The EPS, developed by Assurance Technology Corporation (ATC), (Formerly GE Panametrics
Corp.) in Carlisle, Massachusetts measures the energetic particles at geosynchronous orbit,
including protons, electrons, and alpha particles. The radiation in the environment consists of
particles trapped within the Earth’s magnetosphere as well as particles arriving directly from the
sun and cosmic rays that have been accelerated deep in space.

The sensors accurately measure the number of particles over a broad energy range and are the
basis for operational alerts and warnings of hazardous conditions. Energetic particles pose a risk
to satellites and to astronauts, and they can disrupt navigation and communications systems used
on the ground and in aircraft.

The Magnetospheric Electron Detector (MAGED) and Energetic Proton, Electron, and Alpha
Detector (EPEAD), two elements of the EPS, detect electrons over the energy range of 30,000
electron volts (30 keV) to greater than 4 million electron volts (4 MeV), in eight channels. The
Magnetosphere Proton Detector (MAGPD), EPEAD, and High Energy Proton and Alpha
Detector (HEPAD), which are additional EPS elements, detect protons over the energy range of
80 keV to greater than 700 MeV, in 16 channels. The EPEAD and HEPAD detect alpha particles
over the energy range 3.8 MeV to greater than 3,400 MeV, in eight channels.

The continuous long-term monitoring of the environment provided by these sensors forms the
basis for engineering guidelines for satellite design, for analyzing satellite failure and anomalous
behavior, for assessing the risk of human exposure to radiation, and for research leading to
improved models of the radiation environment. The sensors on the EPS have been expanded on
GOES-N,O,P to provide coverage over an extended energy range and with improved directional
accuracy.