Aditya-L1 has successfully accomplished the Halo-Orbit Insertion (HOI) at approximately 16:00 hrs on January 6, 2024 IST. The final phase of the maneuver involved firing of control engines for a short duration to put the solar observatory on its intentional orbit that 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.
L1 refers to Lagrange Point 1 of the Sun-Earth system. L1 is a location in space where the gravitational forces of two celestial bodies, here the Sun and Earth, are in equilibrium. Thus the satellite remains stable with respect to both the celestial bodies.
This specific Halo orbit has been selected to ensure a mission lifetime of 5 years, minimising station-keeping manoeuvres and thus minimising fuel consumption and ensuring a continuous, unobstructed view of sun.
The Lagrange point L1 for Aditya L1 Mission is 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 i.e. the study of the structure and dynamics of the Sun through its oscillations.
It is suitable for the "in situ" sampling of the solar wind and particles.
The success of this mission signifies ISRO's capabilities in such complex orbital manoeuvres also giving confidence to handle future interplanetary missions.