Simulation of the metrology of the PROBA-3/ASPIICS formation flying solar coronagraph

International audienceFormation Flying is now considered to be the most promising and effective approach to deploy the forthcoming generation of very large instruments in space. PROBA-3 is a technology mission devoted to the in-orbit demonstration of formation flying techniques and technologies. PROBA-3 will implement a giant coronagraph (called ASPIICS) that will both demonstrate and exploit the capabilities and performances of formation flying. ASPIICS is distributed on two spacecrafts separated by 150m, one hosting the external occulting disk and the other the optical part of the coronagraph. ASPIICS will incorporate metrology units which will allow determining both the absolute pointing and the relative alignment of the formation. Photosensors located around the entrance pupil of the coronagraph will determine the absolute positioning of the instrument by sensing the penumbra behind the occulting disk. Light sources located on the rear-side of the occulting disk will allow verifying the alignment of the formation. We carried out a complete numerical simulation of the metrology system and showed how corrections are derived from the measurements to be applied to each spacecraft in case of misalignments. This simulation was validated by a scaled model of the coronagraph developed at Laboratoire d'Astrophysique de Marseille. This study has been conducted in the framework of an ESA "STARTIGER" Initiative, a novel approach aimed at demonstrating the feasibility of a new and promising technology on a very short time scale (six months)