GAME/ISAS development status

The Gravitation Astrometric Measurement Experiment (GAME) is a space mission for Fundamental Physics tests in the Solar system, through coronagraphy and Fizeau interferometry for differential astrometry. The precision goal on the γ and β General Relativity PPN parameters is respectively in the 10-8 and 10-6 range. The design is focused on systematic error control through multiple field simultaneous observation and calibration. The GAME instrument concept is based on multiple aperture Fizeau interferometry, observing simultaneously regions close to the Solar limb (requiring the adoption of coronagraphic techniques), and others away from the Sun. The diluted optics approach is selected to achieve an efficient rejection of the scattered solar radiation, while retaining an acceptable angular resolution on the science targets. The Interferometric Stratospheric Astrometry for Solar system (ISAS) project is a GAME technology demonstrator, providing milli-arcsec level astrometry on the main planets of the Solar System. The ISAS technical goal is the validation of basic concepts for GAME, in particular integration of Fizeau interferometry and coronagraphic techniques by means of pierced silicon carbide (SiC) mirrors, intermediate angle dual field astrometry, smart focal plane management for increased dynamic range and pointing correction. The ISAS instrument concept is a dual field, multiple aperture Fizeau interferometer, using coronagraphy for observation of Solar System planets also close to the Sun. A prototype SiC multi-aperture mirror was manufactured by Boostec (F), and has been investigated by thermo-elastic analysis to define the applicability to both GAME and ISAS designs. We describe the development status of both stratospheric and space options, as well as the current extrapolation of the SiC prototype characteristics to the GAME and ISAS optical configurations.