Isro puts ESA’s Proba-3 in orbit; satellites to create solar eclipse experiment

Indian Space Research Organization (Isro) on Thursday successfully launched the European Space Agency’s (ESA) Proba-3 mission aboard the PSLV-C59 rocket, which lifted off from the first launch pad at Satish Dhawan Space Centre in Sriharikota.
In its 61st launch, the PSLV lifted off a little after 4pm as per a revised schedule — the mission was initially planned for Wednesday but postponed due to a propulsion system glitch in the satellite — and placed the satellite in the desired orbit more than 18 minutes thereafter.
The first acquisition of signal was expected by the flight control team at ESA’s ESEC establishment in Redu, Belgium, around a quarter of an hour after separation.
The latest member of ESA’s family of in-orbit demonstration missions, Proba-3 is, in fact, two spacecraft launched together in a dedicated commercial mission implemented by Space PSU NewSpace India Limited (Nsil).

Nsil CMD Radhakrishnan D told TOI from Sriharikota: “We’re delighted to have successfully accomplished the dedicated launch for ESA. This is the first time ever that the PSLV has placed a satellite in such a highly elliptical orbit with an apogee of nearly 60,500km. PSLV has again demonstrated its reliability and versatility in undertaking customer satellite missions in varied orbits.”
The satellites will, in orbit, separate to begin performing precise formation flying, precise to a single millimetre, about the thickness of an average fingernail.

“To prove their performance, Proba-3 has been devoted to an ambitious scientific goal. The pair will line up precisely with the Sun 150 m apart so that one casts a precisely controlled shadow onto the other,” ESA said.
By blocking out the fiery disc of the Sun, Proba-3’s ‘Occulter’ spacecraft will mimic a terrestrial total solar eclipse, to open up views of the Sun’s faint surrounding atmosphere, or ‘corona’, which is a million times fainter than its parent star. Proba-3’s second ‘Coronagraph’ spacecraft hosts the optical instrument that will observe the solar corona.
“On Earth, total solar eclipses only occur every 18 months on average, and last just for a few minutes. Solar scientists have to travel all over the world to take advantage of them. Proba-3 will be able to create solar eclipses on demand, observing closer to the edge of the Sun than any previous Earth- or space-based instrument, down to just 1.1 solar radii. And it will do so for six hours per 19-hour 36-minute orbit,” as per ESA.
Proba-3 will also perform general formation flying experiments including rendezvous, resizing the distance between the pair and joint retargeting. The aim is to achieve performance equivalent to a single virtual spacecraft measuring about 150 m across, demonstrating a novel method of operating missions in space, where instruments can be shared between multiple platforms.