ISRO’s PSLV places two satellites of European Space Agency into orbit

Sriharikota: In a first-of-its-kind initiative involving precision-flying, ISRO on Thursday successfully launched the Proba-3 mission onboard a PSLV-C59 rocket, a solar experiment undertaken by the European Space Agency.

ISRO placed the two satellites into the ‘right orbit’ around 18 minutes after lift-off, said Chairman S Somanath.

The Proba-3 (Project for Onboard Autonomy) mission consists of a twin satellite in which two spacecraft (placed inside the satellites) would fly together as one, maintaining a precise formation down to a single millimetre to study the Sun’s outer atmosphere.

NewSpace India Ltd, the commercial arm of ISRO has bagged the order from ESA for the launch, which was a technology demonstration mission.

The mission objective is to demonstrate precise formation flying and the two spacecraft inside the satellites–Coronagraph (310 kg) and Occulter (240 kg) would be launched together in a stacked configuration after the desired orbit level is reached.

At the end of the revised countdown, the 44.5 metre tall PSLV-C59 rocket on its 61st flight and the 26th with PSLV-XL variant lifted off at the prefixed 4.04 pm from this spaceport here.

After soaring into the skies on an 18-minute journey, the rocket successfully separated the two satellites into intended orbit which would be later positioned at the desired orbit by the scientists of ESA in Belgium.

The satellites, as planned, reached the High Earth Orbit and would have a 19.7 orbital period with 60,530 km of apogee (farthest point from the Earth) and 600 km perigee (closest point to the Earth).

Later, the satellites would fly 150 metres apart (as one large satellite structure) in tandem so that the ‘Occulter’ spacecraft would block out the solar disk of the sun, enabling ‘Coronagraph’ to study the Sun’s corona or the surrounding atmosphere, for scientific observation.

The ‘Occulter’ spacecraft would line up in front of the other, around 150 metres away, to cast its shadow precisely onto the other. The shade provided by the first spacecraft (Occulter) would cover the fiery face of the Sun so that its faint surrounding ‘Coronal’ atmosphere becomes visible.

According to the European Space Agency, the corona is much hotter than the Sun itself and it is where space weather originates. It is also a topic of widespread scientific and practical interest.

Another significant aspect of Thursday’s mission is that the two satellites would fly as a ‘large rigid structure’ in space to provide formation flying technologies and rendezvous experiments.

The mission will demonstrate formation flying in the context of a large-scale science experiment.

The pattern of blocking the solar disk of the Sun occurs during solar eclipses and that too for a few minutes. However, the European Space Agency said, with Proba-3, the mission would be able to create “solar eclipses on demand.” The Bengaluru-based space agency would facilitate the mission by providing launch service, while scientists at the European Space Agency would perform scientific experiments to study the sun’s atmosphere.

For ISRO, this launch would provide key insights on taking up scientific experiments on the Sun after its maiden mission–Aditya-L1, which was successfully launched in September 2023.

The Proba-3 is a technology demonstration mission funded via the General Support Technology Programme.

The instruments onboard the satellites would travel closer to the solar rim for up to six hours at a time and each spacecraft would take up approximately a 19-hour orbit around the Earth.