The magnetometer system is a simplified version of the magnetometers flown on Mars Global Surveyor and Lunar Prospector.
It is a tri-axial flux gate design that will be mounted on the STEREO ~4m boom just inboard of the SWEA and STE instruments.
The flux gate sensors use a ring core geometry, with magnetic cores consisting of molybdenum alloy.
The units are compact, low power, and ultra-stable.

    To optimize sensitivity at the low field values to be found in interplanetary space, the magnetometer dynamic range is divided into 8 
    ranges that are automatically switched whenever the field being measured exceeds a predetermined level. 
    The maximum range is sufficiently large to allow IMPACT MAG magnetic field measurements during the commissioning phase Earth orbits.