On December 5, 2024, the Indian Space Research Organisation (ISRO) successfully launched the PSLV-C59 rocket from Sriharikota, Andhra Pradesh, carrying the European Space Agency's Proba-3 satellites. The two satellites onboard the PSLV rocket separated as planned, marking the mission’s success, ISRO confirmed.
"Mission Success! The PSLV-C59/PROBA-3 Mission has achieved its objectives, deploying ESA’s satellites into their designated orbit with precision," ISRO announced on X. "PSLV-C59 has soared into the skies, initiating a global mission led by NSIL, with ISRO's technical expertise, to deploy ESA’s innovative Proba-3 satellites," they added.
Originally scheduled for an earlier time, the launch was delayed to 4:04 pm on December 5 after an anomaly was detected in the propulsion system of one satellite the day before. The issue was resolved, and the revised countdown proceeded smoothly.
Proba-3, which stands for Project for Onboard Anatomy, features two spacecraft designed to fly in close formation, just one millimetre apart. Their mission is to study the Sun's outer atmosphere, known as the corona. The launch order was secured by NewSpace India Ltd, ISRO's commercial arm, from the European Space Agency.
This mission’s goal is to demonstrate precise formation flying, with two spacecraft, ‘Coronagraph’ and ‘Occulter,’ launched in a stacked configuration. This is not the first collaboration between ISRO and ESA, as ISRO had previously launched the Proba-1 mission in 2001.
Proba-3 Mission: Revolutionizing Satellite Formation Flying
The Proba-3 mission is a groundbreaking endeavor focused on demonstrating advanced satellite formation flying techniques with unparalleled precision. This mission involves two small satellites, launched together, that will separate and fly in tandem, aiming to lay the groundwork for future multi-satellite missions that will operate as a unified virtual structure.
Key Features and Goals
Proba-3 marks a significant leap in formation flying technology. The two satellites—the Coronagraph spacecraft (CSC) and the Occulter spacecraft (OSC)—will maintain their formation with extraordinary precision. They will remain aligned with just a few millimeters of separation and arc-second accuracy, even at a distance of around 150 meters, for up to six hours at a time.
The primary goal of Proba-3 is to facilitate the observation of the Sun’s corona, a phenomenon that requires creating conditions akin to a large-scale instrument. The Coronagraph spacecraft features a telescope, placed in the center of the shadow cast by the Occulter spacecraft, which will be positioned 150 meters away. The shadow is produced by an occulting disk on the OSC, a crucial part of maintaining the necessary conditions for studying the Sun's outer atmosphere.
Precision and Technology
Achieving the necessary precision to maintain the correct positioning of the Coronagraph within the shadow of the Occulter requires an advanced formation flying capability, down to a millimeter of accuracy. The system relies on highly efficient solar panels to power each satellite and ensure sustained operation during the mission.
The Occulter spacecraft is equipped with a 1.4-meter-diameter occulting disk that remains perpendicular to the Sun’s rays, creating a shadow of approximately 8 cm at a distance of 150 meters. The Coronagraph spacecraft, on the other hand, carries a scientific telescope with a 5 cm aperture. The mission aims to maintain the telescope’s aperture within this 8 cm shadow with millimeter precision, a feat achievable through precise formation flying.
Orbit and Duration
Proba-3 operates in a highly elliptical orbit, reaching altitudes over 60,000 km at its apogee, where the Earth’s gravitational pull is weaker, thus requiring less propellant to maintain the precise formation. The satellites will complete a 19-hour, 36-minute orbit, during which they can study the corona for six uninterrupted hours—a remarkable improvement in observation time, offering a factor of one hundred more continuous data collection compared to previous missions.
Previous Updates:
After Rescheduling, ISRO to Launch Proba-3 Mission Satellites Today
ISRO Reschedules PSLV-C59 Launch Due to Anomaly in PROBA-3 Spacecraft