ISRO’S Aditya-L1 solar mission takes a selfie, images of Earth, Moon

The video shared by the Indian Space Research Organisation showed the image of one hemisphere of Earth illuminated by sunlight as well as a white speck that the agency pointed out was the Moon.

This "selfie" was taken by cameras aboard ISRO's Aditya L1 solar mission.

India’s first mission to study the Sun, Aditya-L1, has taken images of itself as well as the Earth and the distant moon from the highly elliptical orbit around the Earth where it is currently present. “Onlooker! Aditya-L1, destined for the Sun-Earth L1 point, takes a selfie and images of the Earth and the Moon,” the Indian Space Research Organisation (ISRO) said in a post on X, formerly Twitter, on Thursday morning.

The video posted by the space agency shows an image of a portion of the spacecraft captured by its onboard camera, showing two of the main science experiments being carried out by the mission. It shows the Visible Emission Line Coronagraph (VELC) that will study the solar corona including the very inner layers that have not been studied by other missions and the Solar Ultraviolet Imaging Telescope (SUIT) that will study the different layers of the solar atmosphere in the shorter UV wavelengths that are not possible to detect from Earth.

Aditya-L1 Mission:
👀Onlooker!

Aditya-L1,
destined for the Sun-Earth L1 point,
takes a selfie and
images of the Earth and the Moon.#AdityaL1 pic.twitter.com/54KxrfYSwy

— ISRO (@isro) September 7, 2023

The video also showed the image of one hemisphere of Earth illuminated by sunlight as well as a tiny white speck that the space agency had to point out was the Moon.

The spacecraft is currently undergoing a series of manoeuvres to raise its orbit as well as velocity till it can finally be slingshot towards the Sun. The spacecraft underwent the second such manoeuvre around the Earth on September 5, reaching an orbit of 282 km x 40,225 km. The next manoeuvre is set to take place on September 10 at 02.30 am. 

Once injected into the path towards the Sun, the spacecraft will take nearly four months to travel the 1.5 million kilometre distance to the L1 point that provides an unobstructed 24/7 view of the Sun. Although the planned mission life of Aditya-L1 is five years, it is likely to study the Sun for much, much longer.

“The beauty of the L1 or any other Lagrange point orbit is that the gravitational pull exerted by the two celestial bodies – in this case, the Sun and the Earth – exactly balance each other out. This means the spacecraft hardly needs any fuel to stay its course. Although Aditya-L1 has been designed for a five-year mission life, it can last as long as 25 years,” a scientist from ISRO said.

The scientist cited the example of the ESA/NASA mission called Solar and Heliospheric Observatory (SOHO) which was launched in 1995 as a two-year-long mission. It continues to sit at the L1 point and gather data on the Sun for over 27 years now.

Not only is the Aditya-L1 mission likely to last longer than intended, but the data its VELC instrument will provide is eagerly awaited by the SOHO team and the world as well. This is because one of the coronagraphs aboard SOHO that could look close to the inner corona was lost. The coronagraph on board Aditya L1, on the other hand, will be able to see much closer to the surface of the Sun than the SOHO coronagraph could, close to the point where the solar corona begins.

“To study the faint light coming from the corona, we need to artificially block the bright light from the photosphere or the surface of the Sun. The catch in doing that is we may not be able to block only the photosphere – the size of the occulting disk is usually bigger than the photosphere. If we assume the size of the photosphere to be 1 unit, the occulting disk has been 2 units for previous missions. For the first time with the Aditya-L1 mission we are trying to see as close as possible to the beginning of the corona with a smaller occulting disk that is just 1.05 times the photosphere,” said Professor R Ramesh from the Indian Institute of Astrophysics. The coronagraph on SOHO that was lost had an occulting disc of 1.1 times the radius of the sun’s surface.