Meteoroid hits main mirror on James Webb Space Telescope
- Reference: 1654786806
- News link: https://www.theregister.co.uk/2022/06/09/james_webb_meteoroid/
- Source link:
The NASA-built space observatory reached its final destination, the L2 orbit, a million miles away from Earth, at the [1]end of January .
In a statement, NASA [2]said the impact happened some time at the end of May. Despite the impact being larger than any that NASA modeled and "beyond what the team could have tested on the ground," the space agency said the telescope continues to perform at higher-than-expected levels. The telescope has been hit on four previous occasions since launch.
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James Webb's primary mirrors make up the gold-colored array that occupies a good portion of the telescope's body. Those 18 gold-plated mirrors are carefully aligned at the [4]nanometer scale to reflect infrared light to James Webb's cameras, a process that took [5]months for scientists to complete from ground control.
[6]
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The C3 mirror, which took the hit, will have to be adjusted to counter the distortion and noise that resulted from the impact.
"Engineers have already performed a first such adjustment for the recently affected segment C3, and additional planned mirror adjustments will continue to fine tune this correction," NASA said. Micrometeoroid impacts like this one are "considered an unavoidable chance event," the agency said.
[8]
Micrometeoroids are small – often less than one millimeter – but they move so fast relative to spacecraft orbiting Earth that they can cause craters [9]visible to the naked eye . Space debris of that size has a typical impact velocity of 10km/s (22,369mph), while meteoroids, typically considered to be larger than a grain of rice, hit at double the velocity.
[10]AI to help study first images from James Webb Space Telescope
[11]NASA awaits approval of $24bn 2022 budget
[12]Photon fantastic: James Webb Space Telescope spies its first starlight
[13]Second Trojan asteroid confirmed to be leading our planet around the Sun
Spacecraft like James Webb are designed to withstand these types of impacts, but there are limits to what can be done to minimize them above a certain scale, especially when dealing with rocks traveling 6-12 miles a second. Herein likes the bright spot for NASA scientists, who are accustomed to dealing with mission-altering problems.
"As a result of this impact, a specialized team of engineers has been formed to look at ways to mitigate the effects of further micrometeoroid hits of this scale," NASA said.
Along with protecting James Webb, NASA wants to use the telescope to better understand the dust and micrometeoroids whipping around the solar system, particularly at the L2 point where the telescope sits. L2 is considered a "sweet spot" for galactic observation, and other space agencies have [14]plans to deploy missions to the same area.
To those worried that this impact will delay or hinder Webb's work – and those hotly anticipating the first images scheduled for release in July – NASA said it's still on schedule. ®
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[1] https://www.theregister.com/2022/01/25/james_webb_space_telescope/
[2] https://blogs.nasa.gov/webb/2022/06/08/webb-engineered-to-endure-micrometeoroid-impacts/
[3] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=2&c=2YqIZIN5rNPW9yosgOqr@PwAAAAM&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://www.theregister.com/2022/01/25/james_webb_space_telescope/
[5] https://www.nasa.gov/press-release/nasa-s-webb-reaches-alignment-milestone-optics-working-successfully
[6] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44YqIZIN5rNPW9yosgOqr@PwAAAAM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[7] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=3&c=33YqIZIN5rNPW9yosgOqr@PwAAAAM&t=ct%3Dns%26unitnum%3D3%26raptor%3Deagle%26pos%3Dmid%26test%3D0
[8] https://pubads.g.doubleclick.net/gampad/jump?co=1&iu=/6978/reg_offbeat/science&sz=300x50%7C300x100%7C300x250%7C300x251%7C300x252%7C300x600%7C300x601&tile=4&c=44YqIZIN5rNPW9yosgOqr@PwAAAAM&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[9] https://www.esa.int/esapub/bulletin/bullet80/ace80.htm
[10] https://www.theregister.com/2022/06/09/ai_jwst_morpheus/
[11] https://www.theregister.com/2022/03/10/nasa_2022_buget/
[12] https://www.theregister.com/2022/02/05/jwst_photon/
[13] https://www.theregister.com/2022/02/02/second_earth_trojan_asteroid_confirmed/
[14] https://www.esa.int/Science_Exploration/Space_Science/Herschel/L2_the_second_Lagrangian_Point
[15] https://whitepapers.theregister.com/
Re: Mitigation Options?
