The insertion of Aditya-L1 into this Halo orbit presents a critical mission phase, demanding precise navigation and co TVntrol. A successful insertion further involves constant monitoring along with the adjustment of the spacecraft's speed and position using onboard thrusters. The success of this insertion not only signifies ISRO's capabilities in such complex orbital manoeuvres but also gives confidence in handling future interplanetary missions.
Aditya-L1 was designed and realized at UR Rao Satellite Centre (URSC) with participation from various ISRO centres. The payloads onboard Aditya-L1 were developed by Indian scientific laboratories, IIA, IUCAA, and ISRO. The Aditya-L1 spacecraft was launched by PSLV-C57 on 2nd September 2023 from SDSC SHAR into an elliptical parking orbit (EPO) of 235.6 km by 19,502.7 km. From here, Aditya-L1 embarked on an extraordinary journey towards the Sun-Earth-L1 Lagrange point, with the help of the onboard propulsion system, progressively increasing its orbital size and moving toward the L1 point. Five liquid engine burns (LEB) were executed during the Earth orbit phase, gradually raising the apogee of the EPO to attain the desired trajectory. The fifth burn, known as the trans-L1 injection (TL1I) manoeuvre, carefully devised the strategy to minimize incremental velocity addition (ΔV) for reaching the target L1 halo orbit while restricting the number of perigee passes to minimize the spacecraft's exposure to the high radiation Van Allen radiation belts. To address errors during the TL1I phase, a short burn of the engines, called TCM-1, was conducted on 5th October 2023, and another TCM-2 on 14th December 2023 to ensure compliance with Halo orbit insertion condition parameters. The spacecraft underwent a cruise phase lasting approximately 110 days to achieve the present condition before the Halo Orbit Insertion (HOI) targeted on 6th January 2024.
All the payloads were tested during the pre-commissioning phase, and the performance of all the payloads is confirmed to be satisfactory.
The picture below shows the Halo orbit insertion process graphically in a two-dimensional picture. The Aditya-L1 spacecraft was moving from Earth towards the L1 point in the direction of the Sun. The TCM1 & 2 firing oriented the spacecraft toward the Halo Orbit, making it reach the HOI condition (which is a minimum fuel consumption condition) on 6th January 2024 (Marked by the red dot). The final firing was done at this point, making the spacecraft align with the Halo Orbit. If the HOI manoeuvre was not conducted as done today, the spacecraft would have moved in the direction marked (Without HOI).
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