On Saturday, ISRO is set to execute the final maneuver that will position India’s Aditya-L1 space probe into a halo orbit—an orbit around the Sun-Earth Lagrange Point 1 (L1), approximately 1.5 million kilometers away from Earth. By firing a group of thrusters for a brief period, tentatively concluding around 4 pm on that day, the probe will settle into its intended destination.
Aditya-L1, launched on September 2, embarked on its journey toward L1 on September 18. This Lagrange point represents a stable region where the gravitational forces between the Earth and the Sun, along with centrifugal force, achieve equilibrium.
Upon arrival at L1, India’s satellite will join four active probes, three of which are solely managed by NASA—WIND, Advanced Composition Explorer (ACE), and Deep Space Climate Observatory (DSCOVR). The fourth probe, the Solar and Heliospheric Observatory (SOHO), is a collaborative mission between NASA and the European Space Agency (ESA).
M. Sankaran, director of the UR Rao Satellite Centre (URSC), stated, “The final maneuver will be brief, utilizing a group of thrusters from Aditya-L1’s twelve. The selection of thrusters, whether the liquid apogee engine (LAM) or others, will be determined based on the spacecraft’s position on Saturday.”
Equipped with seven instruments to study the Sun and solar storms, Aditya-L1 aims for a planned five-year mission, leveraging L1’s unobstructed view of the Sun.
However, reaching L1 is only half the challenge; maintaining the orbit is equally demanding. ISRO relies on precise “orbit determination” procedures, involving mathematical algorithms and specialized software developed by URSC, to track the spacecraft’s position accurately.
ISRO chairman S. Somnath emphasized, “Upon reaching L1, periodic maneuvers will be performed to maintain the spacecraft in its intended orbit.”
Sustaining position at L1 presents challenges, as highlighted by the European Space Agency (ESA). L1 is categorized as an ‘unstable’ Lagrange point, necessitating spacecraft to orbit around it, treating the point akin to an ‘invisible planet.’ Continuous ‘station keeping’ maneuvers, approximately monthly, become imperative to retain the correct orbit due to the inherent instability and the rapid growth of trajectory errors.
Somnath previously acknowledged the mild but persistent instability at L1, noting it as preferable compared to the difficulties posed by L3 and L4. He cautioned that without meticulous orbit determination, the spacecraft could deviate from its intended path.
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ISRO set to place Aditya-L1 in its final orbit on this day; check details
