Daily Calibration of the Fluxgate Magnetometer Onboard the Cluster Spacecraft

Abstract During their 24 years mission of investigating the Earth's magnetosphere, the four Cluster satellites delivered high quality magnetic field data measured by the onboard fluxgate magnetometers (FGM). To achieve the accuracy required for scientific studies, the raw magnetic field data need to be calibrated on a regular basis. The calibration effort has been shared between the FGM team at the TU Braunschweig which performed the initial daily calibration necessary for the quick access to calibrated magnetic field data, and the FGM team at the Imperial College London (ICL) which performed the final calibration of the data. This work focusses on the in‐flight daily calibration, the final calibration results are discussed in this issue in a complementary paper prepared by the ICL team. We provide a brief overview of the methods employed for the daily calibration, present a statistical analysis of the daily calibration parameters and investigate their long‐term trends and their dependence on temperature.