ISRO's ESA Proba-3 launch postponed: Here's what we know so far

ESA Director General Josef Aschbacher reported that an anomaly occurred in the redundant propulsion system of the Coronagraph spacecraft, which was part of the PSLV-C59 mission. Scientists are currently working to identify the cause of the issue.

"During Proba3's pre-launch preparations at the Satish Dhawan Space Centre in India, an anomaly in the redundant propulsion system of the Coronagraph Spacecraft occurred. This propulsion system is part of the attitude and orbit control subsystem of the satellite and used to maintain orientation and pointing in space." Aschbacher said in a social media post.

He added, "The anomaly is being thoroughly investigated. The mission control team at ESA’s ESEC centre in Redu, Belgium, is assessing the use of a software solution to enable the launch scheduled for Thursday, 5 December, at 11:34 CET (10:34 GMT, 16:04 local time)."

PROBA-3 is world’s first precision formation-flying mission, where two satellites, the Coronagraph Spacecraft (CSC) and the Occulter Spacecraft (OSC), will fly 150 meters apart, maintaining a fixed configuration like a single large rigid structure in space, to prove innovative formation flying and rendezvous technologies.

The Occulter Spacecraft (OSC), has a 1.4-meter occulting disk that will cast a shadow, about 8 cm wide, on the second satellite, the Coronagraph Spacecraft (CSC). The CSC, equipped with a 5 cm telescope, must stay within this shadow with millimeter precision.

The satellites will maintain this precise formation flying at apogee, about 60,000 km, where less propellant is needed. This will allow continuous corona observation for six hours during each 19-hour, 36-minute orbit, significantly improving study time.

The mission seeks to capture unparalleled details of the Sun’s faint corona, offering insights into solar dynamics, the corona's high temperature, and the acceleration of solar wind. It also aims to deepen our understanding of solar storms and coronal mass ejections, which impact Earth's communication systems, satellites, and power grids.

Proba-3 will serve as a space-based laboratory to test strategies, guidance, navigation, and control systems, along with algorithms like relative GPS navigation that were previously tested in ground simulators. These techniques and simulators developed for Proba-3 will be made available for broader use, playing a key role in preparing for future missions, according to ESA.

The launch will also highlight ISRO's growing space technology capabilities, with the PSLV-XL rocket being used for the 61st flight of the PSLV and the 26th use of its PSLV-XL configuration.

The mission aims to capture continuous, detailed images of the Sun’s corona to improve our understanding of solar activity and space weather, while also demonstrating advanced precision formation flying, with the satellites maintaining a precise 150-meter separation as a unified system.

*With Agency Inputs