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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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Why are so many space telescopes placed in LEO instead of at Lagrange Points? And why do we hear about Hubble more than any Langrange-orbit telescope?

Here is the list of every space telescope launched by different space agencies - List of space telescopes. Most of the listed telescopes are placed in Lower Earth Orbit (about 95% of them). It's ...
Paran's user avatar
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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 ...
Oscar Smith's user avatar
37 votes
3 answers
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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 ...
Waffle's Crazy Peanut's user avatar
36 votes
3 answers
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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 ...
Chris Mueller's user avatar
34 votes
3 answers
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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 ...
gerrit's user avatar
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This orbit looks wrong near a Lagrange point. Is it?

On a completely unrelated forum, i came across the following graphic: The orbit seems wrong to me, especially the first curve. From the initial trajectory, I would expect the orbit to have been in a ...
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26 votes
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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 ...
TheEnvironmentalist's user avatar
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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 ...
diwhyyyyy's user avatar
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Why won't JWST deploy in LEO where it is potentially serviceable?

The James Webb Space Telescope will deploy (unfold mechanically) while on the way to L2. Couldn't it do so in LEO, where it is potentially serviceable? Starliner CST-100 and Dragon are planned to soon ...
LocalFluff's user avatar
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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 ...
Stilez's user avatar
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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 ...
gerrit's user avatar
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How deep is the force well of L4 and L5 Lagrangian Points of Earth-Sun set?

The Lagrangian Points are points in space, where the combination of gravitational pull of a set of two bodies and the centripetal force of orbiting one of them add up to zero. The special property of $...
SF.'s user avatar
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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 ...
Bruce Simonson's user avatar
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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 ...
Curious Layman's user avatar
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2 answers
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Is this what station keeping maneuvers look like, or just glitches in data? (SOHO via Horizons)

I've been enjoying the JPL Horizons web interface and after I discovered the incredibly extensive database associated with SOHO (Solar and Heliospheric Observatory, also see sohowww.nascom.nasa.gov) ...
uhoh's user avatar
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Halo vs Lissajous orbit: Which station-keeping strategy to select and when?

I'm looking for a comprehensive pros and cons of the two most commonly used station-keeping types of orbits used at libration points, Lissajous and halo orbits. When would one select one over the ...
TildalWave's user avatar
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Aren't the mirrors of the James Webb Space Telescope too unprotected?

I've looked at the design of the James Webb Space Telescope and I got curious about something, some years ago, it seems that the international space station was hit by micro-meteorites. I'm wondering ...
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Are Lagrange points stable over a long period of time?

Do Lagrange points ever move or are they on the same spot as long as the solar system exists in it's current form with all it's planets in its current order?. They could move due to orbital objects ...
bastik's user avatar
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Are some Halo Orbits actually Stable? (stable orbits about unstable Lagrange points)

update: some more sources; the broken site spacecraftforall.com/a-new-orbit used to have an interactive simulation, here's an old screen shot: Hat tip to @NgPh for finding this Space College page ...
uhoh's user avatar
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What are the sources of light at L2? How will the James Webb telescope be powered?

The James Webb space telescope will be positioned very close to L2. According to JPL, Webb will have a large solar-array to power itself. I don't understand how this works, since L2 is positioned "...
Daniel Kats's user avatar
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3 answers
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Why would a mission to Sun-Earth L1 have an instantaneous launch window?

I was watching the webcast for Falcon 9 Flight 15 (launching DSCOVR) when they scrubbed their first launch attempt due to some issues during the terminal countdown. Before the scrub, the narrator ...
Nate Barbettini's user avatar
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1 answer
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How does orbital eccentricity affect positions of Lagrange points $L_4$ and $L_5$?

It is often said that the $L_4$ and $L_5$ points are "60 degrees ahead and behind" a planet like Jupiter. Clearly this is true only in the case of circular orbits. In more elliptical orbits, I assume ...
ben's user avatar
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How many satellites can stay in a Lagrange point?

Lagrange points as I understand it are points in space between 2 objects where the gravitational pull between them is effectively equal. That makes station keeping at these points relatively easy. ...
David says Reinstate Monica's user avatar
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If something "falls off" the L2 or L1 point, where will it go?

The L1 and L2 points are thought to be unstable "saddle" points, meaning that there is stability in two directions of movement, but not in the other. That raises an obvious question - when a ...
AlanSE's user avatar
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Do we sufficiently understand mechanics of Lagrange point stationkeeping for EML2 rendezvous and assembly?

I've been watching some recorded videos from the April 22 - 24, 2014 Humans2Mars conference (videos and live streams, when available, are on the National Institute of Aerospace channel on Livestream), ...
TildalWave's user avatar
14 votes
2 answers
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Can the James Webb Space Telescope basically manage its own orbit if necessary?

In this great answer I learned that the Mars rover Curiosity can be given some tasks and it will go ahead and manage the work and navigation by itself, to at least a certain limit. The James Webb ...
uhoh's user avatar
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Are there interstellar Lagrange points?

