An Algorithm For Deriving Core Magnetic Field Models From Swarm Data Set
Rother, Martin; Lesur, Vincent; Schachtschneider, Reyko
Helmholtz-Zentrum Potsdam - Deutsches GeoForschungsZentrum GFZ, GERMANY

In view of an optimal exploitation of the Swarm three satellite data set, we have prepared and tested a software dedicated to the determination of (1) accurate core magnetic field models, and (2) Euler angles between the magnetic sensors and the satellite reference frame. The dedicated core field model software is closely related to the GFZ Reference Internal Magnetic Model (GRIMM) inversion and modelling family, which was developed mainly for handling the German CHAMP satellite data. The data selection technique and the model parameterization are similar of what was used for the derivation of the third GRIMM model, although the usage of observatory data is not planned. Due to the orbit definition of the Swarm mission, the gaps induced by the local-time selection scheme applied to the data will vanish in the course of the mission. The regularization technique applied during the inversion process smoothes the magnetic field model in time. The algorithm to estimate the Euler angles between the satellite reference frame and the magnetic sensors is also derived from the CHAMP studies. The inversion scheme includes Euler angle determination with a quaternion representation for describing the rotations and their determination. It has been built to handle possible weak time variations of these angles. The modelling approach and software has been initially validated on a simple, noise free, synthetic data set and on CHAMP vector magnetic field measurements. We will present results of test runs applied at least on the synthetic Swarm test data set (TDS-1), which is made of vector magnetic data in sensor system.