The Proba-3 Program Takes an Important Step Forward

The Proba-3 program has reached multiple relevant milestones in the integration of the two satellites that will, for the first time, demonstrate a high-precision formation flight in space.

In the future, spacecraft formation flying technology will be used to replace bulky structures (such as telescopes) with small independent platforms, which are easier to launch into space and can be combined to form large assemblies that work as a single entity, while achieving equivalent performance.

In parallel, Proba-3 will perform scientific observations taking images of the Sun's corona by means of a coronagraph instrument, placed in one of the spacecraft. Formation flying technology entails placing one of the two satellites in front of the instrument's lens, thus blocking out the sun's disk and creating an artificial eclipse in flight.

For SENER Aeroespacial, the project's prime contractor for ESA, Proba-3 marks a technical milestone, since it is the first time that a Spanish company has led the full development (i.e., is responsible for the entire flight and ground system) of a European Space Agency mission.

The project has made an important step ahead with the start of the integration of the flight equipment, after the delivery of the platforms of the two satellites by Airbus Defence and Space. In this program, Airbus manufactures and integrates the platforms of both satellites. The first one, called Coronagraph Spacecraft (CSC), contains the main instrument (coronagraph), whereas the second satellite, called Occulter Spacecraft (CSO), carries an occulting disk that will cover the sun's disk as seen from the other satellite. Airbus delivered the structure of both satellites already integrated with the propulsion system, harness and the thermal control system. This platform integration was carried out at the company's facilities in Madrid (Spain).

The two satellites are now at the QinetiQ facility in Kruibeke (Belgium). For this program, QinetiQ is leading the activities to develop the avionics system, integrate all the electronic units within the platform, perform overall system verification and prepare the operations. The first flight equipment is already being installed on the OSC, and the integration of the CSC is expected to start early 2022, as this last unit was received in mid-December.

At the same time, SENER Aeroespacial has completed the activities related to the design, manufacturing and testing of the high-stability Optical Bench Assembly (OBA) of the Coronagraph spacecraft. The bench has been assembled in SENER Aeroespacial facility in Bilbao (Spain). The last step has been the integration of the coronagraph instrument, the cornerstone of Proba-3 scientific mission, developed by a consortium led by CSL. Such integration of the payload in the OBA has been realized by a joint team of CSL and SENER Aeroespacial employees, making use of the CSL facilities in Liege (Belgium). The bench and instrument are now at QinetiQ, ready to be integrated into the CSC.

Once the integration work is complete, an intensive testing campaign will begin prior to the launch planned for 2023.

Proba-3 is the world's first high-precision formation flying mission in space. The two satellites will stay 150 m (≈500 feet) apart, forming a large rigid virtual structure, with a relative accuracy between them on the order of millimeters and arcseconds. They will be used to validate the technology needed for precision formation flying.

Formation flying will be a key technique for future space science missions. Among other things, it will be used to develop large telescopes whose main elements (such as lenses and detectors) need to be located far away from one another while at the same time holding their relative positions and distances with a high degree of accuracy and stability. This technology will bypass the need to resort to heavy and bulky deployable structures, which may not fit in current launchers or, at best, would make them extremely expensive to put into orbit and operate.

The manufacturing, integration and verification phase is already underway and is progressing at a good pace, the goal being to launch Proba-3 in 2023. Following the usual launch and early orbit phase (LEOP), an orbital verification phase will take place that will last for several months before the system is handed over to ESA, which will operate it for the remainder of the mission life, which is expected to last a total of two and a half years.

(Image provided with QinetiQ news release)