Design of Super-Twisting Sliding Mode Observer for LISA Mission Micro-Meteoroid Impact

LISA (Laser Interferometer Space Antenna) is a space mission, under study by the European Space Agency (ESA) and other institutions, with the objective of detecting, observing, and measuring gravitational waves. It consists of a triangle constellation of three spacecraft connected through bidirectional laser links to measure gravitational waves by means of interferometry. During the Science mode, also called Dragfree mode, micrometeoroids may collide with the spacecraft surface, generating impulsive forces and torques, which can cause the loss of links. Impulsive disturbances may lead to a significant performance degradation and even to instability, especially in the presence of actuator saturations. In this paper, a Navigation algorithm based on a sliding mode observer is proposed to improve the closed-loop system stability properties, allowing the spacecraft to quickly restore the laser links, safely returning to the Science mode. Simulation results show the effectiveness of the proposed solution. Moreover, a comparison with classical methods is carried out, based on the combination of an Extended Kalman Filter and an Anti-windup strategy.