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Aditya L1, India’s first mission to study the Sun, has taken images of itself as well as the Earth and the 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,” said the space agency in a tweet on Thursday morning.
The video posted by the Indian Space Research Organisation (ISRO) shows an image of a portion of the spacecraft captured by its on-board camera. It shows the Visible Emission Line Coronagraph (VELC) that will study the solar corona, including the very inner layers that haven’t been studied by other missions and the Solar Ultraviolet Imaging Telescope (SUIT) that will study the different layers of solar atmosphere in the shorter UV wavelengths that are not possible to detect from Earth.
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 to 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.
“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,” said a scientist from the space agency.
The scientist cited the example of the ESA/NASA mission called Solar and Heliospheric Observatory (SOHO) that 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, 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 onboard 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 of 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 Prof 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 surface.
