“From here on, the spacecraft were maintaining their position autonomously, using the intersatellite link to exchange vital positioning information with each other,” notes Proba-3 systems engineer Teodor Bozhanov.

“Through the link, the Occulter spacecraft can also send instructions to its partner. If the positioning software detects a misalignment, the propulsion system can make small adjustments to get the two aligned again. At this stage, we were not interfering, only monitoring.

“For the Coronagraph spacecraft to move into the shadow cast by the Occulter, the system uses a set of shadow-detecting sensors that are located around the coronagraph instrument. This allows the satellites to stay in one line with the Sun.”