The successful accomplishment of the Halo-Orbit Insertion of Aditya-L1 has been achieved.

 

The successful accomplishment of the Halo-Orbit Insertion of Aditya-L1 has been achieved.

credits image: ISRO India Solar mission: Aditya-L1

On January 6, 2024, the Halo-Orbit Insertion (HOI) of the Aditya-L1 solar observatory spacecraft was successfully completed at approximately 16.00 Hrs (IST). The final phase of the maneuver involved a brief firing of the control engines.

credits image: ISRO India Solar mission: Aditya-L1 successfully enters final orbit

 

The Aditya-L1 spacecraft is positioned in a periodic Halo orbit, located around 1.5 million km from Earth on the Sun-Earth line, which is constantly in motion. Its orbital period is approximately 177.86 earth days. This specific Halo orbit is a three-dimensional orbit involving the Sun, Earth, and the spacecraft. It has been chosen to ensure a mission lifetime of 5 years, minimizing the need for station-keeping maneuvers and reducing fuel consumption, while also providing a continuous and unobstructed view of the Sun.

India creates yet another landmark. India’s first solar observatory Aditya-L1 reaches it’s destination. It is a testament to the relentless dedication of our scientists in realising among the most complex and intricate space missions. I join the nation in applauding this…

— Narendra Modi (@narendramodi) January 6, 2024

 

The Aditya-L1 mission is an Indian solar observatory situated at Lagrangian point L1, with the purpose of observing and understanding the dynamics of the Sun's chromosphere and corona in a continuous manner. Placing the Aditya-L1 in a Halo orbit around L1 offers several advantages over placing it in a Low Earth Orbit (LEO):

 

1. It provides a smooth change in velocity between the Sun and the spacecraft throughout the orbit, which is ideal for helioseismology.

2. It is located outside of Earth's magnetosphere, making it suitable for "in situ" sampling of the solar wind and particles.

3. It allows for uninterrupted and continuous observation of the Sun, as well as a clear view of Earth for continuous communication with ground stations.

 

The process of Halo orbit insertion began as the spacecraft crossed the XZ plane in the Sun-Earth-L1 rotating system, with the required orbital state. The insertion maneuver is crucial in nullifying the X and Z velocity components and achieving the necessary Y-velocity in the L1 rotating frame to enter the desired Halo orbit. The targeted Halo orbit for Aditya-L1 has semi-axes of Ax: 209200 km, Ay: 663200 km, and Az: 120000 km (refer to the figure for a visual representation).

The successful insertion of Aditya-L1 into its designated Halo orbit was a critical phase of the mission, requiring precise navigation and control. Constant monitoring and adjustments to the spacecraft's speed and position were made using onboard thrusters. This achievement not only demonstrates ISRO's capabilities in complex orbital maneuvers but also instills confidence in handling future interplanetary missions.

 

Aditya-L1 was developed at UR Rao Satellite Centre (URSC) with contributions from various ISRO centers. The scientific payloads onboard Aditya-L1 were developed by Indian scientific laboratories, IIA, IUCAA, and ISRO. The spacecraft was launched on September 2, 2023, by PLSV-C57 from SDSC SHAR, initially placed in an elliptical parking orbit (EPO) with dimensions of 235.6 km by 19502.7 km. From there, Aditya-L1 embarked on an extraordinary journey towards the Sun-Earth-L1 Lagrange point, gradually increasing its orbital size and moving towards the L1 point using its onboard propulsion system. During the Earth orbit phase, five liquid engine burns (LEB) were executed to raise the apogee of the EPO and achieve the desired trajectory. The fifth burn, known as the trans-L1 injection (TL1I) maneuver, was crucial for reaching the target L1 halo orbit while minimizing the spacecraft's exposure to the high radiation Van Allen belts. To address any errors during the TL1I phase, two short engine burns, TCM-1 and TCM-2, were conducted on October 5, 2023, and December 14, 2023, respectively, to ensure compliance with the Halo orbit insertion condition parameters. Following a cruise phase of approximately 110 days, the spacecraft reached its present condition prior to the targeted Halo orbit insertion on January 6, 2024.

 

All the payloads underwent testing during the pre-commissioning phase, and their performance has been confirmed to be satisfactory.

 

Please refer to the picture below.

 

credits image: ISRO India Solar mission: Aditya-L1

credits image: ISRO India Solar mission: Aditya-L1.