Amazing James Webb Space Telescope

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Troels
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Re: Amazing James Webb Space Telescope

Post by Troels »

Fascinating technology.
I read somewhere, that they actually had to heat the electronics during the first part of the travel to prevent humidity condensation.
After released in empty space the unfolded sunshields will protect the equipment from further temperature shifts and the final cool down can begin.

I have seen reports that all mirror adjustments are working perfectly and ready for the complicated fine adjustments!
Troels Holm, biologist (retired), environmentalist, amateur photographer.
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rjlittlefield
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Re: Amazing James Webb Space Telescope

Post by rjlittlefield »

Sounds like a good answer here:

https://nasa.tumblr.com/post/1761994558 ... webb-space
In the first month: Deployment of the secondary mirror and the primary mirror occur. As the telescope cools in the shade of the sunshield, we turn on the warm electronics and initialize the flight software. As the telescope cools to near its operating temperature, parts of it are warmed with electronic heaters. This prevents condensation as residual water trapped within some of the materials making up the observatory escapes into space.
--Rik

rjlittlefield
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Re: Amazing James Webb Space Telescope

Post by rjlittlefield »

"Fine phasing" is now complete -- the James Web Space Telescope has been adjusted to give diffraction limited focus!

There's a good video overview of the process.

https://www.nasa.gov/press-release/nasa ... ccessfully

--Rik

rjlittlefield
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Re: Amazing James Webb Space Telescope

Post by rjlittlefield »

Today the Algorithm offered me this video:
https://www.youtube.com/watch?v=Pu97IiO_yDI ("Why Are there Holes in the James Webb Sunshield? ... Smarter Every Day 270")

Selected highlights:
1. The holes are to let the air out, so the heat shield did not blow up like a balloon during launch.
2. The surface shape of each layer of the shield was carefully measured and controlled to an accuracy of about 0.005 inch.
3. That accuracy is required because the layers of the shield actually comprise a sort of IR light pipe that is shaped to efficiently direct heat to the edge of the shield so it can escape to open space. The model in my own head now is that each spot on the shield can "see" open space via a sequence of reflections between layers. I assume the designers wanted the number of reflections to be as small as possible, hence the carefully controlled shapes.
4. The fellow who converted from the surface shape measured in 1 G, to the surface shape expected in 0 G, was a PhD in nuclear fusion, who grew up in a small town in India where there was no television, no telephone. What a life arc! (51:10-51:50).

--Rik

ModelZ
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Re: Amazing James Webb Space Telescope

Post by ModelZ »

Really nice video, thanks. Good family work!
The bit on layers shaped to channel out the radiation was indeed striking. Never thought of that.
I was hoping that they'd say something about what is happening when a micrometeorite (inevitably) hits the shield. How many layers is it likely to penetrate before it evaporates? A big enough would go through all the way - I wonder how critical a heat leak would that kind of straight tunnel cause?

Btw. just recently talked with someone who worked hands on the GAIA satellite project. This was lauched 2013, also from Kourou (and ended up in the same Lagrange L2). Since then they had to heat up (to room temperature) the satellite twice to try to get rid of the condensed water inside the satellite box. If they have to do the same with JWST that surely means significant off-line time because of the low op temps required.

-Karl

ChrisR
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Re: Amazing James Webb Space Telescope

Post by ChrisR »

Interesting comments on "that" image:
https://www.livescience.com/james-webb- ... -explained
Chris R

MarkSturtevant
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Re: Amazing James Webb Space Telescope

Post by MarkSturtevant »

Happy to drop in on the party again. It's all been just so amazing! Here is one web site that has been posting the latest released images, with explanations: https://webbtelescope.org/news/first-images/gallery.
I haven't found new ones lately, but I expect it needs to get to work and not just be used to produce eye candy.
Mark Sturtevant
Dept. of Still Waters

viktor j nilsson
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Re: Amazing James Webb Space Telescope

Post by viktor j nilsson »

If you've missed it, here's a site that lets you compare images from the Webb telescope to images of the same objects taken with Hubble:

https://www.webbcompare.com/

Spoiler: it's amazing. Makes Hubble look like a dropped Mitutoyo.

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