Proba-3 Mission Carries Out Its First Autonomous Formation Flying Operations in Orbit

The European Space Agency’s (ESA) Proba-3 mission, led by Sener in close collaboration with an industrial team comprising Redwire, Airbus, GMV, and Spacebel, and involving a broad consortium of over 29 companies from 17 countries, was launched on 5 December 2024 and is currently in its commissioning phase in orbit.

The mission aims to demonstrate the feasibility of high-precision formation flying between spacecraft, using cutting-edge new technology. It involves the synchronisation of two satellites flying in an elliptical orbit, reaching distances of over 60,000 km from Earth (more than ten times the distance from the Earth’s surface to its core). In this same mission, formation flying technology is also used to capture images of the solar corona (coronagraphy). The Coronagraph satellite houses the mission’s coronagraph, an instrument that points directly at the Sun. The second satellite, the Occulter, eclipses the Sun by positioning itself between the star and the Coronagraph. Using a range of metrology equipment (optical and laser), the two satellites are maintained at a distance of approximately 150 metres, with extremely high precision (within a few millimetres).

In recent weeks, the team operating the satellites from the ESEC control centre in Redu, Belgium – comprising ESA, Sener, and Redwire personnel with support from GMV experts – has achieved a key milestone: entry into the mission’s first operational orbits, where formation flying operations are conducted. In these orbits, the satellites manoeuvre into the optimal relative position for coronagraphy at apogee, using various sensors in sequence: first the WAC and NAC cameras of the Visual-Based System, then the Fine Lateral and Longitudinal Sensor (a laser system), and finally the Shadow Position Sensor, integrated within the coronagraph itself. The formation is maintained continuously for a six-hour period before being broken with new manoeuvres as the satellites pass through perigee. All these operations are carried out entirely autonomously, without operator intervention, although still under the monitoring of the operations team in Redu.

These latest activities have confirmed not only that the Formation Flying System’s logic is functioning correctly, but also that the system achieves its millimetric performance targets. The operations team is now preparing for the final activities of the commissioning phase, particularly the use of this novel formation flying technology to capture images of the solar corona.

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