ADITYA-L1 spacecraft minutes before insertion into orbit by the terminal stage of PSLV-C57

Bangalore: Aditya L1 spacecraft, India's first space-based mission to study the Sun, during the early hours on Friday, underwent the fourth earth-bound manoeuvre successfully, ISRO said.

"The fourth Earth-bound manoeuvre (EBN#4) is performed successfully. ISRO's ground stations at Mauritius, Bangalore, SDSC-SHAR and Port Blair tracked the satellite during this operation, while a transportable terminal currently stationed in the Fiji islands for Aditya-L1 will support post-burn operations," the space agency said in a post on Twitter.

The new orbit attained is 256 km x 121973 km, it said: "The next manoeuvre Trans-Lagragean Point 1 Insertion (TL1I) -- a send-off from the Earth -- is scheduled for September 19, around 02:00 Hrs. IST." Aditya-L1 is the first Indian space-based observatory to study the Sun from a halo orbit around the first Sun-Earth Lagrangian point (L1), which is located roughly 1.5 million km from the Earth.

The first, second and third earth-bound manoeuvre was successfully performed on September 3, 5 and 10 respectively.

The manoeuvres are being performed during the spacecraft's 16-day journey around the Earth during which the spacecraft will gain the necessary velocity for its further journey to L1.

With the completion of four earth-bound orbital manoeuvres, Aditya-L1 will next undergo a Trans-Lagrangian1 insertion manoeuvre, marking the beginning of its nearly 110-day trajectory to the destination around the L1 Lagrange point.

Upon arrival at the L1 point, another manoeuvre binds Aditya L1 to an orbit around L1, a balanced gravitational location between the Earth and the Sun.

The satellite spends its whole mission life orbiting around L1 in an irregularly shaped orbit in a plane roughly perpendicular to the line joining the Earth and the Sun.

ISRO's Polar Satellite Launch Vehicle (PSLV-C57) on September 2 successfully launched the Aditya-L1 spacecraft from the Second Launch Pad of Satish Dhawan Space Centre (SDSC), Sriharikota.

After a flight duration of 63 minutes and 20 seconds that day, the Aditya-L1 spacecraft was successfully injected into an elliptical orbit of 235x19500 km around the Earth.

According to ISRO, a spacecraft placed in the halo orbit around the L1 point has the major advantage of continuously viewing the Sun without any occultation /eclipses.

This will provide a greater advantage in observing solar activities and their effect on space weather in real-time.

Aditya-L1 carries seven scientific payloads indigenously developed by ISRO and national research laboratories, including the Indian Institute of Astrophysics (IIA) in Bangalore and the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune.

The payloads are to observe the photosphere, chromosphere and the outermost layers of the Sun (the corona) using electromagnetic particle and magnetic field detectors.

Using the special vantage point L1, four payloads directly view the Sun and the remaining three payloads carry out in-situ studies of particles and fields at the Lagrange point L1, thus providing important scientific studies of the propagatory effect of solar dynamics in the interplanetary medium.

The suits of Aditya L1 payloads are expected to provide the most crucial information to understand the problem of coronal heating, coronal mass ejection, pre-flare and flare activities and their characteristics, dynamics of space weather, and propagation of particles and fields.

According to scientists, there are five Lagrangian points (or parking areas) between the Earth and the Sun where a small object tends to stay if put there. The Lagrange Points are named after Italian-French mathematician Joseph-Louis Lagrange for his prize-winning paper -- "Essai sur le Probleme des Trois Corps, 1772." These points in space can be used by spacecraft to remain there with reduced fuel consumption.

At a Lagrange point, the gravitational pull of the two large bodies (the Sun and the Earth) equals the necessary centripetal force required for a small object to move with them.