View Instrument

These spacecraft each feature dual flux-gate magnetometers on a 8.5 meter long boom. The magnetometers are provided by Science Applications International Corporation (SAIC), Inc. in Columbia, Maryland. They measure the magnitude and direction of the Earth's geomagnetic field, detect variations in the magnetic field near the spacecraft, provide alerts of solar wind shocks or sudden impulses that impact the magnetosphere, and assess the level of geomagnetic activity. One magnetometer sensor is mounted on the end of the boom 27.9 feet (8.5 m) from the spacecraft. The other is positioned on the same boom 2.6 feet (0.8 m) closer to the spacecraft. The second magnetometer sensor serves as a backup in case the first magnetometer sensor fails and provides for better calibration of the magnetometer data channel. The two magnetometers can operate independently and simultaneously. Each magnetometer features three orthogonal elements that provide magnetic field measurements in three mutually perpendicular components: HP, HE and HN. HP is perpendicular to the satellite's orbital plane. HE lies parallel to the satellite-Earth center line and points earthward. HN is perpendicular to both HP and HE, and points eastward.