Aditya-L1 solar mission set for launch on Saturday from Sriharikota

The solar mission will be carried out by the Aditya-L1, which will be launched from the Sriharikota spaceport on the Isro’s workhorse rocket, the PSLV.

The Indian Space Research Organisation (Isro) announced on Monday that it will launch its first spacecraft to survey the Sun on September 2 at 11.50am, days after it created history by reaching close to the south pole of the Moon from where its Chandrayaan-3 has been sending the first readings about the atmosphere and the surface.

A graphic representation of ISRO’s Aditya L1 mission.

The solar mission will be carried out by the Aditya-L1, which will be launched from the Sriharikota spaceport on the Isro’s workhorse rocket, the PSLV, or polar satellite launch vehicle. After travelling 125 days to reach a distance of 1.5 million km from the Earth, it will stay put for an as yet unannounced duration of time.

“Aditya-L1 is the first space-based observatory-class Indian solar mission to study the Sun. The spacecraft is planned to be placed in a halo orbit around the Lagrangian point 1 (L1) of the Sun-Earth system, which is about 1.5 million km from the Earth,” said a document released by Isro detailing the project.

“A satellite placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation/eclipse. This will provide a greater advantage of observing the solar activities continuously. The spacecraft will carry seven payloads to observe,” it added.

HT reported on Saturday that September 2 was the likely launch date for the mission, with a broader window set for the September 1-5 period.

The mission is ambitious for several reasons — first, is the challenge of stationing a craft at a Lagrange point, which India has not done before.

There are five Lagrange points in space where gravity of the two closest objects in the solar system interact in such a way that a spacecraft placed at any of these will remain stable there (usually in a small orbit). Aditya-L1, as its name implies, will be stationed at the L1 point, the closest of the five Lagrange points, and also one from which an unhindered view of the Sun is possible.

Second, the nature of new insights that the spacecraft can bring. It will carry seven payloads, including four to observe the Sun’s outermost layers — known as the photosphere and chromosphere — by using electromagnetic and particle field detectors.

Among several objectives, it will study the drivers for space weather, including to better understand the dynamics of solar wind.

“The suit of Aditya-L1 payloads are expected to provide most crucial information to understand the problems of coronal heating, coronal mass ejection, pre-flare and flare activities, and their characteristics, dynamics of space weather, study of the propagation of particles, fields in the interplanetary medium, etc,” the agency’s document explained.

Studying these insights will help because the Sun affects many aspects on Earth, outside of just the sunlight. Flares, for instance, can cause radiomagnetic disturbances, and how these travel through the expanse of space too requires deeper understanding.

Speaking to news agencies on Monday, former Isro scientist Nambi Narayanan said: “This mission aimed at studying the Sun in close contact. Sun is the nearest star to Earth, and is a hot mix of helium and hydrogen about 150 million kms away from you. The findings of this mission will be significant.”

The United States’ agency Nasa and the European Space Agency (ESA) have previously placed orbiters to study the Sun, but India’s projects — like its others — will likely be significantly cheaper.

Among the way this will be done is by using the extremely reliable PSLV, in the XL configuration of the rocket — which is a more powerful version than the type typically used for satellite launches.

“Initially, the spacecraft will be placed in a Low Earth Orbit. Subsequently, the orbit will be made more elliptical and later the spacecraft will be launched towards L1 by using on-board propulsion. As the spacecraft travels towards L1, it will exit the Earths’ gravitational Sphere of Influence (SOI). After exit from SOI, the cruise phase will start and subsequently the spacecraft will be injected into a large halo orbit around L1. The total travel time from launch to L1 would take about four months for Aditya-L1,” said the agency in its mission document.