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)

…

jours 7000700 700 700 7000 0 0

Influence of the Free Core Nutation frequency on parameters estimation

Martian lithosphere and wavelets

• Aim: lithosphere thickness on Mars• Method:1. Input data : topography2. Model : flexure of a thin elastic spherical shell3. Output : predicted gravity anomalies4. Localization of anomalies with spherical wavelets5. 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 software2. 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 = 0.001

- orbiter 2 : i = 50°, e = 0.0206• 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 15-20 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 accelerations6 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 accelerations6 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 J2 to J5 (or – C20 to – C50). 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