The Gamma Astrometric Measurement Experiment (GAME)

摘要

The GAME mission concept is aimed at the very precise measurement of the gravitational deflection of light by the Sun, by means of an optimised telescope operating in the visible and launched in orbit on a small class satellite. The targeted precision on the 7 parameter of the Parametrized Post-Newtonian formulation of General Relativity is 10~(-6) or better, i.e. one to two orders of magnitude better than the best currently available results. Such precision is suitable to detect possible deviations from the unity value, associated to generalized Einstein models for gravitation, with potentially huge impacts on the cosmological distribution of dark matter and dark energy. The measurement principle is based on the differential astrometric signature on the stellar positions, i.e., based on the spatial component of the effect rather than the temporal component as in the most recent experiments using radio link delay timing. Exploiting the possibilities offered by the observation strategy, it is also possible to target other interesting scientific goals both in the realm of General Relativity and in the observations of extrasolar systems. The instrument concept is based on a dual field, multiple aperture Fizeau interferometer, observing simultaneously two regions close to the Solar limb. The diluted optics approach is selected for achieving an efficient rejection of the diffracted and scattered solar radiation, while retaining an acceptable angular resolution on the science targets. The baseline design approach aims at minimization of the development criticality, whereas performance optimization may benefit from state of the art technologies e.g. active and lightweight optics. An internal metrology option is considered. We describe the science motivation, the proposed mission profile, the payload concept and the expected performance from recent results.