The Martian crustal magnetic field as seen from MG and MAVEN

The magnetic figure of Mars was essentially constrained by the high quality measurements of Mars Global Surveyor (1996-2006). While the orbital parameters of this mission returned repetitive measurements on the night side (2:00 am) at a nearly constant altitude of 400km, the low altitude measurements were very sparse. The MAVEN mission (since 2014) is on an elliptical orbit around Mars, which provides a wealth of measurements at different local times and altitudes. With now almost three years of available measurements, it is possible to combine MAVEN and MGS observations and to compute a high resolution model of the martian magnetic field. This new model supersedes previously published models. It is based on Equivalent Source Dipoles (ESD), a discrete approach which benefits from the varying data distribution. It is converted into a spherical harmonics (SH) model which is stable up to degree 137, and can be used to predict the magnetic field at the surface of Mars with an unprecedented accuracy