ESA GNC Conference Papers Repository

This paper presents the results of the CNES R&T study “GNC for the PEGASE mission” lead by Astrium and focusing on the system aspects of the Guidance, Navigation & Control (GNC) functional design for the PEGASE mission. The PEGASE mission aims at providing spectral characterization of hot Jupiters (Pegasides). The mission is based on a free-flying Bracewell type interferometer used in nulling mode and in imaging mode. Candidate architectures for interferometry missions such as PEGASE generally use accurate proportional thrusters. Relying on linear control techniques, these architectures allow a tight control of the formation geometry while internal control stages are still required at payload level to reach the accuracy needed to fulfil the scientific objectives. This paper proposes an alternative architecture based on mature actuators: wheels and pulsed cold gas thrusters. The limited performances of pulsed cold gas thrusters in term of Minimum Impulse Bit and impulsion repeatability requires relaxing the control threshold at formation level while keeping control performance at payload level unchanged. A key issue for this architecture is thus the performance allocation between the various control stages. Others challenges are the GNC design that mixed linear and dead band control techniques as well as the mastering of the wheel noise that is a major source of perturbations. The paper details the GNC sizing and design and presents the promising simulation results.