Isro reschedules Proba-3 mission launch to December 5. Here's why

The Indian Space Research Organisation (Isro) announced that the launch of the European Space Agency’s (ESA) Proba-3 mission, initially scheduled for December 4, has been postponed. The new launch time is set for 4.12 pm on Thursday, December 5, aboard the Polar Satellite Launch Vehicle (PSLV-XL).

 

This delay follows the identification of an anomaly, as mentioned by Isro.

 

In the post on X (formerly Twitter), Isro said, “Due to an anomaly detected in Proba-3 spacecraft PSLV-C59/PROBA-3 launch rescheduled to tomorrow at 16.12 hours.” 

The Proba-3 mission is significant as it marks a historic collaboration between ESA and Isro. It is the first satellite launch between the two agencies since the Proba-1 Earth observation mission in 2001, highlighting ISRO’s growing role in global space exploration with its efficient and reliable PSLV platform.

What is the Proba-3 mission?

The PSLV, India’s first launch vehicle with liquid stages, is designed to carry satellites and other payloads into space as required by Isro. The PSLV’s debut launch took place successfully in October 1994. For the Proba-3 mission, the European team in India has completed the integration of the spacecraft, which was enclosed within the payload fairing, followed by a dress rehearsal for the launch.

 

Proba-3 is a joint mission to study the Sun’s corona, the outermost layer of its atmosphere, which is vital for understanding solar activity and space weather.

Formation flying and solar eclipses

Isro said that Proba-3 will consist of two spacecraft: the Occulter Spacecraft (OSC) and the Coronagraph Spacecraft (CSC). These will launch together in a "stacked configuration" and work collaboratively to simulate artificial solar eclipses. This mission is the first-ever precision formation flying operation, where the two satellites will maintain a 150-metre distance in highly elliptical orbits.

 

This setup allows for extended observations of the solar corona — up to six hours — compared to the brief duration of natural eclipses. The Occulter will block sunlight, allowing the Coronagraph to study solar phenomena that are difficult to observe.

PSLV-XL: Enhancing mission capabilities

The PSLV-XL variant, which features additional strap-on boosters, is known for its increased payload capacity. It will launch the combined 550 kg of the Occulter and Coronagraph spacecraft. Isro confirmed that the mission will unfold in four stages, with the launch vehicle carrying a total mass of around 320 tonnes.

 

Isro further said this mission highlights the PSLV’s ‘trusted precision’ and underscores the importance of international collaboration in space exploration.