Gravitation and Geodesy with Inertial Sensors, from Ground to Space
P. Touboul (ONERA)
G. Métris (Geoazur – CNRS/UMR)
H. Sélig (ZARM Space Science Department University of Bremen)
O. Le Traon, A. Bresson, N. Zahzam, B. Christophe, M. Rodrigues (ONERA)
Since the years 2000, three space missions, CHAMP, GRACE, and GOCE, have led us to consider the Earth's gravitational field and its measurement in a new light, using dedicated sensors and adequate data processing, revealing the changes in the Earth's field as the true signal rather than the disturbing terms in addition to the geostatic reference field. Besides the possibilities offered by new technologies for the development of inertial sensors, a space environment of course involves special constraints, but also allows the possibility of a specific optimization of the concepts and techniques well suited for microgravity conditions. We will analyze and compare with others the interest in the electrostatic configuration of the instruments used in the main payload of these missions, and we will consider the recent MICROSCOPE mission, which takes advantage of the same mission configuration as a gradiometry mission to test the universality of free fall whatever the mass composition. A few days after launching the satellite in April 2016, we will show how we intend to validate the future result, the existence or not of a violation signal of the equivalence principle, taking into account the laboratory tests, where available, and the in-flight demonstrated performance during the calibration phases and the scientific measurements. With regard to ground measurements, either fixed or mobile, or under marine or aircraft conditions, we will demonstrate the complementary interest of the atomic interferometer. Finally, we will briefly discuss the future envisaged for these technologies, like that already implemented in the Lisa-Pathfinder mission without a gold wire for the electrical control of the charges of the mass, and these types of mission.