Determination of Earth’s Magnetic field from satellite constellation missions

Résumé:

While measuring the magnetic field gradient tensor in space is a major
technical challenge, the importance of magnetic gradiometry has been
recognized already several decades. In the near future the Swarm satellite
mission will for the first time measure the East-West gradient of the
magnetic field, which contains valuable information on the North-South
oriented features of crustal magnetization. In particular, the East-West
gradient measurements will resolve much smaller crustal structure than
possible by an analysis of the usual field components at the same
altitude.Going beyond Swarm, we performed a simulation of a full magnetic
gradiometry mission, emphasizing on the benefits of measuring the full
gradient tensor in addition to the three field components. Using simulated
orbits from a low Earth-orbiting satellite, synthetic data of the magnetic
field vector and of the nine elements of the magnetic gradient tensor are
calculated using a given (input) magnetic field model, for the various field
contributions (in the core, lithosphere, magnetosphere, and ionosphere).
From these synthetic data we estimate field models using either the magnetic
vector field measurements only or full gradient observations, and compare
our model retrieval with the original (input) model. The results show
evidently that the retrieval of the lithospheric field when using gradient
observations is significantly better than the retrieval using only vector
field data.

This study shows qualitatively the scientific benefit of measurements of the
gradient tensor in space.