NASA said today that one of the Webb Space Telescope's primary mirror segments was hit by a micrometeoroid, a small asteroid fragment, between May 23 and May 25. Initial assessments of the telescope found that the spacecraft was still performing exceptionally well, though the effects of the impact were noticeable in recent data readouts.
Micrometeoroids are extremely small (dust-sized), fast-moving space debris. They're a regular part of a hostile space environment that will bombard the Webb telescope throughout its years in operation.
"With Webb's mirrors exposed to space, we expected that occasional micrometeoroid impacts would gracefully degrade telescope performance over time," said Lee Feinberg, Webb optical telescope element manager at NASA, in an agency release. "Since launch, we have had four smaller measurable micrometeoroid strikes that were consistent with expectations and this one more recently that is larger than our degradation predictions assumed."
[...] Thankfully, Paul Geithner, a technical deputy project manager at NASA, said in the release that "We designed and built Webb with performance margin – optical, thermal, electrical, mechanical – to ensure it can perform its ambitious science mission even after many years in space."
See also: Webb: Engineered to Endure Micrometeoroid Impacts
(Score: 2) by Runaway1956 on Thursday June 09 2022, @07:42PM
"No, James, you don't need a BB gun for your birthday. You'll just put your mirrors out!"
“I have become friends with many school shooters” - Tampon Tim Walz
(Score: -1, Spam) by Anonymous Coward on Thursday June 09 2022, @09:05PM
UP MY FILTHY ASS!
I WANT MY RECTUM TO CLAMP DOWN UPON IT AS I CUM
I WANT MY SEMEN TO SHOOT OUT LIKE A BOOMERANG
I WANT MY TOES TO CURL AS I EJACULATE
FUCK ME
(Score: -1, Spam) by Anonymous Coward on Thursday June 09 2022, @09:08PM
I firmly clutch my scrotum as I ejaculate one month's worth of sweet semen into the mouth of my bear skin rug.
(Score: 2) by PiMuNu on Thursday June 09 2022, @11:11PM (9 children)
> this one more recently that is larger than our degradation predictions assumed.
Maybe JWST was just unlucky. How well is the JWST space environment known? Anyone know how much larger than predictions?
It's a stats question. What is the probability that this was bad luck.
(Score: 2) by JoeMerchant on Friday June 10 2022, @12:58AM (8 children)
I had a concern about location in a Lagrange point, which is naturally dusty, but that should be relatively slow moving dust.
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(Score: 2) by PiMuNu on Friday June 10 2022, @03:12AM
Not much they can do about it now!
(Score: 2) by Immerman on Friday June 10 2022, @01:54PM (6 children)
Are they really though?
I mean, I know the the L4 and L5 points are quasi-stable and tend to accumulate clouds of dust and asteroids. But the L1,2,and 3 points are all highly unstable energetic saddle-points where you mostly need complex 3D orbits with active station-keeping to remain there.
I suppose they still act as energetic "doorways" or "lenses" that focus stuff passing nearby, don't they? So the density is probably at least a fair bit higher than anywhere else near Earth's orbit.
(Score: 2) by JoeMerchant on Friday June 10 2022, @02:18PM (3 children)
Yeah, L4 or 5 would have been a clearly bad choice, but L2 still feels like a compromise compared with a simpler extra-lunar orbit. Maybe L2 is shielding from more catastrophic failure hazards than being "out on it's own", but it does seem like a good place to collect rocks, even if they are just passing through. I'm sure people with far more knowledge have "run the numbers" long ago to come to this decision, shame they feel it's too much techie detail to share with the common folk.
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(Score: 2) by Immerman on Saturday June 11 2022, @01:29AM (2 children)
I don't think it's a compromise - L2 is pretty much the *only* place they could put it.
It's an IR telescope, so cold is key. It's already been mentioned that its orbit keeps its sun-shade in constant sunlight for thermal stability - any change in temperature is going to subtly change the dimensions of the entire telescope, and throw off the alignment of those incredibly precisely tuned mirrors.
