Aditya-L1 Mission: Completion of First Halo Orbit

By R Anil Kumar

• The spacecraft, which was inserted into orbit on January 6, underwent three station-keeping manoeuvres on February 22, June 7, and July 2 to counteract perturbing forces and ensure its transition into the second halo orbit

• Aditya-L1’s journey around the Sun-Earth L1 point requires precise planning and understanding of various forces that could alter its trajectory. By studying these forces, ISRO could accurately plot the spacecraft’s path and plan necessary adjustments. Tuesday’s manoeuvre successfully used ISRO’s advanced flight dynamics software, as illustrated in a chart provided by the agency

• The Aditya-L1 mission aims to study the Sun’s upper atmosphere, focusing on the chromosphere and corona. Its objectives include investigating heating mechanisms, ionised plasma physics, coronal mass ejections (CMEs), and flares

• The mission is designed to observe the particle and plasma environment, examine solar corona physics, diagnose plasma properties, study the development of CMEs, measure magnetic fields in the corona, and investigate space weather drivers like the solar wind

Bengaluru, July 2. Aditya-L1 spacecraft has completed its first halo orbit around the Sun-Earth L1 point. The Aditya-L1 mission is an Indian solar observatory at Lagrangian point L1, launched on September 2, 2023 and was inserted in its targeted halo orbit on January 6, 2024. Aditya-L1 spacecraft in the Halo orbit takes 178 days to complete a revolution around the L1 point.

During its travel in the halo orbit, Aditya-L1 spacecraft will be subjected to various perturbing forces that will cause it to depart from the targeted orbit. It underwent two station-keeping manoeuvres on February 22 and June 7, respectively, to maintain this orbit. Today’s 3rd station-keeping manoeuvre has ensured that its travel continued in to the second halo orbit path around L1.

This journey of Aditya L1 around Sun-Earth L1 Lagrangian point involves modelling of complex dynamics. The understanding of various perturbing forces acting on the spacecraft helped in determining the trajectory accurately and planning precise orbit manoeuvres. With today’s manoeuvre, the state-of-the-art flight dynamics software developed in-house at URSC-ISRO for the Aditya-L1 missions stands fully validated.

The blue trajectory, in the figure, is the orbit around the Lagrangian point L1. This trajectory is a 3 dimensional trajectory, and what is shown is the projection of it in the X-Y plane. SK# 1, 2 & 3 are the Station Keeping manoeuvres by the Aditya-L1 spacecraft.

The final firing of the thrusters, I e.SK# 3 on July 2, placed the spacecraft back in the required orbit. If an accurate firing was not done, the spacecraft would have moved away in a trajectory shown in green colour. The X-Y axes are marked in distance of km, with Lagrangian point L1 at the origin.

(Images Source: ISRO)