This week, the Proba-3 spacecraft took a giant leap toward achieving the mission’s ultimate goal. The satellites autonomously acquired and maintained formation, with the CSC pointing toward the Sun while staying aligned in the OSC shadow — a crucial step for the groundbreaking coronagraphy ahead.

On Monday, the Proba-3 team gathered once more in the control room at ESEC Redu, with one objective in mind: achieving and maintaining autonomous formation flying. System engineers, satellite operators and subsystem experts joined forces, ready to push the boundaries of technology demonstration.

The process began with bringing the spacecraft in the “formation flying envelope” through a series of precisely calculated maneuvers. Then, once close to the apogee of their orbit around the Earth, the operators commanded the desired orientation, allowing the satellites to start pointing at each other.

Then came the big moment: from this point forward, everything happened autonomously. The Narrow Angle Camera (NAC) on the Occulter spacecraft (OSC) successfully detected the Coronagraph spacecraft (CSC), the on-board navigation converged, and the formation flying started in a completely autonomous way! The CSC had to slowly move about 50 meters to reach its target location on the other side of the OSC shadow, and then maintained its aligned position.

With this milestone reached, it was the perfect opportunity for another exciting test: activating the Shadow Positioning Sensor (SPS) onboard the CSC. This unit detects the shadow cone cast by the OSC. Using these readings, the team fine-tuned small position offsets, ensuring the Occulter’s shadow was well centered on the Coronagraph — a key requirement for future solar observations. A future step will be to allow the spacecraft to control the formation including the SPS information, in closed-loop.

Below, you can see an impressive sequence of images taken by the NAC, capturing the CSC entering alignment with the OSC.

After a few hours of autonomous formation flying, the pair performed a maneuver to break their formation and safely continue their way toward perigee. But the challenge wasn’t over yet. Upon approaching apogee again, the spacecraft had to reacquire their formation, and they did it flawlessly. Of course, as this was being done for the first time, it was still performed under close supervision by the ground control, but the results are very promising for future formations.

The data gathered over these two orbits will now be analyzed to calibrate the formation flying system to improve the accuracy, bringing Proba-3 one step closer to its ultimate mission: observing the solar corona with unparalleled precision.

Stay tuned for more exciting updates from Proba-3!