The Indian Space Research Organisation (ISRO) achieved a significant milestone with the successful completion of the Halo-Orbit Insertion (HOI) for the Aditya-L1 solar observatory spacecraft on January 6, 2024. This critical maneuver, involving precise navigation and control, was executed at approximately 16:00 Hrs (IST).
The Aditya-L1 spacecraft now orbits in a periodic Halo orbit situated around 1.5 million km from Earth along the Sun-Earth line, with an orbital period of about 177.86 earth days. This specific orbit, selected for its advantages, ensures a mission lifetime of 5 years, minimizes station-keeping maneuvers, reduces fuel consumption, and allows for a continuous, unobstructed view of the Sun.
The Aditya-L1 mission focuses on “Observing and understanding the chromospheric and coronal dynamics of the Sun” from the Lagrangian point L1. Placing the spacecraft in a Halo orbit around L1 offers distinct advantages over a Low Earth Orbit (LEO):
Smooth Sun-Spacecraft Velocity Change: Ideal for helioseismology, the Halo orbit provides a consistent Sun-spacecraft velocity change throughout the orbit.
Outside Earth’s Magnetosphere: Positioned outside the magnetosphere, Aditya-L1 is suitable for “in situ” sampling of the solar wind and particles.
Uninterrupted Sun Observation: The Halo orbit allows continuous observation of the Sun and provides an unobstructed view of Earth for seamless communication with ground stations.
Halo Orbit Insertion Process:
The insertion process initiated as the spacecraft crossed the XZ plane in the Sun-Earth-L1 rotating system. The maneuver involved nullifying the X and Z velocity components and attaining the required Y-velocity for the Halo orbit. The specific Halo orbit parameters for Aditya-L1 are Ax: 209200 km, Ay: 663200 km, and Az: 120000 km.
This successful insertion represents a critical phase demanding precise navigation, constant monitoring, and adjustments of the spacecraft’s speed and position using onboard thrusters. ISRO’s achievement not only showcases its expertise in complex orbital maneuvers but also instills confidence for future interplanetary missions.
Aditya-L1, designed at UR Rao Satellite Centre (URSC), features payloads developed by Indian scientific laboratories, including IIA, IUCAA, and ISRO. Launched on September 2, 2023, aboard PSLV-C57, Aditya-L1 embarked on a journey towards the Sun-Earth-L1 Lagrange point, progressively increasing its orbital size with five liquid engine burns during the Earth orbit phase. Two trajectory correction maneuvers (TCM-1 and TCM-2) were conducted to ensure compliance with Halo orbit insertion conditions.
As Aditya-L1 enters this new phase, all payloads have been tested and confirmed to perform satisfactorily. The successful Halo-Orbit Insertion not only advances solar observations but also positions India as a formidable player in space exploration. The red dot in the graphic below signifies the accomplishment of the HOI condition on January 6, 2024, a moment marked by minimum fuel consumption. The final firing aligned the spacecraft with the Halo Orbit, a critical maneuver ensuring optimal mission conditions. Without the HOI, the spacecraft would have followed a different trajectory marked in the graphic.
