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Thread: How Can the WebbTelescope Orbit L2?

  1. #1 How Can the WebbTelescope Orbit L2? 
    exchemist
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    I have read the James Webb telescope will "orbit" the 2nd Lagrange point rather than just sitting at it exactly. How can it do that since, far from there being no net attraction towards that point, there is in fact a tendency for objects to drift away from it, i.e. a sort of net repulsion effect?

    And why do the telescope operators apparently not want it to sit directly at L2 itself?


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    Forum Masters Degree Double Helix's Avatar
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    Quote Originally Posted by exchemist View Post
    I have read the James Webb telescope will "orbit" the 2nd Lagrange point rather than just sitting at it exactly. How can it do that since, far from there being no net attraction towards that point, there is in fact a tendency for objects to drift away from it, i.e. a sort of net repulsion effect?

    And why do the telescope operators apparently not want it to sit directly at L2 itself?

    Had not read about this. Thanks for the info. And it is a substantial orbit!

    Quoting from the link below (1):

    "And Webb will orbit around L2, not sit stationary precisely at L2. Webb's orbit is represented in this screenshot from our deployment video (below), roughly to scale; it is actually similar in size to the Moon's orbit around the Earth! This orbit (which takes Webb about 6 months to complete once) keeps the telescope out of the shadows of both the Earth and Moon. Unlike Hubble, which goes in and out of Earth shadow every 90 minutes, Webb will have an unimpeded view that will allow science operations 24/7."

    end quote

    The means for maintaining this orbit will apparently be small, periodic thruster burns (2).

    Quoting from (2):

    "Lagrange points are sometimes nicknamed "parking" spots for spacecraft, as they mark locations where the gravitational tugs of different bodies balance out. However, throughout its stay at L2, Webb will need to conduct occasional small thruster burns for "station keeping" and "momentum management" to retain its proper location and orientation in space."

    end quote

    It seems the orbit around L2 provides for longer locks on faint, distant objects, allowing for continuous, uninterrupted light acquisition. One imagines a Webb "Deep Field" could take many days, as would faint exoplanets.

    The telescope also has more fuel than expected due to the perfect launch trajectory of the Ariane 5 rocket. Again, praise be to ESA and CSA! (It is a religious experience for some of us!)


    "Webb Orbit"

    1. https://webb.nasa.gov/content/about/orbit.html


    "James Webb Space Telescope has enough fuel for way more than 10 years of science"

    2. https://www.space.com/james-webb-spa...-fuel-lifetime


    Last edited by Double Helix; December 30th, 2021 at 10:18 PM.
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