Parameters : Temperature profile Bulk iron and olivine weight fraction Pressure gradient. Modeling of the Martian mantle Recently taken into account : The effect of iron concentration in the respective minerals on the electrical conductivity The possible presence of partial melting in the upper mantle Empirical relation between olivine and the non-olivine mineralogical system.

Direct Problem See posters for details Direct Problem Inversion : Marginal density for temperature

Doppler simulation Analytical simulations of the Doppler and Range observables between Martian landers and an orbiter, extraction of the Martian orientation parameters + comparison with a direct lander-Earth link Effect of the network geometry and lander position on the parameters uncertainties (via analytical and numerical simulations) …

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Influence of the Free Core Nutation frequency on parameters estimation

Martian lithosphere and wavelets Aim: lithosphere thickness on Mars Method: 1.Input data : topography 2.Model : flexure of a thin elastic spherical shell 3.Output : predicted gravity anomalies 4.Localization of anomalies with spherical wavelets 5.Comparison of predicted/observed gravity anomalies Conclusion: large thickness at Tharsis, small at Hellas

Martian gravity anomalies from Mars Express data Collaboration with: 1.Jean-Pierre Barriot (CNES/Toulouse) for the software 2.Martin Paetzold (PI of MaRS) for the data Input data: line-of-sight Doppler residuals in areas of interest (poles…) Method: Least-squares inversion of residuals with a priori knowledge Result: local maps of gravity anomalies Work in progress: data is coming!

An improved strategy to estimate the zonal coefficients of the Martian gravity field : Numerical simulations of a global geodetic experiment Satellite ORBITS : - orbiter 1 (as part of a Mars Network Science Experiment : NEIGE) : i = 93.2°, e = orbiter 2 : i = 50°, e = Earth-based tracking of the two orbiters by 3 DSN stations Mars-based tracking of the near-polar orbiter (1) by 4 stations (dual frequency UHF/S-band)

Effect of inertial desaturation on the orbit determination When all the desaturation events are tracked from the Earth, only minutes of lander-orbiter tracking per week allows recovering of Mars’ orientation parameters with a precision of a few milli-arc-seconds When all desaturation events are tracked from the Earth: RMS of the residual positions of the orbiter : 4.8 cm Recovery of residual accelerations 6 events a day, 1 mm/s of velocity variation and 2 DSN antennas for tracking When half of the desaturation events are tracked from the Earth: RMS of the residual positions of the orbiter: 155 cm Recovery of residual accelerations 6 events a day, 1 mm/s of velocity variation and 1 DSN antenna for tracking

Variations of the low degree zonal (J2 to J5) coefficients of Mars’ gravity field Strong seasonal variation of gravity field due to sublimation/condensation of the atmospheric CO2 To constrain CO2 seasonal mass variations between polar caps and the atmosphere Prediction of changes of the first zonal terms of the gravity field provided by GCM (Global Circulation Model) simulations of the atmosphere Ls (Solar Longitude) From Laboratoire de Météorologie Dynamique (LMD), France From NASA

Estimation of Mars’ time dependent gravity field from MaRS Methodology of simulations Variable Gravity Field from GCM (Ames) predictions of J 2 to J 5 (or – C 20 to – C 50 ). Initial Values GINS (Géodesie par Integrations Numériques Simultanées) MGS-like orbits: 3 DSN (noise 0.1 mm/s) MEX-like orbit: 1 DSN (noise 0.05 mm/s) Model of forces acting on spacecrafts Determination of time dependent gravity field J2 to J5. Adjusted Values Evaluation of the adjustment from True error (Adjusted – Initial) Formal error (standard deviation from least squares process)

True error on adjustment MGS & MGS + MEX orbits The error is reduced by a factor of about 2 for even zonals and about 1.3 for odd zonals