43 votes
Accepted

Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission?

From the JWST Mission Operations Concept Document Some families of Lissajous orbits can result in the spacecraft crossing the line connecting the two bodies. In the Sun-Earth orbit, this can result ...
David Hammen's user avatar
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23 votes
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James Webb telescope; limits to propellant lifetime?

For some background see this answer to Could JWST stay at L2 "forever"? this answer to What happens to JWST after it runs out of propellant?. From the 2nd linked answer (slightly edited): ...
uhoh's user avatar
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22 votes
Accepted

Is this what station keeping maneuvers look like, or just glitches in data? (SOHO via Horizons)

You are most likely seeing an artifact of how JPL represents its ephemerides for fast numerical computation. JPL integrates the equations of motion over time. This inevitably results in mismatches ...
David Hammen's user avatar
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20 votes
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What happens to JWST after it runs out of propellant?

This Northrop Grumman video (starting at 09:31) illustrates JWST's orbit in a non-rotating (normal) frame. It's really in an orbit around the Sun about 1% farther ...
uhoh's user avatar
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19 votes
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Could JWST stay at L2 "forever"?

According to Wikipedia, the delta-v requirements to stay at L1 or L2 are about 30-100 m/s per year. That seems quite high, however, more likely is around 5-16 m/s. The sun shield has an area of about ...
PearsonArtPhoto's user avatar
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19 votes

Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission?

tl;dr: despite having to drain its batteries to run its electronics heaters, it might survive a short eclipse, but since the mission can easily designed to be eclipse free it's simply good practice to ...
uhoh's user avatar
  • 149k
18 votes

Why aren't energy and momentum (of a restricted three-body system) conserved, or are they?

In a two body system the total energy, the sum of kinetic energy and potential energy is constant for each body. If the total energy is constant for each body, the total energy for the whole system is ...
Uwe's user avatar
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17 votes
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What is a near rectilinear halo orbit?

Halo orbit families exist near the L1, L2, and L3 librations points. This video focuses on the L1 and L2 halo families. There are northern and southern families at each of the libration points. The ...
Diane's user avatar
  • 674
16 votes
Accepted

How would you identify when an object in a Lissajous orbit needs station keeping?

Halo orbits and their cousins Lissajous orbits (like the one DSCOVR is in) around the Sun-Earth L1 and L2 have periods of about a half-year. They are not generally stable and they want to "unwind&...
uhoh's user avatar
  • 149k
13 votes

Are large halo orbits around L₁'s and L₂'s preferred over small orbits for reasons other than geometry?

There are several reasons why spacecraft are sent into pseudo-orbits (they aren't actually "orbits") about the unstable Lagrange points. The least important reason is that only one spacecraft can be ...
David Hammen's user avatar
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13 votes

James Webb telescope; limits to propellant lifetime?

The telescope trajectory changes direction for halo orbit insertion. Image source: https://jwst-docs.stsci.edu/jwst-observatory-hardware/jwst-orbit Such a large change of direction would require a ...
Uwe's user avatar
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12 votes
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What is the required burn to keep a satellite at a Lagrangian point?

What is the required burn to keep a satellite at a Lagrangian point? tl;dr: typical station keeping delta-v for a halo orbit around Sun-Earth L1 or L2 points are of the order of 2 to 4 meters/sec per ...
uhoh's user avatar
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12 votes
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How frequent are (or will be) JWST station keeping burns at L2?

How frequent are (or will be) JWST station keeping burns at L2? 21 or 42 days I've heard mention of 'every 21 days' which at first look seems excessive but on second look may not be nuts if very ...
uhoh's user avatar
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11 votes
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What is the difference between halo orbits and Lissajous orbits?

Halo orbits are a sub-class of Lissajous orbits. So that image showing a simple circular-ish orbit is just showing a 1:1 Lissajous pattern. These Lagrange-point orbits are really orbiting around the ...
uhoh's user avatar
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11 votes
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Why is a near rectilinear halo orbit proposed for LOP-G (formerly known as Deep Space Gateway?)

In fact, they are the preferred option among other staging orbits by analyzing multiple factors: EARTH ACCESS: A study considering NASA SLS and Orion performances was carried out. Since SLS places ...
Julio's user avatar
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11 votes

How well is JWST doing on maintaining its Halo orbit?

