James Webb, Halley's Comet might be set for cosmic dust-up
- Reference: 1658846708
- News link: https://www.theregister.co.uk/2022/07/26/james_webb_and_halleys_comet/
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JWST's mirror is exposed to the vacuum of space, and while that means it produces [1]images with far more clarity than Hubble, it also has nothing to shield it from sand grain-sized debris traveling at 10km/second, or 6.2 miles/second (over 22,300mph).
Small debris can cause serious damage, such as the May impact on Webb's mirror that caused [2]irreparable harm , but which NASA was able to correct for.
[3]
Halley's Comet itself won't be back in the inner solar system [4]until 2061 , but the bright tail trailing out behind it is filled with dust, debris and ice shed by the comet. It's that debris field that JWST is predicted to enter in 2023 and 2024.
Webb wasn't built to last
According to [5]Nature , meteor shower dust like that left behind by Halley only constitutes around 5 percent of the impact risk to Webb, while the rest is from random hits from stray dust. Scientists have long planned for such hits during Webb's lifetime, but May's unexpected impact has had scientists re-evaluating the potential for serious damage and developing custom meteor shower forecasts at Lagrange point 2, where Webb sits in space.
[6]A moment of tension as the James Webb Space Telescope stretches sunshield on way to L2 destination
[7]Hubble space 'scope brings its Cosmic Origins Spectrograph back online
[8]Don't give up on Planet Nine yet: Hubble 'scope finds just such a world a mere 336 light-years away
[9]Behind time and way over budget, but the James Webb Space Telescope has finally been put together
With those forecasts, the space telescope's operators can reposition the telescope to avoid incoming dust, but such forecasts still leave Webb exposed to unpredictable hits from single micrometeoroids, as was the case in May.
Hubble, by contrast, which sits in low earth orbit and is encased within a tube, is still operating after more than 30 years.
[10]
Webb gets around Hubble's primary limitation of having a limited observational wavelength in a couple of ways: It doesn't lock its mirror in a tube, and it sits far enough from the Sun that it can offset heating that limits wavelengths. While those elements make Webb a better observer of the cosmic condition, it also means it's unserviceable once deployed and is exposed to lots of potential damage.
NASA said the [11]minimum baseline for JWST's mission duration is five years, with the agency hoping to get a decade out of the telescope. The fuel in JWST is enough to keep it in position and transmitting data for longer than a decade, NASA said, but that's if a grain of sand doesn't turn Webb into a [12]$10 billion lesson in protecting sensitive equipment. ®
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[1] https://www.theregister.com/2022/07/12/jwst_first_image/
[2] https://www.theregister.com/2022/06/09/james_webb_meteoroid/
[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=2YuAPncgue-GxOvx4FBheBQAAAEs&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[4] https://www.space.com/19878-halleys-comet.html#:~:text=Halley's%20Comet%20is%20arguably%20the,projected%20to%20return%20in%202061.
[5] https://www.nature.com/articles/d41586-022-01877-8
[6] https://www.theregister.com/2022/01/04/jwst_sunshield/
[7] https://www.theregister.com/2021/11/30/hubble_cosmic_origins_spectrograph_back_online/
[8] https://www.theregister.com/2020/12/11/planet_nine_hubble/
[9] https://www.theregister.com/2019/08/29/james_webb_space_telescope/
[10] 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=44YuAPncgue-GxOvx4FBheBQAAAEs&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[11] https://blogs.nasa.gov/webb/2021/12/29/nasa-says-webbs-excess-fuel-likely-to-extend-its-lifetime-expectations/
[12] https://www.theregister.com/2022/07/16/ames_webb_space_telescope/
[13] https://whitepapers.theregister.com/
"it sits far enough from the Sun that it can offset heating that limits wavelengths"
It only sits about 1 million miles further out from the Sun than the Earth, which itself about 93 million miles away from the Sun. So the heating difference based on distance from the Sun alone is about 2%.
The no tube is mostly a function of mass. A tube for a 6m mirror is going to be massive
It's fairly easy to get a telescope tube in space to radiate down to a pretty cold temperature - enough that it has no background at JWSTwavelengths
The distant orbit is mostly so that the Earth doesn't fill the sky and limit your range of observations, it also reduces the heat load from the Earth
even on thin ice your best ice skates will not help you.
there are dangers in the world .... in space there are no safe zones.
the cutting edge of discovery is not with out risk bit the risk is worth taking.
If only there was some way we could have known?
Oh wait.
"I don't like sand. It's coarse and rough and irritating and it gets everywhere."
Forcefields
This is why I sent an email to NASA, specifically advising them to fit it with a forcefield, like the one recovered from Roswell. I knew this would happen.
I didn't get a reply, but I figured that would be the case, given my security clearance.
The mote in JWSTs eye
> that's if a grain of sand doesn't turn Webb into a $10 billion lesson in protecting sensitive equipment.
Presumably back in 1993 when this telescope was being planned the powers that be assumed it would have been launched, done all its science and gone
Still, if they start planning a replacement now, it should be ready by 2050.
"Webb gets around Hubble's primary limitation of having a limited observational wavelength [by] It doesn't lock its mirror in a tube"
I'd have thought that it was more a case of being a big lump to get into space as it is without the added complication of a tube. Even more significantly the tube itself would have to be protected from solar heating, otherwise its IR radiation would dazzle the instruments.