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ESA Support To Aditya-L1
ESA is supporting Aditya-L1 in two ways: the Agency is providing deep space communication services to the mission, and, last year, ESA assisted ISRO with the validation of important new flight dynamics software.
Communication is an essential part of every space mission. Without ground station support, it’s impossible to get any science data from a spacecraft, to know how it’s doing, to know if it is safe or even to know where it is.
“ESA’s global network of deep space tracking stations and use of internationally recognised technical standards allows us to help our partners track, command and receive data from their spacecraft almost anywhere in the Solar System,” says Ramesh Chellathurai, ESA Service Manager and ESA Cross-Support Liaison Officer for ISRO.
ESA is the main provider of ground station services for Aditya-L1. ESA stations will support the mission from beginning to end: from the critical ‘Launch and Early Orbit Phase’, throughout the journey to L1, and to send commands to and receive science data from Aditya-L1 for multiple hours per day over the next two years of routine operations.
Lagrange Point 1 – A Perfect Home For Solar Explorers
The 5 Lagrange points of the Sun-Earth system.Aditya-L1 will operate from a halo orbit around L1
Getting There
This manoeuvre will be performed soon after launch, as the amount of fuel required to achieve the necessary trajectory grows quickly with time. Aditya-L1 will first perform manoeuvres to adjust its orbit around Earth after launch, before performing a transfer manoeuvre to L1. The spacecraft will reach L1 approximately 100 days after launch.
Staying There
L1 is one of the ‘unstable’ Lagrange equilibrium points. Keeping a spacecraft exactly at the L1 point is practically impossible.
Instead, spacecraft enter orbit around L1 as if the Lagrange point were an ‘invisible planet’. Even so, due to the instability of this orbit, small trajectory errors will grow quickly. As a result, spacecraft must perform ‘station keeping’ manoeuvres roughly once a month to keep them in the correct orbit.
An inability to perform these monthly manoeuvres can be a big problem. In June 1998, the SOHO mission experienced an issue and failed to carry out its station keeping. The error in its orbit grew so quickly and so unpredictably that contact was lost with the spacecraft, and it began drifting into the void.
A combined team of NASA and ESA experts set to work to safely recover the spacecraft, eventually finding it far from its expected position and re-establishing contact. 25 years later, SOHO is still in orbit around L1 and returning valuable scientific data.
It’s Not Just Orbits That Come Full Circle
For some of ESA’s flight dynamics experts, this exercise felt familiar. As ESA prepared to launch its own early deep space missions, it faced similar challenges to those ISRO faces today. ESA reached out to a team from NASA’s Jet Propulsion Laboratory (JPL) to help validate the interplanetary orbit determination software for ESA’s Mars Express mission and for the comet chaser, Rosetta, both of which were then successfully navigated by ESA. The exercise was similar in scope and goal to the one carried out by ESA and ISRO for Aditya-L1 last year.
The International Space Community
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