And the most important part of that is to NEVER have anything stronger than starlight shine on its dark side - it's designed to operate only a few dozen degrees above absolute zero, it doesn't take much to start warming things at that temperature.
*Any* orbit around Earth would have the dark side of Webb facing the sunny side of Earth for half its orbit - and Earth reflects a LOT of sunlight, as well as emitting a LOT of thermal IR. Far too much to keep the telescope cold and stable.
The only other option is a solar orbit outside Earth's - but that would mean much higher energy consumption for communication, and probably no really high-speed communication since almost its entire life would be spent several AU away from Earth as it slowly fell further and further behind, passed behind the sun, and slowly gets overtaken by Earth again..
(Score: 2) by JoeMerchant on Sunday June 12 2022, @12:01AM (1 child)
Any orbit other than polar, which a clever missile man could precess once a year so it stays on the day-night line all the time.
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(Score: 2) by Immerman on Sunday June 12 2022, @02:37AM
The orbit would still be in a plane that cuts through the center of the Earth, so even with the Webb's heat shield pointed straight at the sun, the dark side of Earth would still be shining on the cold side of Webb - probably still far too much heat.
Though it doesn't seem as though the telescope is articulated relative to the heat shield, instead the whole thing tilts relative to the sun and spins on its axis to look in different directions. So it could potentially tilt its axis enough to keep the Earth behind the shade as well - at least if it's far enough away - but that would radically reduce the potential field of view at any time.
But there's no way to keep the shield blocking out the moon since it travels so much further from the sun than Webb or Earth. And so for half of every month the bright side of the moon would be shining on Webb's dark side.
(Score: 2) by JoeMerchant on Friday June 10 2022, @02:21PM (1 child)
Ah, so, I finally dug deep enough to find a graphic that made some sense, L2 gets earth shielding from solar radiation. All the other press I've seen to-date make a big kerfuffle about the Webb's own multi-layer shield that it unfolds, but never really mentioned that L2 is a naturally shielded point as well.
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(Score: 0) by Anonymous Coward on Friday June 10 2022, @04:23PM
The L2 point is in the Earth's shadow, but not the orbit about L2. For thermal stability reasons (and solar power reasons), Webb is designed to be in the sunshine all of the time, even clear of the shadow from the Moon, so that's why the sun shade is so important (Hubble goes in/out of shadow and you have to let the telescope settle down and the thermal gradient dissipates. In fact, the minimum distance between Webb and the L2 point is 250,000 km [stsci.edu].
(Score: 2) by krishnoid on Thursday June 09 2022, @11:15PM
Good thing they learned from other failures [youtu.be] involving micrometeoroids.
(Score: 0) by Anonymous Coward on Friday June 10 2022, @01:02PM (2 children)
we are getting pelted with road chum.
Statistically, this looks to be a case of underestimating the importance of protecting the instrument.
Chaulk it up to experience.
Every moment here on, the telescope is degrading faster than predicted.
Pray nothing bigger than a microthing comes along.
(Score: 0) by Anonymous Coward on Friday June 10 2022, @01:22PM (1 child)
Why do you say that? One event is not much to make a statistical argument as to whether the particle distribution assumed before launch is good or not.
(Score: 0) by Anonymous Coward on Friday June 10 2022, @10:55PM
It is probably a lot dustier than we realise out there.
Consider we are in a gravity well, pulling stuff towards us in a constant shower either internally from our accretion disk or from the Ort cloud.
The Sol system is moving in and out of the accretion disk of the Milky Way.
The Milky Way has stuff raining in on it from the Local Group.
Beyond that, the effects of Expansion start to stir up our Baryonic Matter.
Although empty, if you include virtual particles popping in and out of existence, it is a busy place.
(Score: 2) by JoeMerchant on Monday June 13 2022, @12:38PM
>so for half of every month the bright side of the moon would be shining on Webb's dark side.
Which is different from lunar L2 how?
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