The absolute magnetometers on board Swarm, lessons learned from more than two years in space

ESA's Swarm satellites carry 4He absolute magnetometers (ASM), designed by CEA-Léti and developed in partnership with CNES. These instruments are the first-ever space-borne magnetometers to use a common sensor to simultaneously deliver 1Hz independent absolute scalar and vector readings of the magnetic field. They have provided the very high accuracy scalar field data nominally required by the mission (for both science and calibration purposes, since each satellite also carries a low noise high frequency fluxgate magnetometer designed by DTU), but also very useful experimental absolute vector data. They have also been run for short periods of time in a so-called burst mode to deliver absolute scalar data at 250 Hz. In this presentation, we will report on the various tests and investigations carried out using these data since launch in November 2013. In particular, we will illustrate the advantages of flying ASM instruments on space-borne magnetic missions for data quality checks, geomagnetic field modeling and science objectives.