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# Questions tagged [lagrangian-points]

Lagrangian points (also Lagrange points, L-points, or libration points) are the five positions (L1 - L5) surrounding two celestial bodies where gravitational pull of the two large mass bodies provides the centripetal force required to orbit them. Such points are usually nominally unstable but somewhat periodic around celestial systems with stable orbits.

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### How bad is a non-Lagrangian Point orbit?

I am no expert on space physics, just an interested amateur. I've been searching for a few weeks and having a hard time gaining insight on this question. Phrasing the question more specifically: how ...
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### Porkchop plots/launch windows for Sun-Earth L2 to Mars transfers?

I've been using Earth-Mars launch windows, found with NASA's Trajectory Browser and EasyPorkchop, as launch windows from the Sun-Earth L2 Lagrange point to Mars, with the logic that since the L2 point ...
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### Why does the hot side of the JWST vary so much?

Usually the a sensor is in the low $50s$, yesterday it was $38^\circ C$, and today it is $55^\circ C$. Was it a measuring/reporting anomaly or does it really change that much? Here is the link to ...
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### How is the moon's orbital motion accounted for in determining the best observation platform/location for JWST at L2?

The moon's periodic motion would appear to impose a perturbation to the otherwise equilibrium state of the solar/earth L2 point.
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### What does the term "libration point gateway" mean?

In the Circular Restricted Three Body Problem, natural paths exist between periodic orbits or the libration points that have negligible cost. These are commonly known as free transfers between ...
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### What is the substantial difference between transit orbits and manifold trajectories in the frame of circular restricted three body problem?

In my MSc thesis I faced the problem of unstable hyperbolic invariant manifold trajectories (UHIMs) emanating from planar Lyapunov orbits around two collinear Lagrange points L1 and L2 of the Sun-...
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### What is this figure I have obtained from this MATLAB code around Earth-Moon Lagrange point 2?

This is part of the code I used, where EM: Earth moon ...
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### Which spacecraft have entered lunar orbit through L1?

I'm examining entering lunar orbit through the Earth-Moon L1 point with low-thrust propulsion. As part of this, I'm interested in all examples of spacecraft (both actually flown and ones that didn't ...
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### What is the radiation level at the L2 Mars-Sun point?

This answer shows that the radiation levels at the L2 Mars-Sun point will be lower because it lies within Mars' solar umbra. So what will the level of radiation be at the L2 Mars-Sun point? Also, how ...
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### Details about traveling from EM-L2 to SE-L1

Would the optimal time to launch be when the Moon was on the opposite side of the Earth from the Sun? What direction would be optimal leaving EM-L2, radially away from the moon? Is the last line of ...
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### How easy would it be to detect a large 400x1000 meters tubular habitat at L4

I'm writing an SF book and want to know if a 400 by 1000 meter tubular habitat at Lagrange point 4 (or L5) would be easily detected from earth?
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### What is a "synodic frame"? Can one be defined for an elliptical orbit?

A description of a "synodic frame" was one of the main ingredients in this excellent answer to a question about an animation of a funky-looking orbit that several different and distinctly interesting ...
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### How does one design a trajectory involving a lunar and Earth flyby and Lagrange points? What tools are used to calculate the initial guesses?

I'm trying to design a trajectory that takes a spacecraft from Sun-Earth L2 to a lunar flyby, to an Earth flyby and then to Mars (two flybys might be too complex, I might just do one). I've optimized ...
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### More advanced alternatives to Trajectory Optimization Tool?

I've been using Arrowstar's Trajectory Optimization Tool to plan interplanetary transfers, and it works well. The next thing I want to do is plan gravity assists from the Sun-Earth L2 Lagrange point ...
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### Parameters of the L2 insertion burn to be done tomorrow

What parameters control the impulse to be applied in the L2 insertion burn? What parameters control when/where it is to be performed? What velocity is the impulse applied to achieve? Is the vehicle ...
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### Earth-Sun decayed L1 to L4 transfer

Assume CR3BP (Circular Restricted 3-Body Problem) where a satellite occupies the Earth-Sun L1 point. The satellite dies, stops station-keeping, experiences a small perturbation (minimal effect on ...
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### How is it possible to connect trajectories at a Poincare section using the "bisection" method?

When constructing a heteroclinic connection (a connection between two different periodic orbits at two different libration points), the stable and unstable manifolds of two different libration points ...
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### When will DSCOVR appear too close to the Sun for reliable downlinking?

DSCOVR is in a Lissajous orbit about the Sun-Earth L2 point. That the orbit is called Lissajous rather than halo means that it's periods of horizontal libration and vertical libration are not equal. ...
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