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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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36 votes
3 answers
18k views

Is there a lot of space trash at the Earth-Moon Lagrange points?

Lagrange points are the points in a multi-body gravitational system in which the gravitational force and centrifugal force sum to zero. The image below from this Wikipedia article shows the 5 ...
25 votes
5 answers
3k views

Delta-v to hit the moon: is reaching Lunar L1 enough?

Lot of questions involve shooting things into the Sun. But there are no aliens on the Sun: they are on the Moon. I want to drop things on them, but since there's lot of them, I can just drop a ...
3 votes
0 answers
92 views

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 ...
11 votes
2 answers
298 views

Why are Jupiter's trojans even remotely stable?

The spacecraft Lucy is en route to explore Jupiter's trojan asteroids. Lucy is so named because the trojan asteroids are believed to be fossil remnants from the formation of the solar sytem. ...
2 votes
1 answer
228 views

Why Euclid's orbit is not like Gaia but like JWST?

Euclid, Gaia and JWST are all orbiting Lagrange Point L2. Why is Euclid's orbit similar to JWST but not Gaia's, why is Gaia's orbit different than Euclid and JWST ? Orbits are shown here for example:
9 votes
1 answer
798 views

For how long do the various earth-moon lagrangian points receive sunlight each month?

Every month the earth-moon lagrangian points must be in the shade of the moon for some time For L1 and L3 probably on new moons, for L2 probably on full moons, and for L4 and L5 maybe when the moon ...
5 votes
4 answers
367 views

Would it be practical to position a telescope like JWST at Sun-Earth L4 or L5?

During a discussion of Lagrange points I was asked why we didn't put JWST at SE L4 or L5 since they are less unstable than L2. I thought a bit and came to think that the Earth gravity driven Halo ...
1 vote
1 answer
144 views

How do "halo orbits" save on propellent (delta-v)?

I am trying to understand what advantage the satellite's 'Halo Orbit' has compared to LEO or Geostationary orbits. "Lagrange points have proven to be very useful indeed since a spacecraft can be ...
6 votes
5 answers
2k views

Help with fictional scenario: trapped in Lagrange Point orbit

I'm a full-time screenwriter trying to create a realistic sci-fi scenario, though not necessarily a hyper-realistic one like those in The Martian. Think more along the lines of pseudo-scientific ...
5 votes
2 answers
234 views

What use (if any) does the "empty focus" of an elliptical orbit have in orbital mechanics?

The 2 bodies in a 2-body system orbit around their common barycenter, which is located at the common primary focus of both their orbits. The empty foci don't seem to have a job in celestial mechanics. ...
9 votes
1 answer
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How do the Moon and other planets affect Earth-Sun Lagrange points' locations?

We can calculate Earth-Sun Lagrange points based on Sun & earth mass/gravity. However moon and other planets must be affecting the location of these points. How this effect is analyzed and exact ...
2 votes
0 answers
49 views

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-...
9 votes
1 answer
320 views

If James Webb goes "over the hill" is it gone for good?

James Webb is in a Halo orbit around Earth's L2 point. It is in a gravitational saddle: two directions are stable ("up-down" and "front-back"). The "in-out" direction is ...
0 votes
0 answers
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Can the JWST look at Earth? What would it see? [duplicate]

There's a few questions on the site about whether we can see the James Webb Space Telescope from Earth (i.e. here and here), but I'm wondering about the opposite - can we see Earth using the JWST? I ...
2 votes
2 answers
251 views

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 ...
4 votes
1 answer
209 views

Radio Telescope / DSN Node in L4 and/or L5

Deploying really big radio dishes in space seems to be possible and "frequently" done with SIGINT satellites in geosynchronous orbit (like the assumed specs of the Orion satellite class). ...
6 votes
2 answers
384 views

Can JWST come in for a pit stop? Is the fuel supply on JWST adequate for a transfer to an Earth Moon libration point to allow repairs?

The James Webb Space Telescope is generally considered to be in an unserviceable location at SEL2. If servicing becomes necessary, is it possible for the JWST to use a low energy heteroclinic transfer ...
0 votes
0 answers
223 views

What is the distance between Mars and the lagrange point L2 Mars Sun? [duplicate]

I am writing a science fiction novel that is more soft that hard sci fi but I would like to know at least an estimat of the distances between L2 Mars Sun and Mars. I know that asking for an exact ...
8 votes
3 answers
1k views

What determines the orbital speed around a Lagrange point?

What value of M should I use to calculate the speed of a satellite orbiting a Lagrange point where there exists no mass?
10 votes
3 answers
978 views

How could transfers between SEL1&2 and EML Lagrange points be utilized?

The Earth has 7 Lagrange points nearby since SEL1 and SEL2 (Sun-Earth Lagrange points 1 and 2, respectively) are only between 3 and 5 LD (lunar distances) away from the five EML (Earth-Moon Lagrange) ...
8 votes
2 answers
2k views

Can a whole planetary system have Lagrangian points?

Wikipedia says: The Lagrange points mark positions where the combined gravitational pull of the two large masses provides precisely the centripetal force required to orbit with them The major bulk ...
4 votes
1 answer
128 views

How much margin does JWST have for station keeping in Halo orbit?

How much margin in $\frac{m}{s}$ does JWST have for station keeping in Halo orbit? JWST must always stay on the earth side of the L2 saddle since thrusters only point towards the sun. Also` solar ...
5 votes
1 answer
298 views

Has JWST done its first station keeping yet?

Has JWST done its first station keeping yet? The last burn I know about was the MCC2 burn on Jan24; more than 21 days ago; and that was a pretty long burn with a $\Delta v$ of 1.6 m/sec or 160 cm/sec, ...
18 votes
7 answers
4k views

Is there something inherently more difficult about servicing satellites in the 2nd Sun-Earth Lagrangian point?

