Aditya - L1(Spying Sun)

Aditya - L1(Spying Sun)

Halo-Orbit Insertion (HOI) of its solar observatory spacecraft, Aditya-L1 was accomplished at 16.00 Hrs (approx) on January 6, 2024 (IST).

The Aditya-L1 spacecraft was launched by PLSV-C57 on September 2, 2023 from SDSC SHAR, into an elliptical parking orbit (EPO) of 235.6 km by 19502.7 km. From here, Aditya-L1 embarked on an extraordinary journey towards the Sun-Earth-L1 Lagrange point, with the help of the onboard propulsion system, increased its orbital size progressively and moved toward L1 point. Five liquid engine burns (LEB) were executed during Earth orbit phase; gradually raised the apogee of the EPO in order to attain the desired trajectory with the fifth burn, known as the trans-L1 injection (TL1I) maneuver. The maneuver strategy is carefully devised to minimize incremental velocity addition (ΔV) for reaching the target L1 halo orbit while restricting the number of perigee passes to minimize the spacecraft's exposure to the high radiation Van Allen radiation belts. To address errors during, TL1I phase, a short burn of the engines, called TCM-1 was conducted on October 5, 2023, and another TCM-2 on December 14, 2023 to ensure compliance with Halo orbit insertion condition parameters. The spacecraft underwent a cruise phase lasting approximately 110 days to achieve the present condition prior to HOI targeted on January 6, 2024.

Halo-Orbit (Lagrange point) are those unique points in space where the gravitational forces of celestial bodies balance out.

If we consider Sun & Earth we get 5 Lagrange points.

The orbit of Aditya-L1 spacecraft is located roughly 1.5 million km from earth on the continuously moving Sun – Earth line with an orbital period of about 177.86 earth days. This specific halo orbit is selected to ensure a mission lifetime of 5 years, minimising station-keeping manoeuvres and thus fuel consumption and ensuring a continuous, unobstructed view of sun.

The Aditya-L1 mission is an Indian solar observatory at Lagrangian point L1 for “Observing and understanding the chromospheric and coronal dynamics of the Sun” in a continuous manner. Placing the Aditya-L1 in a halo orbit around L1 point has advantages as compared to placing in a Low Earth Orbit (LEO):

It provides a smooth Sun-spacecraft velocity change throughout the orbit, appropriate for helioseismology.

It is outside of the magnetosphere of Earth, thus suitable for the "in situ" sampling of the solar wind and particles.

It allows unobstructed, continuous observation of the Sun, and view of earth for enabling continuous communication to ground stations.

UR Rao Satellite Centre (URSC) with participation from various ISRO centres designed Aditya-L1.

 The payloads onboard Aditya-L1 were developed by Indian scientific laboratories, IIA, IUCAA and ISRO.