MG11 
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Metric extensions of General Relativity and gravity tests in the solar system

Validity of general relativity has been confirmed at distance scales ranging from the millimeter to the size of planetary orbits. The anomalous acceleration recorded on Pioneer 10/11 probes on their escape trajectories outwards the solar system might constitute a first hint that gravity laws should be modified at large scales. This observation can be made compatible with other gravity tests in the solar system provided the metric interpretation of gravity is extended beyond General Relativity and beyond PPN frames. These metric theories can in fact be seen as extensions of PPN where the parameters $\beta$ and $\gamma$ may depend on the heliocentric distance. They could have observable signatures to be looked for by existing or new gravity tests in the solar system.

Gravity tests and the Pioneer anomaly

Validity of general relativity has been confirmed at distance scales ranging from the millimeter to the size of planetary orbits. But windows remain open for potential violations at shorter or longer scales. The anomalous acceleration recorded on Pioneer 10/11 probes on their escape trajectories outwards the solar system might constitute a first hint that gravity laws should be modified at large scales. Observation of this "Pioneer anomaly" will be presented and the question of its compatibility with other gravity tests in the solar system then discussed.