James Webb Space Telescope

Discussion in 'Astronomy, Exobiology, & Cosmology' started by geordief, Dec 24, 2021.

  1. geordief Valued Senior Member

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    Another mouse sized step for the JWST

    "
    Most Recently Completed:
    Aft Deployed Instrument Radiator"

    Seems something is always going right these days

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    Last edited: Jan 7, 2022
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  3. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Good news

    Also I just checked and almost ¾ way there

    Found out can change the default distance and temperature measurements from miles / fahrenheit to kilometres / centigrade

    Opens with miles / fahrenheit but tap the ol' English<>Metric and it switches to the setting it stored on your device

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  5. geordief Valued Senior Member

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    Both wings locked in place.

    Think they adjust the 18 individual mirrors next(last steps before entering orbit at L2?)
     
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  7. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Just checked. Seems at this moment it is a tad short of ¾ distance on the way to destination

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  8. geordief Valued Senior Member

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    Well ,it will be very reassuring when they have covered that last quarter and bivvied up for the night.
     
  9. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    As long as we don't spot any Aliens wearing mask when telescope starts operations

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    There is a camping ground out there?

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  10. geordief Valued Senior Member

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    Don't think they have planning permission yet.
     
  11. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Don't think anyone going to jet out there to issue fine

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  12. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    According to my calculations now past the ¾ mark at 341+ kilometres

    See screenshot

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    Sliding scale at bottom difficult to gauge

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  13. geordief Valued Senior Member

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    But only about half way there time wise.

    I wonder why.Is there a long deceleration or does docking take a hell of a lot of maneuvering ?
     
  14. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Guess with weight being a critical factor with most launches scientists calculated the minimum speed (as slow as possible) telescope would be and fuel requirements needed to obtain best orientation without wasting fuel slowing the craft down

    Let the travel time do that

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  15. Michael 345 New year. PRESENT is 72 years oldl Valued Senior Member

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    Just added app to new mobile. App details much sharper. Yah

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  16. James R Just this guy, you know? Staff Member

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    My guess would be that the gravity of the Earth and the Moon is probably slowing it down. Not enough for it to stop in the L2 orbit, though: it will need an orbital insertion burn for that.

    edited to add: actually, I think the insertion burn is probably needed to increase its speed relative to the Sun. Otherwise it would continue on an elliptical orbit and fall back towards the Earth.
     
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  17. exchemist Valued Senior Member

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    Also, they need to get it into an orbit around L2 perpendicular to the plane of the ecliptic.
     
  18. James R Just this guy, you know? Staff Member

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    Yes, it will be orbiting around L2. I don't think the orbit is perpendicular to the ecliptic, though. (I wonder if it's at the Earth's tilt angle...)
     
  19. billvon Valued Senior Member

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    Neither. It's coasting now, and gravity is still slowing it down. It should arrive at a few hundred MPH, and will require one last firing of its engine to stop it.

    Fun fact - at the "turnover" point on the Apollo missions (where the Moon's gravity took over from the Earth's) the spacecraft was only doing 300mph.
     
  20. exchemist Valued Senior Member

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    I thought it had to be perpendicular to take advantage of the gravity well around L2. As I understand it, any motion along the radius of the earth's orbit, i.e. along the extension of the line joining the sun and earth, will be unstable and cause it to move even further in that direction. So it will be metastable if it is perpendicular and even then corrections will be required as it will have a tendency to drift in or out along that radial direction.

    But it is interesting and I may have misconstrued what they are going to do. The gravity field around L2 is not that straight forward to understand.
     
  21. foghorn Registered Senior Member

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    A 19 second video clip shows it will orbit ''perpendicular'' to plane of the ecliptic.
    The NASA article says Webb will orbit around L2 once every six months and that orbit is roughly the same size as the Moon's orbit about the Earth.
    See the very short first video on this page:
    https://webb.nasa.gov/content/about/orbit.html

    Quotes from that page:
     
    Last edited: Jan 10, 2022
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  22. exchemist Valued Senior Member

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    Yes, that's what I thought. However it doesn't explain the bit about the metastability of an orbit around L2.
     
  23. geordief Valued Senior Member

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    No cake yet ,but already we have the icing

    "JWST: A very interesting update from Mike Menzel, NASA mission systems engineer: thanks to the accuracy of the Ariane 5 launch and two ultra-precise trajectory correction burns, Webb should have enough propellant, roughly speaking, to operate "around 20 years;" exact numbers TBD"

    https://mobile.twitter.com/cbs_spacenews/status/1479909293189173249
     

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