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2022-01-09, 15:05   #78
chalsall
If I May

"Chris Halsall"
Sep 2002

243448 Posts

Quote:
 Originally Posted by retina Pointing the mirror directly to the Sun would make for a nice temporary light show. A 10B firework. Thanks for the idea. Only you... 2022-01-09, 15:32 #79 Dr Sardonicus Feb 2017 Nowhere 169E16 Posts Quote:  Originally Posted by retina Yes, but it is more than that. Test equipment doesn't align or calibrate itself. The root problem was with procedures that were not followed to ensure such a basic error never occurred. I did mention that the report identified how the error happened, and provided a link for anyone interested in the details. Quote:  Originally Posted by retina Pointing the mirror directly to the Sun would make for a nice temporary light show. A10B firework. Thanks for the idea.
Alternatively, it might be possible to reorient the thing so the sun shield "flashes" the Earth. It's fairly reflective, and a lot bigger than the mirror.

2022-01-09, 16:13   #80
Uncwilly
6809 > 6502

"""""""""""""""""""
Aug 2003
101×103 Posts

101001001010112 Posts

Quote:
 Originally Posted by Dr Sardonicus Alternatively, it might be possible to reorient the thing so the sun shield "flashes" the Earth. It's fairly reflective, and a lot bigger than the mirror.
It would still be subpixel size for any detector working in the visible and would be too faint for the Mark I eyeball.

2022-01-09, 16:41   #81
Dr Sardonicus

Feb 2017
Nowhere

2·3·5·193 Posts

Quote:
Originally Posted by Uncwilly
Quote:
 Originally Posted by Dr Sardonicus Alternatively, it might be possible to reorient the thing so the sun shield "flashes" the Earth. It's fairly reflective, and a lot bigger than the mirror.
It would still be subpixel size for any detector working in the visible and would be too faint for the Mark I eyeball.
Come to think of it, the sun shield will be reflecting sunlight at us, or nearly at us, all the time anyhow.

Oh, no! This means the James Webb Space Telescope will increase Global Warming!

;-)

Last fiddled with by Dr Sardonicus on 2022-01-09 at 16:41 Reason: fignix posty

2022-01-09, 19:20   #83
xilman
Bamboozled!

"𒉺𒌌𒇷𒆷𒀭"
May 2003
Down not across

23·5·283 Posts

Quote:
 Originally Posted by Uncwilly It would still be subpixel size for any detector working in the visible and would be too faint for the Mark I eyeball.
That is an interesting claim. I have no reason to doubt you but I will "trust but verify" regardless.

Given that Gaia, which is much smaller and less reflective than JWST, is visible from L2 with my kit, I look forward to imaging JWST when the observatory is working again. Gaia is ~mag 20-22 which takes 30-180 minutes for a decent SNR; JWST should be 16-18, or 40 times brighter. Ten magnitudes way too faint for naked-eye detection (a factor of 10,000) in general but a specular reflection from the entire sun shield is not "in general".

 2022-01-09, 20:41 #84 firejuggler     "Vincent" Apr 2010 Over the rainbow 2,843 Posts Lego has a JWST st apparently or someone claim.. anyway https://twitter.com/LEGO_JWST/status...87469361479681
 2022-01-24, 19:41 #85 firejuggler     "Vincent" Apr 2010 Over the rainbow 2,843 Posts JWST arrived home https://blogs.nasa.gov/webb/2022/01/...arrives-at-l2/
2022-01-24, 22:29   #86
Dr Sardonicus

Feb 2017
Nowhere

2·3·5·193 Posts

Quote:
 Originally Posted by firejuggler JWST arrived home https://blogs.nasa.gov/webb/2022/01/...arrives-at-l2/
And quite a "Welcome home!" it will be, too. The housewarming cooling party is going to last for several weeks!

2022-01-25, 16:23   #87
tServo

"Marv"
May 2009
near the Tannhäuser Gate

5·157 Posts

Quote:
 Originally Posted by Dr Sardonicus And quite a "Welcome home!" it will be, too. The housewarming cooling party is going to last for several weeks!

Cold, indeed. Its final operating temp on the cold side will be about 40 degrees Kelvin !!!
It's around 62 K now.
Since heat is light, the colder it is the less interfering light there is.

2022-01-26, 01:18   #88
kriesel

"TF79LL86GIMPS96gpu17"
Mar 2017
US midwest

73×89 Posts

Quote:
 Originally Posted by tServo Since heat is light
Radiated heat is photons; convected heat is enthalpy of moving matter; conducted heat is phonons and electrons and maybe more. Space near L2 is not quite a perfect vacuum, even without the discharge of stationkeeping thrusters of JWST. The energy conveyed by solar wind to L2 orbit is probably usually very low density, but not zero.
http://www.dept.aoe.vt.edu/~cdhall/c...nvironment.pdf

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