The BepiColombo ISA accelerometer: Ready for launch

The Italian Spring Accelerometer (ISA) is an high-sensitivity instrument designed to measure very small accelerations. As such, it is suitable for a number of applications, notably the measurement of non-gravitational accelerations acting on the surface of a spacecraft. ISA has been selected to fly on board the forthcoming BepiColombo mission for the exploration of the planet Mercury; it is part of the suite of instruments which will perform the so-called Radio Science Experiments (RSE) to study gravitational field, internal structure and rotational state of Mercury, as well as to verify some predictions of the general theory of relativity. In this work the concept and design of ISA are described, along with important calibration and performance evaluation activities.