  Since the MICROSCOPE instrument aims to measure accelerations as low as a few
10$^{-15}$\,m\,s$^{-2}$ and cannot operate on ground, it was obvious to have a
large time dedicated to its characterization in flight. After its release and
first operation, the characterization experiments covered all the aspects of
the instrument design in order to consolidate the scientific measurements and
the subsequent conclusions drawn from them. Over the course of the mission we
validated the servo-control and even updated the PID control laws for each
inertial sensor. Thanks to several dedicated experiments and the analysis of
the instrument sensitivities, we have been able to identify a number of
instrument characteristics such as biases, gold wire and electrostatic
stiffnesses, non linearities, couplings and free motion ranges of the
test-masses, which may first impact the scientific objective and secondly the
analysis of the instrument good operation.
