Proba-3

ESA's Proba-3 mission uses two independent spacecraft as a distributed solar coronagraph and precision formation-flying demonstrator. Near the high point of their elliptical Earth orbit, the Occulter holds its disk roughly 150 metres ahead of the Coronagraph so the ASPIICS instrument can observe the faint inner corona. Cameras, laser metrology, and shadow sensors progressively refine the relative alignment, while autonomous control maintains the formation for hours. The formation is broken and reacquired on subsequent orbits, conserving propellant where Earth's gravitational gradient is weaker.