Speaker
Description
Active Debris Removal (ADR) is the ultimate technical solution to enforce a zero debris policy in the presence of old space objects which were not designed to be deorbited, or in case of malfunction of a deorbiting system. Such a technology is, however, extremely complex due to the noncooperative nature of the target and therefore often very expensive. ClearSpace intends to demonstrate the technical feasibility and commercial viability of ADR service by the means of two missions: ClearSpace-1, funded in the frame of ESA’s ADRIOS program, and CLEAR, funded by the UK Space Agency.
The presentation provides an overview of the overall GNC concept, able to fulfil challenging technical requirements while already seeking for low recurring costs. To that end, the close-range navigation relies only on passive imagery in the visible spectrum, making it reliant on favorable illumination conditions. It is furthermore foreseen to capture the target while the relative motion is synchronized. This results in a complex guidance function, which plans and executes in real real-time a synchronization trajectory satisfying numerous constraints, such as available control authority or illuminations conditions. Finally, a precise, reactive and robust controller is needed to follow accurately this very dynamical trajectory in the presence of severe disturbances due to flexible appendages and ensure successful control of the stack after capture while the knowledge of the center of mass and inertia properties is still uncertain.
Special attention is also paid to the minimization of risk of collision during the rendezvous and capture phase. At large distance, the mission relies on passive safety, which allows for a dramatic reduction of the propellant budget in case of anomaly and for a significant gain of time while recovering the mission. However, this can only be applied to the early phases of the rendezvous. Therefore, active collision avoidance manoeuvring (CAM) capability is also needed, which inevitably leads to the complex design of escape manoeuvres, since the mission aims at capturing a noncooperative target following a specific direction in the target body frame. This finally raises the need for efficient real-time onboard detection of anomalies to trigger properly the CAM. The main safety strategies retained to ensure mission safety are depicted in the last part of the presentation.
