ISRO To Launch 2 European Satellites That Will Mimic Total Solar Eclipse

On its 61st flight, India's workhorse rocket has been tasked by the European Space Agency (ESA) to launch a very special pair of satellites that will simulate the total solar eclipse through precision formation flying in space.

The satellites, Proba-3, will lift off from Andhra Pradesh's Sriharikota using the Polar Satellite Launch Vehicle (PSLV) on Wednesday at 4.08 pm.

The Indian Space Research Organisation (ISRO) said the PSLV-C59 vehicle will carry the Proba-3 spacecraft into a highly elliptical orbit as a dedicated commercial mission of New Space India Limited (NSIL), ISRO's commercial arm.

The Proba-3 satellite is an in-orbit demonstration (IOD) mission of the ESA. The mission goal is to demonstrate precise formation flying. It consists of two spacecraft, namely the Coronagraph Spacecraft (CSC) and the Occulter Spacecraft (OSC). They will be launched together in a stacked configuration.

The two satellites together weighing 545 kg will be hoisted into space using the 44.5-metre-tall Indian rocket that weighs 320 tonnes at lift-off. About 18 minutes after lift-off, the two satellites will be released at an altitude of 600 km above the Earth.

"This launch requires a highly precise injection of the European satellites," ISRO Chairman Dr S Somanath told NDTV.

"When operational, the two satellites will work in unison and behave like the Earth and Moon to mimic a six-hour daily space-based total solar eclipse," said professor Dipankar Banerjee, a solar physicist and Director of ISRO's Indian Institute of Space Technology in Kerala's Thiruvananthapuram.

One spacecraft flying closer to the Sun will cast a precise shadow on the second satellite flying 150 metres away from it. This will create an artificial solar eclipse in space. Each orbit will give scientists a six-hour window to mimic a space-based artificial solar eclipse. The ESA has spent nearly 200 million euro in making this mission with Belgium and Spain being the lead countries.

The ESA in a statement said through exquisite, millimetre-scale, formation flying, the dual satellites making up ESA's Proba-3 will accomplish what was previously a space mission impossible - cast a precisely held shadow from one platform to the other, in the process blocking out the fiery face of the Sun to observe its ghostly surrounding atmosphere on a prolonged basis.

The corona of the Sun has remained a mystery and whenever a natural total solar eclipse happens, scientists get only a few minutes to study this ultra-hot part of the Sun. The study may also help understand solar storms.

The ESA said the Proba-3 is the third small satellite technology development mission to demonstrate the technologies required for formation flying of multiple spacecraft in the fields of space science, Earth observation and surveillance. This involves the in-orbit validation of these new formation flying techniques and technologies through a series of precision. It is like two acrobats performing in precise unison in the vacuum of space and in an autonomous manner.

The Proba-3 mission concept comprises two independent mini-satellites flying in formation, close to one another with the ability to accurately control the attitude and separation of the two satellites, all in an effort to simulate a total solar eclipse.

The ISRO said Proba-3 is ESA's and the world's first precision formation-flying mission. A pair of satellites will fly together, maintaining a fixed configuration as if they were a single large rigid structure in space, to prove innovative formation flying and rendezvous technologies.

"This needs millimetre level accuracy between the satellites even as they race around the Earth," Dr Somanath said.

India's first space-based solar observatory, the Aditya L1, launched in 2023 and which cost Rs 400 crore has the capability to mimic a solar eclipse on a continuous basis using the Visible Emission Line Coronagraph (VELC).

This is the second ESA satellite to be launched on an Indian rocket. In 2001, the Proba-1 mission was also launched by the PSLV, a mission that was to last one year but lasted more than two decades.

Some say the precise launch by India enormously helped ESA get this long life.

"This is a commercial launch and not a collaborative effort," said Radhakrishnan Durairaj, Chairman and Managing Director of New Space India Limited.

"So far the PSLV has had 11 fully commercial missions and Proba-3 is the 12th fully commercial mission," Mr Durairaj said.