products developed over the years and present space weather related applications. Important design features that have led to EPHINs success as well as lessons learned and possible improvements to the instrument are also discussed with respect to the next generation of particle detectors.
Highlights
SEP, from suprathermal up to relativistic energies are an important contributor to the space environment characterization
Besides software updates and performance studies based on historical data that have not been used in the calculation of the forecasting matrix, the HESPERIA Relativistic Electron Alert System for Exploration (REleASE) scheme has been developed such that its innovation is to enable derivation and provision of the 30–50 MeV proton forecast based on electron measurements from ACE/EPAM (Gold et al, 1998) as well as Electron Proton Helium INstrument (EPHIN)
Providing 25 years of continuous measurements during two entire solar cycles and a variety of different solar activities resulting in different SEP environments, EPHIN on-board SOHO is a valuable asset regarding particle detection for the space weather and solar science communities
Summary
SEP, from suprathermal (few keV) up to relativistic (few GeV for protons and ions) energies are an important contributor to the space environment characterization. In-between both half-orbits (around the time of the roll maneuver), a short period during which communication is limited remains. These keyhole periods are the reason for the majority of EPHIN’s data gaps. The failure modes remove the defective detectors from the coincidence logic which results in lower number of energy channels per particle type (four in nominal mode, three and two for FME and FMD, respectively) It was possible, to retrieve the nominal energy channels based on the energy losses in the SSD A, B and C using PHA data A summary concludes the importance of measurements from EPHIN for the space weather community and proposes design features for future instruments
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