Only partial: Not directly answering since it seems ok: Can only find up to 2022: Orbit around L2 is maintained through regular station-keeping burns, which are scheduled every three weeks. As of ...
blobbymcblobby's user avatar
10 votes
Accepted

Can the James Webb Space Telescope basically manage its own orbit if necessary?

I don't have too much time to research as I'm about to head off to work, but a quick investigation of the JWST doesn't show anything that could be used for Astrogation. Curiosity can do its own ...
UIDAlexD's user avatar
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9 votes
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What sort of orbital elements are used to describe halo orbits?

tl;dr: For a given pair of bodies in circular orbits around their center of mass, there are two symmetric families ("Northern" and "Southern") of proper halo orbits associated with ...
uhoh's user avatar
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8 votes

Could JWST stay at L2 "forever"?

This paper by Heiligers et al. explores Earth-moon libration point orbits with the addition of solar sail thrusting. While it is of course not directly translateable to Sun-Earth L2 (JWST) the ...
Alexander Vandenberghe's user avatar
8 votes

Can the James Webb Space Telescope basically manage its own orbit if necessary?

Short answer is no--JWST does not manage its orbit corrections itself. Stationkeeping is done from the ground. During normal ops ,there are both medium-gain and high-gain antennas on the sun side, ...
sohowsgoing's user avatar
8 votes
Accepted

How does a butterfly orbit move in 3D? Way to generate or visualize?

Sorry that I'm so late to this, but I worked with the butterfly family quite a lot when I was a student in Professor Howell's group so I feel compelled to answer! It looks like you found some good ...
Matt B's user avatar
  • 741
8 votes

Why are eclipses of the James Webb by the Earth or Moon not permitted during the mission?

"Power and thermal" but no further details. Earth and Moon eclipses pose significant hazards to the power and thermal subsystems. Source: LIBRATION ORBIT ECLIPSE AVOIDANCE MANEUVER STUDY ...
Organic Marble's user avatar
7 votes
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How to best think of the State Transition Matrix, and how to use it to find periodic Halo orbits?

The State Transition Matrix (STM) The STM is a linearization procedure of a dynamical system. It can be used for any non-linear dynamical system and is used to approximate the dynamics of a system ...
ChrisR's user avatar
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7 votes
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Why put X-ray telescope Spektr-RG/eROSITA all the way out at Sun-Earth L2?

eRosita is on its way to an elliptical orbit around L2 (with L2 in the centre of the ellipse). (image source: https://www.slideshare.net/esaops/wilms, p. 19) According to Merloni et al. (2012, https:/...
samcarter_is_at_texnique.fr's user avatar
7 votes

Are there some three-body orbits that can't be escaped? Can we know without propagating forever?

There are really two questions here: Do there exist $n$-body systems with long-term stability? Can a third body (massive or not) be shown, a-priori, to be bounded or to escape—without resorting to ...
geometrian's user avatar
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7 votes

The design of the halo orbit of the James Webb Space Telescope

Has the JWST halo orbit been chosen from a stable halo "template", and in "broad terms", what were the trade-offs between JWST's scientific mission requirement, orbital life-time ...
uhoh's user avatar
  • 149k
7 votes
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What are "transcritical, pitchfork, period-doubling, torus, and subharmonic bifurcations" in the context of three-body orbits? (e.g. butterflies)

I can attempt an answer by summarizing some of my favorite dissertations. Forgive some of the word vomit below, this is certainly not the most elegant or succinct explanation. I'll give a bit of a ...
Matt B's user avatar
  • 741
7 votes

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

Surely a significant reason is that L4 and L5 are much farther away, roughly 150 million km vs 1.5 million. That makes things more difficult in a number of ways, but probably the biggest is that ...
Mark Foskey's user avatar
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6 votes

Could JWST stay at L2 "forever"?

tl;dr: I think there could be room to do this. However, I don't think a conclusive answer can be had through analyses of magnitudes on envelope-backs. A real answer would only come from even more ...
uhoh's user avatar
  • 149k
6 votes
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What is the period of halo/Lissajous orbits?

As the halo orbits grow out of plane, their orbital periods generally decrease. You can see a plot of the period (in days) of the L1 and L2 halo families at the Moon as a function of the closest ...
Diane's user avatar
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