>1. Is there enough strength in the mirror & coating to avoid damage?
For a rock doing 10km/s, roughly the speed of an explosive shaped charge, like the ones you use to make holes in tanks? No
>2. If there is an impact & damage occurs, how much can you sustain before the capabilities are degraded?
If you just punch a hole through a solar panel or sunshield - minor effect.
Even a ding out of a mirror isn't a huge problem. The mirrors are very stiff so you tend to make a small chip rather than bending it.
>3. How much adjustment do you have to correct mirror alignment if an impact duffs up more than specs on the coating?
You can't realign to fix a chip smaller than a mirror segment. Potentially you could lose an entire segment if a rock totally smashed it, or hit it hard enough to bend the support. Still better than losing an entire mirror
Disappointing
Am I only person to feel a little disappointed by this? They say they knew it was a risk and tried to mitigate by material choice, but given it will have some impact to the mission before we've even taken a picture it would suggest a type of shield or alternative protection really was a requirement. Pleased they can minimise the impact, but given how early we are in the planned mission it's not looking super promising we'll will get close to 10 years planned, let alone a possible extension.
Re: Disappointing
Apparently, it's been hit five times (including this one) since it went up, but this is the first one on the mirror I believe (not 100% certain about that bit).
[1]I saw it on the BBC write up .
[1] https://www.bbc.co.uk/news/science-environment-61744257
Re: Disappointing
Any shield takes mass, and runs the risk of the shield material being kicked towards the telescope...
Any mass you spend on shield is less station keeping fuel *AND* more fuel required for each operation, compounding the reduction to lifespan.
Re: Disappointing
It's a matter of trade offs. If you put shielding up, you reduce the lift to your sensors, meaning you need a bigger mirror to get the same resolution, meaning a bigger shield, Mass goes up, costs go up and pretty quickly that's your mission cancelled.
They would have done the maths, calculated the odds of getting hit by debris, based on all of the current experience with things in similar orbits and built in some margin.
Yes there will be a very large number of people cursing right now, rechecking calculations, and all that stuff. But Quite frankly, if you're going to push the boundaries of science you have to take some chances.
Re: Disappointing
Given the speed and energies they're talking about, I really doubt that a shield would have been particularly effective. I'm sure that this was less of an impact, and more of a through-and-through, with the meteoroid passing straight through the mirror.
I'm wondering whether the L2 point will actually be busier than open space. After all, if it's a point of gravitational neutrality, then will debris have gathered since the formation of the Earth and Moon.
If there is more debris, maybe the life of this telescope will be short.
Re: Disappointing
>I'm wondering whether the L2 point will actually be busier than open space
It's not a stable minima so it doesn't collect debris.
It's a lot better than low earth orbit like Hubble, there sin't a lot of space debris 1.5M km away
Possibly there is a higher risk being outside the moon's orbit but it's likely this bit was just a random smaller version of your average dinosaur destroyer.
They must have been Touched By His Noodly Appendage.
This whole project's endgame is to create a gigantic pasta-strainer in space, isn't it?
Mitigation Options?
Given where it is and the likelihood of this recurring in the lifetime of the platform the options are rather limited.
1. Is there enough strength in the mirror & coating to avoid damage?
2. If there is an impact & damage occurs, how much can you sustain before the capabilities are degraded?
3. How much adjustment do you have to correct mirror alignment if an impact duffs up more than specs on the coating?
One assumes that this was all calculated into the design but being rather pessimistic and the huge cost over runs on the project, one wonders.......
It will be really sad and somewhat ironic if JWST is outlived by Hubble. There is a planned life of 10 years with an expected life of 20, I just hope that continued exposure to events like this does not screw that up. Bluntly, if it is anything to do with hardware that cannot be corrected by software or post image processing then it is stuffed.