ESA Proba-3 formation flying performance enabling low straylight sun corona observations

The ESA Proba-3 mission is a groundbreaking project to demonstrate and validate the concept of precise formation flying, with millimetric accuracy. It involves two spacecraft flying 150 meters apart and together forming a giant solar coronagraph. Following their launch in December 2024, the Proba-3 spacecraft entered routine science operations in July 2025. This paper presents the achieved formation flying performance of the Proba-3 spacecraft relevant for the coronagraphic observations, gathered from the satellites’ in-flight data. Moreover it describes how the formation flying enables the observation of the poorly explored inner region of the sun corona by minimizing the straylight level. Finally it discusses the main factors influencing the formation flying performance, including the on-board sensors accuracy, the satellites’ specific orbit and the capabilities of the propulsion system.