Is there for example some L1 like libration point where the Hill spheres of the Sun and of the Alpha+Beta Centauri meet? And are Lagrange points between stars inside of a binary system, like Alpha and ...
LocalFluff's user avatar
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2 answers
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Ordering of the Lagrange points

Is there any basis for the ordering of the L-points? Specifically, is there any particular reason for choosing L1 as the first L-point?
user440337's user avatar
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Reverse Lunar Space Elevator

The possibility of a space elevator from the lunar surface is discussed in this question. A lunar elevator for the purpose of return to Earth could be achieved at the L1 Lagrange Point between Earth ...
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How Many Martian Lagrange points are there? ...And are they useful for satellites?

I know that the Sun-Earth system has 5 Lagrange points, and there are five more Earth-Moon associated Lagrange points; so ten in all that are in some way associated with the Earth. Since Mars has two ...
Rickest Rick's user avatar
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Are large halo orbits around L₁'s and L₂'s preferred over small orbits for reasons other than geometry?

There have been many examples of the placement of satellites in orbits around Lagrange points, most have been sun-earth and earth-moon $L_1$ and $L_2$ due to their proximity to earth. In each case ...
uhoh's user avatar
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11 votes
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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. ...
Roger Wood's user avatar
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Low Energy Transfer within Earth-Moon system

Practical aspects of a total low energy transfer to the Moon have been seen in missions like GENESIS, which uses Weak stability Boundary legs of Earth and Sun to reach ESL-2. This four body model ...
Kuldeep Barad's user avatar
10 votes
4 answers
687 views

Single-shot Blue Marble pictures

I was quite surprised to read in today's Earth Observatory Picture of the Day that the DSCOVR spacecraft, currently en route to the $L_1$ Lagrange point, will be the first spacecraft able to see the ...
E.P.'s user avatar
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10 votes
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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) ...
LocalFluff's user avatar
10 votes
2 answers
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The design of the halo orbit of the James Webb Space Telescope

As I feel a little less uncomfortable with "halo" orbits, with this question, I would like to explore the practical aspects, in particular those related to the design of the James Webb Space ...
Ng Ph's user avatar
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10 votes
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Are there propellant-less ways to balance at an unstable orbital point?

A station situated somewhere like EML-2 is really at an unstable point. I've heard of crafts using rocket firing to maintain that position in response to small deviations. Could you do this without ...
AlanSE's user avatar
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9 votes
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Stability of Lissajous orbits around Sun-Venus L1

How far is it from the Venus? Does Mercury gives too big perturbations for a stable Lissajous orbit?
Milkman's user avatar
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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 ...
jrp's user avatar
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9 votes
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How much mass can be put in an L4 or L5 and it still maintain reasonable stability?

Every explanation of Lagrange points I've seen refers to it as a sort of three-body solution, where one of the body's masses is taken to be comparatively negligible to make the solution work. However, ...
Connie's user avatar
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9 votes
1 answer
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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 ...
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What are reasons to put Gaia space telescope into L2 Lagrangian point of Sun-Earth system?

As I remember, Gaia (wiki, ESA) was planned to flight away from Earth, so it orbit is not LEO, and not GEO. It is located near 1.5 millions kilometers away from Earth, orbiting thousands kilometers ...
osgx's user avatar
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9 votes
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What is the flight plan to get Gaia in orbit around the Sun–Earth $L_2$ Lagrangian point?

Gaia is a planned European Space Agency's (ESA) space observatory that will aim to chart a three-dimensional map of our Galaxy, the Milky Way. It is planned to operate around the Sun–Earth $L_2$ (SEL2)...
Stu's user avatar
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9 votes
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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 ...
Kevin Kostlan's user avatar
9 votes
1 answer
453 views

What is the diameter of magnetopause 1.5 millions kilometers behind the Earth?

Earth has strong magnetic field, which changes concentration of charged particles from Sun near the planet. There is rather safe torus near the Earth (LEO non-polar orbits), and also there is long ...
osgx's user avatar
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8 votes
3 answers
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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?
LocalFluff's user avatar
8 votes
2 answers
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Does it even make sense to talk about Mercury's triangular libration points (L4, L5)?

The recent question How much radiation shielding would be required for a habitat at Mercury–Sun L5? got me thinking. There are a large number of disadvantages and challenges to building or putting a ...
uhoh's user avatar
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8 votes
2 answers
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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 ...
Everyone's user avatar
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8 votes
2 answers
546 views

For an EML-1 to Mars transfer orbit, would flying to the right or left of Earth be preferable?

If an L1 space station was used as a staging area for a mission to Mars, it looks like we would use the Oberth effect in a close flyby to Earth to make the burn. But I just realized - the idea, as ...
AlanSE's user avatar
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8 votes
1 answer
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Are there any man-made satellites at Lagrangian points?

There are 5 lagrangian points. Are there any man-made satellites at any of those points? Is there a reason for the presence or absence of satellites at these points?
Dale's user avatar
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