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 ...
David M. Perlman's user avatar
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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:
Mete's user avatar
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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 ...
TheMatrix Equation-balance's user avatar
5 votes
2 answers
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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. ...
Woody's user avatar
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6 votes
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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 ...
SpaceMatt's user avatar
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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-...
g_don'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
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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 ...
Dubukay's user avatar
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2 votes
2 answers
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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 ...
kardalos's user avatar
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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 ...
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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
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 ...
Suddhasattwa Ghosh 's user avatar
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2 answers
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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 ...
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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 ...
kardalos's user avatar
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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 ...
BradV's user avatar
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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 ...
kardalos's user avatar
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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 ...
kardalos's user avatar
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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 ...
Aabha Awere's user avatar
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1 answer
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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, ...
Sheldon's user avatar
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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 ...
NeutronStar's user avatar
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18 votes
4 answers
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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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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 ...
kardalos's user avatar
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4 votes
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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). ...
TrySCE2AUX's user avatar
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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 ...
Ken's user avatar
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24 votes
4 answers
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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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1 answer
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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 ...
Sheldon's user avatar
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23 votes
2 answers
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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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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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3 votes
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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 ...
Bruce Simonson's user avatar
7 votes
1 answer
834 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.
Harry Underbridge's user avatar
5 votes
2 answers
626 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 ...
Sunfish's user avatar
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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.
JEH's user avatar
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5 votes
1 answer
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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?
Ashvin's user avatar
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4 votes
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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 ...
user277093's user avatar
0 votes
1 answer
226 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?
Dims's user avatar
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11 votes
2 answers
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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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40 votes
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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
10 votes
2 answers
3k views

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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3 votes
1 answer
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How to calculate the Lagrangian points positions?

I have two bodies, one rotates around another on orbit. For i.e. Earth and Sun or Moon and Earth. If we know masses, velocity, distance and keplerian elements of orbit, how can we find the positions ...
Robotex's user avatar
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9 votes
2 answers
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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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26 votes
3 answers
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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
4 votes
2 answers
338 views

Can mascons have Lagrange-like points? In principle? At the Moon?

Background Lagrange points are a mathematical consequence of the The Circular Restricted Three Body Problem (CR3BP or CRTBP); two massive bodies orbiting around their center of mass and a third ...
uhoh's user avatar
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5 votes
2 answers
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In a 3D space defined by semimajor axis, eccentricity and inclination, what would be the shape of the space where SDP4 works better than SGP4?

@BillGray's answer to Why can't custom-made TLEs for the DSCOVR launch booster in orbit around Earth work with SDP4? is quite interesting and informative; I fail to do it justice by summarizing it as ...
uhoh's user avatar
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1 vote
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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 ...
Curtis Klein's user avatar
5 votes
3 answers
2k views

How do spacecraft reach Lagrange points?

As I understand, to reach a Lagrange point the spacecraft would need to slow down. Also, can spacecraft passing nearby Lagrange points get captured within the point?
Bruce Vici's user avatar
1 vote
2 answers
277 views

Why does it cost more to get to L4/5 than C3=0?

I was looking at Delta-V budgets and noticed that it costs 4.1 km/s to get from LEO to L4/5, but just 3.2 km/s for LEO to geocentric C3 = 0 (escape velocity). I find that counter-intuitive. Why does ...
Schwern's user avatar
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1 vote
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Spinning 16 Psyche at Mars L1 to envelop Mars with a magnetosheath?

16 Psyche is theorized to be the remnant iron core of an early small protoplanet that might have had it's surface and mantle stripped away through violent asteroid impacts. Some modeling of possible ...
Connor Garcia's user avatar
2 votes
1 answer
150 views

Travel time from lunar orbit (EML2) to Jupiter using skyhook only?

I am doing background research for a science fiction story, and hoping someone can help with this navigational question. Voyager 2 reached Jupiter from Earth in about 2 years. However (if I understand ...
Crystal E's user avatar
1 vote
0 answers
97 views

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 ...
John's user avatar
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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 ...
jrp's user avatar
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