The mission aims to demonstrate high-precision formation flying for space observation, including studying the sun’s corona

India’s space agency, ISRO, has successfully launched two satellites in collaboration with the European Space Agency (ESA), marking a significant milestone in the study of the Sun’s outermost layer, the corona. The satellites, part of the Proba-3 mission, are set to demonstrate unprecedented precision in formation flight, a technique that could revolutionise future space observatories.

The launch took place aboard ISRO’s PSLV-XL rocket and went off without a hitch, with the mission showcasing a flawless separation of the spacecraft via the Passive Spring-Out Mechanism, followed by satellite ignition and separation. The two ESA satellites, Coronagraph and Occulter, will now begin their journey to maintain an incredibly tight formation. This precision flying is critical to the success of the mission, as the Occulter will position itself precisely between the Coronagraph and the Sun, effectively blocking out the Sun’s light. This will allow Coronagraph to study the solar corona, a phenomenon visible from Earth only during rare solar eclipses.

The precision required for this mission is extraordinary—angles between the two spacecraft must differ by minuscule distances, measured in arc seconds. The success of this formation flight could pave the way for future missions where multiple satellites work together as a virtual observatory.

The satellites are expected to fly in close formation for six-hour stretches before drifting apart to conserve fuel. During these operations, they will demonstrate key space techniques, including rendezvous, separation, proximity operations, and convoy flying. Each orbit will allow the team to test and refine these processes, essential for missions like Mars Sample Return or satellite servicing.

Beyond its primary goal of observing the Sun, the Proba-3 mission also serves as a test bed for other potential applications of formation flying. ESA envisions that successful formation flights could enhance satellite servicing, Earth observation, and scientific exploration. Furthermore, the mission will test techniques for collision avoidance, a crucial factor in the increasingly crowded space environment.

Proba-3’s mission success could lead to more ambitious ESA projects, including the Laser Interferometer Space Antenna (LISA) slated for a 2035 launch. LISA will involve three spacecraft flying in a triangular formation to detect gravitational waves—a major leap forward in the study of black holes and cosmic phenomena.

The Proba-3 mission also highlights the growing collaboration between ESA and ISRO. With recent delays in the Ariane 6 and Vega-C rockets, ISRO’s PSLV rocket has emerged as a reliable and cost-effective option for ESA, particularly for smaller payloads like Proba-3.

If the mission succeeds, it could set the stage for a new era of collaborative space exploration, with multiple spacecraft operating in precise formation for scientific discovery.