METRIC: A Dedicated Earth-Orbiting Spacecraft for Fundamental Physics and Geophysics

A dedicated mission in low Earth orbit - called METRIC - is proposed to test selected predictions of gravitational theories and to measure directly the acceleration due to atmospheric drag in the altitude range considered, at the same time providing a metrological platform able to perform a tie between different space geodesy techniques. The core of the mission is a spacecraft of the micro class placed in an eccentric orbit between 450 and 1200 km of altitude. The satellite will be tracked from the ground with high precision and an on-board accelerometer package will measure the non-gravitational accelerations acting on it (e.g., atmospheric drag and solar radiation pressure). A precise orbit determination is expected to provide estimates of fundamental physics and geophysical parameters, while the accelerometer data are fundamental in constraining the atmospheric density variations. Along with the mission scientific objectives, a possible baseline for spacecraft configuration and a technique for the analysis of the non-gravitational perturbations is described in the paper.