The Aditya-L1 solar observatory spacecraft successfully executed its Halo-Orbit Insertion (HOI) at approximately 4:00 PM on January 6, 2024 (Indian Standard Time). This critical phase entailed a brief activation of the spacecraft’s control engines.
Aditya-L1 is now in a stable Halo orbit, situated about 1.5 million kilometers from Earth, along the dynamic line between the Sun and Earth. This orbit is unique for its three-dimensional path involving the Sun, Earth, and the spacecraft, taking approximately 177.86 Earth days to complete one orbit. The chosen orbit optimizes the spacecraft’s operational life to five years, reduces the need for frequent trajectory adjustments, saves fuel, and guarantees a consistent, clear view of the Sun.
The Aditya-L1 mission, an initiative of India, aims to continuously monitor and analyze the chromospheric and coronal activities of the Sun from the Lagrangian point L1. The advantages of situating Aditya-L1 in a Halo orbit around the L1 point, as opposed to a Low Earth Orbit (LEO), are significant. It offers a stable Sun-spacecraft velocity, which is crucial for helioseismology studies. Being outside Earth’s magnetosphere, it is ideal for direct sampling of solar winds and particles. Additionally, it facilitates uninterrupted observation of the Sun and ensures continual communication with Earth-based stations.
The process of Halo orbit insertion began as Aditya-L1 passed the XZ plane in the Sun-Earth-L1 rotating system, achieving the necessary orbital state. This maneuver was crucial for adjusting the spacecraft’s velocity components to align with the desired Halo orbit, with specific target dimensions for its three-dimensional path.
This phase was a pivotal moment in the mission, demanding precise control and navigation. The successful insertion reflects the Indian Space Research Organisation’s (ISRO) proficiency in executing complex space maneuvers and sets a confident precedent for future interplanetary missions.
Aditya-L1 was developed at the UR Rao Satellite Centre (URSC) with contributions from various ISRO centers and payloads from Indian scientific labs, IIA, IUCAA, and ISRO. Launched by PLSV-C57 on September 2, 2023, from SDSC SHAR, the spacecraft initially entered an elliptical parking orbit. It then embarked on its journey towards the Sun-Earth-L1 Lagrange point, gradually expanding its orbit through a series of liquid engine burns. The maneuver strategy was meticulously planned to minimize velocity increments while avoiding extensive exposure to the Van Allen radiation belts. Two trajectory correction maneuvers (TCM-1 and TCM-2) were executed to refine the spacecraft’s path in preparation for the HOI.
Following a 110-day cruise phase, all payloads were tested and found to be functioning satisfactorily.
Below is a graphical representation of the Halo orbit insertion process. It shows Aditya-L1’s trajectory from Earth to the L1 point and the TCM1 & TCM2 adjustments that steered the spacecraft into the Halo Orbit. The final engine firing on January 6, 2024, marked by a red dot, aligned the spacecraft with its target orbit. Without this HOI maneuver, the spacecraft would have continued on a different trajectory.
Source: https://www.isro.gov.in/halo-orbit-insertion-adtya-l1.html
