In-orbit performance of the Coupled Dark State Magnetometer aboard the China Seismo-Electromagnetic Satellite

The High Precision Magnetometer package aboard the China Seismo-Electromagnetic Satellite (CSES) consists of two FluxGate Magnetometers (FGM) and a Coupled Dark State Magnetometer (CDSM). The CDSM is an optical scalar magnetometer which measures the magnitude of the magnetic field with low absolute error. It serves as baseline for the linear calibration of the FGMs which detect the direction of the magnetic field but with limited accuracy due to inherent uncertainties such as sensor gain, offset and orthogonality.

The CDSM is based on two-photon spectroscopy of free alkali atoms and uses several Coherent Population Trapping resonances in parallel to reduce systematic errors caused e.g. by the sensor temperature dependence, the limited stability of the microwave oscillator or varying light intensity. The CSES mission is the first demonstration of the CDSM measurement principle in space [1].

The presentation summaries the key performance characteristics derived from the ground calibration and introduces the correction steps which are required to clean the in-orbit data. The data quality is demonstrated with a comparison to the SWARM satellite magnetometers via the CHAOS model.

[1] A. Pollinger, R. Lammegger, W. Magnes, C. Hagen, M. Ellmeier, I. Jernej, M. Leichtfried, C. Kürbisch, R. Maierhofer, R. Wallner, G. Fremuth, C. Amtmann, A. Betzler, M. Delva, G. Prattes and W. Baumjohann, Coupled Dark State Magnetometer for the China Seismo-Electromagnetic Satellite, Meas. Sci. Technol. 29, 095103 (2018).