Abstract
The ESA mission BepiColombo will explore the planet Mercury with equipment allowing an extremely accurate tracking. While determining its orbit around Mercury, it will be possible to indirectly observe the motion of its center of mass, with an accuracy several orders of magnitude better than what is possible by radar ranging to the planet’s surface. This is an opportunity to conduct a relativity experiment which will be a modern version of the traditional tests of general relativity, based upon Mercury’s perihelion advance and the relativistic light propagation near the Sun. We define the mathematical methods to be used to extract from the data of the BepiColombo mission, as presently designed, the best constraints on the main post-Newtonian parameters, especially and the Nordtvedt parameter but also the dynamic oblateness of the Sun and the preferred frame parameters We have performed a full cycle simulation of the BepiColombo radio science experiments, including this relativity experiment, with the purpose of assessing in a realistic (as opposed to formal) way the accuracy achievable on each parameter of interest. For the best constraint can be obtained by means of a dedicated superior conjunction experiment, with a realistic accuracy For the main problem is the very strong correlation with if the Nordtvedt relationship is used, as it is legitimate in the metric theories of gravitation, a realistic accuracy of for and for can be achieved, while itself is constrained within If the preferred frame parameters are included in the analysis, they can be constrained within and respectively, at the price of some degradation in and It is also possible to test the change with time of the gravitational constant G, but the results are severely limited because of the problems of absolute calibration of the ranging transponder, to the point that the improvement as compared with other techniques (such as lunar laser ranging) is not so important.
- Received 27 September 2001
DOI:https://doi.org/10.1103/PhysRevD.66.082001
©2002 American Physical Society