Explained | As Aditya-L1 takes off, what will the payloads do?

Visible Emission Line Coronagraph (VELC), the prime payload onboard Aditya-L1, will view the Corona as close as possible from the disc of the Sun and study its dynamics through the emission line, while another payload Solar Ultra-violet Imaging Telescope (SUIT) will look at how the Sun’s atmosphere is coupled and the radiation gets absorbed in earth atmosphere.

Of the seven scientific payloads, four will directly view and study the Sun, while the remaining three will conduct in-situ studies of particles and fields around the L1 point. VELC, SUIT, Solar Low Energy X-ray Spectrometer and High Energy L1 Orbiting X-ray Spectrometer (SoLEXS & HE10S), Aditya Solar wind Particle Experiment and Plasma Analyser Package for Aditya (ASPEX & PAPA), and Magnetometer (MAG) were developed indigenously by ISRO and several institutions including Indian Institute of Astrophysics (IIA), Bengaluru.

Dr Annapoorni Subramaniam, Director, IIA, said VELC developed by IIA was designed as a reflective coronagraph with a multi-slit spectrograph which will see the Sun from the visible wavelength.

“The emission line will detect certain elements because the Corona is hot and the emission which you get doesn’t absorb the light which is coming from the Sun. We are tracking these lines using a coronagraph which makes a Total Solar Eclipse all the time within the instrument. By this, you are looking at the Sun all the time on a 24/7 mission,” Dr Subramaniam said.

She added the payload will see the Corona as close as possible from the disc of the Sun because Corona is a million times fainter than the disc of the Sun. The instrument will study the Corona and its dynamics and can measure the velocity by simple physics called the doppler effect through the emission line. “We can see how much matter is moving and how that matter will come down to the earth. It will not just carry out a holistic study of the Sun, but also of the heliosphere,” the IIA director said.

Dr Durgesh Tripathi, Principal Investigator for payload SUIT, said Aditya L1 will be at an orbit near the L1 point, while NASA’s James Webb Space Telescope (JWST) is on the other side, which is the L2 point. “Aditya L1 is a multi-wave satellite which observes all electromagnetic spectrum. SUIT will in particular look at the ultraviolet radiation and emissions from the lower and middle atmosphere of the Sun,” Tripathi, Professor, Inter University Centre for Astronomy and Astrophysics, Pune, said.

He added that the payload will look at how in general the Sun’s atmosphere is coupled, and how actually the radiation is coming down and getting absorbed in the earth's atmosphere.

SoLEXS & HE10S will study X-ray flares from the Sun over a wide X-ray energy range, while ASPEX & PAPA are designed to study the solar wind and energetic ions, as well as their energy distribution. Magnetometer (MAG) will measure interplanetary MAG magnetic fields at the L1 point.