There are several questions already asked on here about the potential for servicing the James Webb Space Telescope. This question asks what happens if the JWST needs repair. Basically, there are no ...
7 votes
5 answers
3k views

Gravitational field of the Moon and Earth

Is there any method to find a point or plane in space where the gravitational field of the Moon and Earth are the same? And if so, what happens to a spacecraft if it passes through that point or ...
2 votes
2 answers
562 views

Burns for EML-1 to LLO

Wikipedia gives 0.64 or 0.65 km/s for going from LLO to EML-1 or back. I would like to know what the delta v of the specific burns involved are, and if my initial calculations are close, I don't see ...
18 votes
4 answers
3k views

Does the distance to L2 vary?

Discussion of Lagrange point L2 and the JWST seem to be dropping out of the news cycle, so I thought I should ask this question while the topic is still warm. The distance of L2 for the sun/earth two ...
1 vote
0 answers
124 views

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 ...
3 votes
0 answers
134 views

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 ...
23 votes
3 answers
3k views

Are there any (Lagrange) points in the Solar System in perpetual shade?

This answer mentioned thermal cycling made me think of this question: Are there any points in the solar system, such as Lagrange points, where a spacecraft could reside in perpetual shade, protected ...
2 votes
1 answer
220 views

Is there any software or other resources that can find optimal launch windows and gravity assist trajectories involving Lagrange points?

I've been using GMAT to make various trajectories involving the Sun-Earth L2 point. Earth-L2-Mars, Earth-L2-Earth flyby-Mars, etc. However, the main source of optimal launch windows I've been using is ...
2 votes
0 answers
129 views

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 ...
2 votes
0 answers
53 views

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 ...
3 votes
1 answer
549 views

Code to generate Sun-Earth L2 halo orbits for given epoch?

I am working on a GMAT script out of personal interest (not part of a job) that involves a spacecraft orbiting the Sun-Earth L2 point. I have found some orbital state vectors for the spacecraft that ...
34 votes
3 answers
9k views

What does the Sun-Earth-Moon system look like from the Sun-Earth L-2 point?

The L-2 point of the Sun-Earth system is away from the Earth on the night-side of the Earth; i.e. it's always local midnight at the sub-satellite point. This is an attractive property for some ...
3 votes
0 answers
104 views

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 ...
1 vote
0 answers
83 views

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 ...
23 votes
2 answers
4k views

Since L2 has no visible marker, how will James Webb's ground control determine its relative position and velocity for station keeping?

James Webb will be in a halo orbit, station keeping around the Sun-Earth L2 point. This means it needs to monitor its position with regard to L2, for periodic station keeping purposes. But L2 isn't an ...
3 votes
1 answer
139 views

L2 for JWST - EM barycenter used in calculation?

I’ve been reading up on two and three body dynamics, wrt to L2 for the JWST. Are the calculations for this L2 based on the sun/earth masses and locations, or on the sun/(earth+moon barycenter) masses ...
37 votes
3 answers
10k views

Why should the James Webb Space telescope stay in the unstable L2?

We all know that James Webb Space telescope is planned to be launched in 2018. It has been decided that the orbit of JWST will be elliptical around the Lagrange point L2, which has been declared as ...
6 votes
2 answers
956 views

How does gravity change beyond L2?

Why does gravity appear to increase again on the far side of L2 from earth as indicated on the gravitational contour diagram? One would expect gravity to continue to decrease as the distance from sun ...
7 votes
1 answer
866 views

What are the characteristics of JWST's orbit around L2?

I'm particularly interested in the size of the elliptic, but also its eccentricity and whether it will be coplanar with Earth's ecliptic plane.
7 votes
3 answers
3k views

What is the required burn to keep a satellite at a Lagrangian point?

When a satellite reaches a Lagrangian point, it has a non-zero velocity $v_1$ because of the transfer orbit in which it had already been. What burn, say, $\Delta v$, one needs if the satellite is ...
5 votes
1 answer
908 views

What is the delta v required for insertion to sun-earth L2?

What is the delta v required to place a satellite in L2 from earth transfer orbit ( Like the James Webb Telescope )? Does orbits closer to L2 different delta v from orbits far from L2?
3 votes
0 answers
61 views

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.
4 votes
1 answer
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Is L2 at a distance where the Earth totally eclipses the Sun?

What is the furthest from the Earth that still offers a total eclipse of the Sun? Is L2 inside that distance? (I assume so due the the halo orbit that is planned but perhaps there are numerous other ...
0 votes
1 answer
227 views

How can back shield of JWST be 85-100 degrees Celsius hot if it will be in Earth's shadow?

I have heard, that back shield of James Webb space telescope will be as hot as 85-100 degrees of Celsius. But how can it be, if it will be in Earth's shadow in L2?
1 vote
1 answer
636 views

L2 point in multi-moon system

For an SF novel, if there were two large moons orbiting a planet, let's say one moon the size of Earth's moon and the 2nd moon about 20% larger, and the planet roughly the size of the Earth, would the ...
26 votes
3 answers
6k views

What is the "mass" of a Lagrange point?

Of the five Lagrange points, L4 and L5, as stable points, can be orbited by asteroids, satellites, and any other useful or interesting object. Assuming two-body motion however, calculating orbits with ...
40 votes
2 answers
5k views

Why doesn't JWST use ion thrusters?

Since the L2 point is unstable, JWST needs engines to maintain its orbit. It uses mono-propellant engines which have given it a 5-year minimum lifespan. Why weren't ion engines used instead? Wouldn't ...