Comparing Swarm's Nominal Level1b Magnetic Data and ASM Vector Field Experimental Data: a Convenient Tool for Understanding Data Quality Issues.

Friday, 19 December 2014
Laura Brocco1, Gauthier Hulot1, Pierre Vigneron1, Vincent Lesur2, Jean-Michel Leger3, Thomas Jager3, Francois Bertrand3, Olivier Sirol1, Xavier Lalanne1, Axel Boness3, Viviane Cattin3 and Isabelle Fratter4, (1)Institut de Physique du Globe de Paris, Paris, France, (2)Helmholtz Centre Potsdam GFZ German Research Centre for Geosciences, Potsdam, Germany, (3)CEA-LETI, Grenoble, France, (4)CNES French National Center for Space Studies, Toulouse Cedex 09, France
Swarm’s Absolute Magnetometers (ASM) provide scalar measurements of the geomagnetic field with high accuracy and stability on the three satellites of the mission. These measurements are used to produce the (nominal 1 Hz) Level1b scalar data and calibrate the (nominal 1 Hz) Level1b vector data provided by the Vector Field Magnetometer (VFM, located some distance away along the boom on which both instruments are installed). The very same ASM instruments, however, can also provide independent vector field measurements, which can next be used for comparison with the nominal Level1b vector data for quality crosschecks, possible detection of undesired satellite signals, and assessment of the stability of the mechanical link between both instruments on each satellite. Here, we report on the lessons learnt from such comparisons, focusing on the issues raised by systematic time-varying differences observed in the nominal L1b data between the modulus of the vector data and the scalar data, testifying for some local perturbations of the field measured.