Characterization of ISA — BepiColombo internal calibration source

BepiColombo, the forthcoming ESA (cornerstone) mission to Mercury, will include a comprehensive set of experiments - called Radio Science Experiments (RSE) in order to measure the gravitational field and rotational state of the planet and its rotation and to perform precise tests of Einstein's theory of general relativity versus other metric theories of gravity. Among the onboard instruments, a fundamental role in the RSE will be played by ISA (Italian Spring Accelerometer). This paper is devoted to the description of the main on-ground ISA internal actuators calibration and the obtained accuracy which is necessary to guarantee the accelerometer performance in order to reach the very ambitious objectives of RSE.