Linked Questions

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 ...
Waffle's Crazy Peanut's user avatar
16 votes
1 answer
5k views

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
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 ...
user avatar
4 votes
1 answer
3k views

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
11 votes
1 answer
3k views

What is the difference between halo orbits and Lissajous orbits?

The Wikipedia articles for halo orbit and Lissajous orbit leave me wondering how these two orbits are different from an orbital mechanical point of view. Could they be discussed together here, so I ...
uhoh's user avatar
  • 149k
14 votes
1 answer
2k views

What sort of orbital elements are used to describe halo orbits?

For standard orbits we can use Keplerian elements, TLE, or other similar. These don't make much sense for Halo orbits, which are not around a central body, but around a Lagrangian point, and follow an ...
SF.'s user avatar
  • 55.1k
13 votes
2 answers
640 views

Why is NASA choosing such a large “halo” orbit at L2 for JWST?

According to “https://webb.nasa.gov/content/about/orbit.html”, NASA plans to exploit a quarter million mile radius “halo” orbit at L2. And Webb will orbit around L2, not sit stationary precisely at ...
Bob Buxton's user avatar
4 votes
2 answers
294 views

Comet at Mars L1

If we placed and maintained a comet at Mars L1 point would we get a coma and tail that would add volatiles to the Martian atmosphere? I've also read comets create a bow shock with the solar wind, ...
Brooks Nelson's user avatar
5 votes
1 answer
1k views

Why is Queqiao's dish antenna so big? (Chang'e-4 relay satellite) Largest ever on/near the Moon?

Source: Chinese language blogpost The NASA Spaceflight article Queqiao relay satellite launched ahead of Chang’e-4 lunar mission describes the communications relay satellite that will be used to ...
uhoh's user avatar
  • 149k
4 votes
0 answers
2k views

How do Falcon-9's cold gas thruster maneuvers account for the center of mass changes due to "floating fuel shifts"?

The Art of Engineering video How SpaceX Lands Rockets with Astonishing Accuracy after 07:19 explains: Cold Gas Thrusters The falcon 9 is equipped with a total of ...
uhoh's user avatar
  • 149k
4 votes
1 answer
388 views

Station-keeping delta-v per year for an Earth-Moon vanilla halo orbit?

This answer reminds us that an Earth-Moon L1 or L2 vanilla1 halo orbit remaining always visible to some patch on the Moon's surface requires station-keeping. Queqiao uses such an orbit having ...
uhoh's user avatar
  • 149k
2 votes
1 answer
220 views

Is communication from a spacecraft in SEL1 disturbed by the Sun?

A spacecraft at the Sun Earth Lagrange point one (1% of an AU, or one Solar diameter, from Earth towards the Sun) would have the Sun as its background. Is the Sun emitting strongly enough at ...
LocalFluff's user avatar
1 vote
1 answer
264 views

What is the darkest orbit around Earth?

What orbits around Earth has the least and most sun light exposure? I wondered: When taking pictures either of Earth or otherwise with various telescopes in orbit, does it help to be in Earth's ...
Muze's user avatar
  • 1
3 votes
1 answer
261 views

Was Queqiao in a halo or Lissajous orbit? Why do sources disagree?

Wikipedia's Lissajous orbit says that sources disagree on the nature of Queqiao relay satellite's orbit; if it was in a proper halo orbit or just a Lissajous orbit. Proper halo orbits have the same ...
uhoh's user avatar
  • 149k