In-flight validation of the formation flying technologies using the ASPIICS/PROBA-3 giant coronagraph

Classical externally-occulted coronagraphs are presently limited in their performances by the distance between the external occulter and the front objective. Formation flyers open new perspectives and allow conceiving giant, externally-occulted coronagraphs using two-spacecraft system. The PROBA-3 formation flying demonstration mission, currently in its preparatory study phase, is intended to incorporate the ASPIICS (Association de Satellites Pour l'Imagerie et l'Interfromtrie de la Couronne Solaire) scientific payload. ASPIICS is a solar coronagraph designed to observe from the coronal base out to 3 solar radii with high spatial resolution in the visible range. Formation flying technique imposes new constraints and major challenges in particular in terms of metrology. ASPIICS will both use and demonstrate the formation flying features and performances. In order to fully validate the formation flying technique and to improve the scientific return, original developments linked to the formation flying constraints have been made these last years and are presented in this article.