You can have a look at this, a practical example.RobbyQ said:TL;DR Summary: What is the accuracy of parking craft into Lagrange points
I often wonder what the accuracy is when dealing with spacecraft and wondered how accurate a craft needs to be positioned into the Lagrange (L1,L2,L3) positions. Are we talking plus or minus 1km/100km/1000km etc. It's just that the system is so vast and what instruments are used to achieve a good L sweet spot?
Those three Lagrange points are unstable, so there is a trade-off between staying close versus the fuel required to stay there. (L4 and L5 are stable). A big consideration is whether sunlight is needed for power. L2 is in the shadow of the Earth. JWST stays near, but orbiting the L2 Lagrange point so that its solar cells will get sunlight. The distance of JWST from the L2 point varies between 250,000 to 832,000 km. (see this). If you think that is a lot, remember that the Sun is over 100 million km away.RobbyQ said:TL;DR Summary: What is the accuracy of parking craft into Lagrange points
I often wonder what the accuracy is when dealing with spacecraft and wondered how accurate a craft needs to be positioned into the Lagrange (L1,L2,L3) positions. Are we talking plus or minus 1km/100km/1000km etc. It's just that the system is so vast and what instruments are used to achieve a good L sweet spot?
Wow that's crazy. It actually orbits the L2FactChecker said:Those three Lagrange points are unstable, so there is a trade-off between staying close versus the fuel required to stay there. (L4 and L5 are stable). A big consideration is whether sunlight is needed for power. L2 is in the shadow of the Earth. JWST stays near, but orbiting the L2 Lagrange point so that its solar cells will get sunlight. The distance of JWST from the L2 point varies between 250,000 to 832,000 km. (see this). If you think that is a lot, remember that the Sun is over 100 million km away.
Yes. It is roughly following the Earth's orbit but it is farther from the Sun than the Earth is. My understanding is that the combined gravity of the Sun and Earth (the component in the direction of the Sun) balance the centrifugal force of its orbit around the Sun so that part is in balance. Then it can essentially orbit the Earth at an offset distance around L2 (since there is a component of Earth gravity pointing toward L2). The orbit is a little unstable so it takes small corrections occasionally. There is a lot more to it that I am not knowledgeable enough to comment on.RobbyQ said:Wow that's crazy. It actually orbits the L2
Thanks. This video I found very interesting too as it discusses the component forces leading up to the JWST orbit around L2. And even this is simplified.FactChecker said:Yes. It is roughly following the Earth's orbit but it is farther from the Sun than the Earth is. My understanding is that the combined gravity of the Sun and Earth (the component in the direction of the Sun) balance the centrifugal force of its orbit around the Sun so that part is in balance. Then it can essentially orbit the Earth at an offset distance around L2 (since there is a component of Earth gravity pointing toward L2). The orbit is a little unstable so it takes small corrections occasionally. There is a lot more to it that I am not knowledgeable enough to comment on.
RobbyQ said:Thanks. This video I found very interesting too as it discusses the component forces leading up to the JWST orbit around L2. And even this is simplified.
I agree . Very informative. Also what's interesting (about 5mins into video) is that they keep it slightly Earth side of L2 so it has tendency to fall Earth wards and so the thrust burners to correct it back towards L2 are always Sun facing so as not to have to turn it around and get burnt up.FactChecker said:That is a great video! Thanks!
Euclid joined L2 too last month.RobbyQ said:I agree . Very informative. Also what's interesting (about 5mins into video) is that they keep it slightly Earth side of L2 so it has tendency to fall Earth wards and so the thrust burners to correct it back towards L2 are always Sun facing so as not to have to turn it around and get burnt up.
A Lagrange point is a location in space where the combined gravitational forces of two large bodies, such as the Earth and the Moon, create a region of equilibrium for a smaller object. There are five such points, labeled L1 through L5, where a spacecraft can theoretically remain stationary relative to the two larger bodies.
Parking a spacecraft at a Lagrange point requires a high degree of accuracy, typically within a few kilometers. This precision ensures that the spacecraft remains within the stable region of the Lagrange point, where gravitational forces balance out and allow for minimal fuel consumption to maintain position.
To achieve the necessary accuracy, spacecraft use a combination of advanced navigation systems, including star trackers, gyroscopes, and ground-based tracking. Additionally, precise thrusters and continuous monitoring and adjustments from mission control are essential to maintain the spacecraft's position.
Yes, there have been several successful missions that parked spacecraft at Lagrange points. Notable examples include the Solar and Heliospheric Observatory (SOHO) at L1 and the James Webb Space Telescope (JWST), which is planned to be positioned at L2. These missions demonstrate the feasibility and effectiveness of parking spacecraft at these points.
Maintaining a spacecraft at a Lagrange point presents several challenges, including the need for continuous monitoring and occasional adjustments to counteract perturbations from other gravitational forces, solar radiation pressure, and other space weather effects. Additionally, the precise initial insertion into the Lagrange point is critical to minimize fuel consumption and ensure long-term stability.