The Magnetometer measures the magnitude and direction of the Earth's ambient magnetic field with three orthogonal sensors, located in a sensor assembly and attached to a boom that places the sensor three meters away from the body of the spacecraft.
The EPS and HEPAD monitor solar protons and alpha particles, produced during large flares, which are a radiation hazard to manned and unmanned operations in space and the ionosphere at high latitudes. The HEPAD instrument covers the very high-energy protons and alpha particles that are produced in large solar flares.
The XRS performs real-time measurements of the solar X-ray emissions in two channels covering the spectral ranges of 0.5 to 3 Angstroms (shortwave) and 1 to 8 Angstroms (longwave). The sensitivity of the sensor was chosen to permit quiet sun background measurements at as low a level of solar activity as possible while detecting events at the lowest practicable threshold for early event warning.