JAMES WEBB SPACE TELESCOPE LAUNCH LIVE

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In order to be kept cool the telescope is going to be positioned way out at the far L2 point which is four times further out than the moon. It's not going to orbit the earth as the moon does , it will orbit perpendicularly about the L2 point which is just weird and takes some getting your head around as it's going to orbit at right angles to the earths orbital plane around an empty point in space with no body of mass to provide gravitational attraction. So what keeps it in orbit ? It's apparently something to do with the interaction between the earth and the suns mass but I don't pretend to understand how that works.

Also being so far out, if anything goes wrong with the deployment and folding out of the heat shield or mirror they are stuffed as no repair mission is planned to be possible as it was for Hubble.

File:Animation of James Webb Space Telescope trajectory - Polar view.gif - Wikipedia
 

whitenemesis

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This explains the Lagrangian points

 
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This explains the Lagrangian points

 

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Love this stuff, don't understand it all but very interesting.
Finding things out there every day, let's see what they find with this one.
Let's hope it all goes well 🤞
 

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That was an impressive launch although the auto-subtitles made a real dogs dinner of translating the French launch director's commentary.
 
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There was problem with Hubble initally due to a fleck of paint de-focussing the optics and blurring the images- they worked out the error and subsequently replaced a section of the telescope via the space shuttle to correct it. Unfortunately the JAMES WEB "scope is not in near-earth orbit- so it has to work faultlessly from the off---posssibly against any normal terrestrial odds. :oops:
 

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There was problem with Hubble initally due to a fleck of paint de-focussing the optics and blurring the images- they worked out the error and subsequently replaced a section of the telescope via the space shuttle to correct it. Unfortunately the JAMES WEB "scope is not in near-earth orbit- so it has to work faultlessly from the off---posssibly against any normal terrestrial odds. :oops:

Dryce in pedant mode: The initial problem with Hubble was that the main mirror was incorrectly ground.

Which was corrected partially by software and then by an additional corrective optical package being installed.

And yes - to do that sort of correction with the James Webb telescope would be difficult. Hubble was put in orbit by basically lifting it in a space shuttle and then abandoning it in orbit before the shuttle returned to Earth - which meant that it was possible to revisit it using the shuttle to update it. Sending astronauts to visit and fix the James Webb telescope would be substantially more difficult and more dangerous (and even more expensive).
 

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What's next is a long period of cooling down and then calibration. In absolute vacuum all sorts of materials will gas off so they are deliberately cooling the instruments very slowly to minimise anything that gases off from condensing on the optical surfaces and degrading performance. Some heating is involved to control this process. The MIRI instrument which needs to be the coolest will take 3 months to cool, then there is a refrigeration plant to keep it cool. There is even some petrol head content. As an owner of a boxer engine I was pleased to discover that the refrigeration compressor uses horizontally opposed pistons for perfect primary balance to keep vibration from impacting on the sensitive instruments.

Why will it take six months to see JWST's first science images?
 

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