In a groundbreaking achievement, the Indian Space Research Organisation (ISRO) has accomplished the Halo-Orbit Insertion (HOI) for the Aditya-L1 solar observatory spacecraft on January 6, 2024, around 4:00 PM (IST).
Aditya-L1 now gracefully moves in a looping Halo orbit situated approximately 1.5 million km away from Earth along the Sun-Earth line. This specially chosen orbit, circling the Sun every 177.86 earth days, guarantees a mission life of 5 years, reduces the need for frequent adjustments, conserves fuel, and ensures an uninterrupted view of the Sun.
The primary mission of Aditya-L1 is to watch and understand the Sun’s chromospheric and coronal dynamics from the Lagrangian point L1. Opting for a Halo orbit instead of a Low Earth Orbit (LEO) offers unique advantages:
Steady Sun-Spacecraft Speed Change: The Halo orbit maintains a consistent change in speed between the Sun and the spacecraft, making it ideal for studying solar vibrations (helioseismology).
Beyond Earth’s Magnetic Influence: Positioned outside Earth’s magnetic field, Aditya-L1 is perfect for directly sampling the solar wind and particles.
Uninterrupted Sun Gazing: The Halo orbit enables continuous observation of the Sun and provides an open view of Earth, facilitating seamless communication with ground stations.
Journey to Halo Orbit:
The process of entering the Halo orbit began as the spacecraft crossed the XZ plane in the Sun-Earth-L1 rotating system. This intricate maneuver involved balancing the spacecraft’s velocity in different directions to attain the needed velocity for the Halo orbit. The specific parameters for Aditya-L1’s Halo orbit are Ax: 209200 km, Ay: 663200 km, and Az: 120000 km.
This successful insertion marks a crucial phase that demanded precise navigation, continuous 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, crafted 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 toward the Sun-Earth-L1 Lagrange point, progressively expanding its orbit with five liquid engine burns during the Earth orbit phase. Two trajectory correction maneuvers (TCM-1 and TCM-2) were executed to ensure compliance with Halo orbit insertion conditions.
As Aditya-L1 enters this new phase, all payloads have been meticulously tested and confirmed to perform satisfactorily. The successful Halo-Orbit Insertion not only advances solar observations but also positions India as a significant player in the realm of space exploration. The graphic below visually captures the accomplishment of the HOI condition on January 6, 2024, symbolized by the red dot, signifying minimum fuel consumption. The final firing aligned the spacecraft with the Halo Orbit, a pivotal maneuver ensuring optimal mission conditions. Without the HOI, the spacecraft would have followed a different trajectory, as illustrated in the graphic. This achievement underscores India’s commitment to advancing scientific exploration beyond our planet’s boundaries.
