back to article James Webb, Halley's Comet may be set for cosmic dust-up

The James Webb Space Telescope is predicted to pass through Halley's Comet's debris trail next year, meaning that particles could further endanger its sensitive primary mirror. JWST's mirror is exposed to the vacuum of space, and while that means it produces images with far more clarity than Hubble, it also has nothing to …

  1. Doctor Syntax Silver badge

    "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.

    1. Crypto Monad Silver badge

      "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%.

      1. Yet Another Anonymous coward Silver badge

        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

        1. Yet Another Anonymous coward Silver badge

          Worth noting, Hubble's full tube was to control stray light from the big bright Earth just next door.

          1. Anonymous Coward
            Anonymous Coward

            Blackbody emmisions source as well right?

            Any structure that is close enough and big enough to protect the mirrors would also be a source of further black body infrared emissions and need to be cooled to low Kelvins to prevent interference right?

        2. Doctor Syntax Silver badge

          "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"

          Only if you shelter it from the sun. That would very likely require a larger shield, requiring larger supports, more mechanish to fold out. Both tube and larger suhshield means more volume. More volume means a bigger nose cone. Still more mass. More fuel to get them into orbit. More mass yet.

          1. Yet Another Anonymous coward Silver badge

            Nope you can simply wrap it in layers of reflective foil. You get a vacuum between them for free, think of a Russian doll of 100 thermos flasks.

            I saw one proposal for a passively cooled IR telescope that reckoned it could get down to 40K with just shields

            JWST sheild is big to keep the whole mirror in shadow of the Sun and Earth

            1. Yet Another Anonymous coward Silver badge

              Sorry that was a bit short and rude.

              The large self supporting steered shield on JWST is a big bit of engineering. But a thermal shield around a tube is just wrapping it with 20+ layers of Aluminium coated mylar each 0.05mm thick. Like a super lightweight version of the silver blankets at the end of marathon.

              Roughly each layer halves the heat load, so 10-20 layers in space is awesome insulation

  2. boris9k3

    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.

  3. Steve Button Silver badge

    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."

  4. This post has been deleted by its author

  5. Kaltern


    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.

    1. This post has been deleted by its author

    2. Yet Another Anonymous coward Silver badge

      Re: Forcefields

      Unfortunately Bigfoot stole the plans during the break-in by mothman

  6. Pete 2 Silver badge

    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 <phut!> before Halley's dust cloud became bothersome. But with all the delays, that kinda didn't happen.

    Still, if they start planning a replacement now, it should be ready by 2050.

    1. Anonymous Coward
      Anonymous Coward

      Re: The mote in JWSTs eye

      Wr get meteor showers from Halley's dust every year. Right now the comet isn't close, it'll be back in 2061.

      1. Yet Another Anonymous coward Silver badge

        Re: The mote in JWSTs eye

        Unless the comet is assigned to the SLS project, then its return will be delayed to 2090

      2. Paul Hovnanian Silver badge

        Re: The mote in JWSTs eye

        Halley's comet (and others) leave a trail of particles along their comets' orbits. We know where these trails are and in which direction most of the bits are traveling. Perhaps it's just a matter of pausing observations and turning the JWST mirror edge-on to the trajectories as it crosses them.

        1. Mad Ludwig

          Re: The mote in JWSTs eye

          Unfortunately, probably not - my understanding is that if the cold parts of the instrument are ever exposed to the sun, the thermal stress of the sudden heating would destroy them, so the telescope is very limited in what orientations it can be at.

    2. Someone Else Silver badge

      Re: The mote in JWSTs eye

      You know - a starship circlin' in the sky - it ought to be ready by 1990

      They'll be buildin' it up in the air ever since 1980

      Hijack by (the original) Jefferson Starship

      That sucker is waaayy behind schedule!

  7. nagyeger

    Rule of thumb: 1 astronaut-year spacewalk = 1 dead astronaut

    Just be glad the telescope's not in LEO. You get gravitation pulling more natural particles in towards you and space debris too.

    IIRC, the impact hazard from space debris starts getting noticeably higher than natural particles at around 0.1mm size (estimated size you can protect an astronaut against), but common knowledge back when I was in the lab was that you'd get about 1 astronaut-killer impact per astronaut-year of space-walk, so with JWST being 25m2, I'm not surprised it's got a few noticeable craters. (as well as hundreds of less-noticeable ones).

    As for protecting the mirror.... that's a tough one. If it were my mirror and you gave me the choice of 'protecting' it with 1mm of Aluminium/plastic/whatever or exposing it directly to 0.1-3 mm particles at 66km/s (Orionid meteor shower), then I'd almost certainly choose to not have the inadequate 'shield', and just hold the mirror edge-on to the stream, so as many of them miss as possible.

    Each impact on any shield is going to make a shower of ejecta (inside and outside, if the shield isn't thick enough), as the particle blows itself and the target to plasma and makes a pretty crater. Impact ejecta like that can cause a massive amount of damage to surrounding surfaces, far more than the initial impactor would.

    To properly protect it, you either need a few tens of km of atmosphere or multiple layers of stuff to break it up, spread it out, break up and slow down the high-speed ejecta, spread that out, etc. How big was that telescope again?

    (Fun viewing:, but remember children, this is lab simulation of some slow orbital collisions, certainly not head-on, and let alone the impact speed of any natural meteor streams.)

  8. Paul Cooper


    "Unserviceable" means not functioning! I'm sure that the article really means "not serviceable".

    1. Yet Another Anonymous coward Silver badge

      Re: Unserviceable????

      No user serviceable parts inside ?

      1. ChrisC Silver badge

        Re: Unserviceable????

        Though at least the batteries WERE included...

    2. Yet Another Anonymous coward Silver badge

      Re: Unserviceable????

      Coincidentally just writing a safety course on how to label/explain things without causing dangerous "inflammable == not flammable" confusion.

      There was a plane crash that killed 100 people because expired != expended with oxygen generators

      1. Crypto Monad Silver badge

        Re: Unserviceable????

        Thank you for that, it led to some interesting reads:

        Wikipedia says simplistically that the canisters were expired but labelled "empty". The second goes into much more detail:

        According to ValuJet work card No. 0069, which was supplied to investigators, the second step of the seven-step removal process was If generator has not been expended, install shipping cap on firing pin.

        This required a gang of hard-pressed mechanics to draw a verbal distinction between canisters that were "expired," meaning most of the ones they were removing, and canisters that were not "expended," meaning many of the same ones, loaded and ready to fire, on which they were expected to put nonexistent caps. Also involved were canisters that were expired and expended, and others that were not expired but were expended. And then, of course, there was the set of new replacement canisters, which were both unexpended and unexpired.

    3. diodesign (Written by Reg staff) Silver badge

      Re: Unserviceable????

      Yeah, we mean not serviceable. Please don't forget to email if you spot anything wrong like this - we can't read every comment.


  9. DS999 Silver badge
    Thumb Up

    Given how well NASA has done with mission life extension

    Between Pioneer, Voyager, Hubble, the Mars landers and so forth, if they end up having one miss and JWST functions for less than the stated service life I'd be inclined to forgive them.

  10. Jan K.

    I don't understand the "it's unserviceable once deployed"? Is it a matter of distance from Earth?

    1. Mister Dubious

      Distance from Earth shouldn't raise servicing costs all that much, if NASA can be persuaded to skip the rockets and things and just hire an Uber.

      1. Dr. G. Freeman

        Shouldn't be too difficult to get there, it's not rocket science.

        1. The Oncoming Scorn Silver badge

          I Wish This Was A Joke.

          but a certain MSP partly named after mountain in Japan having won a certain contract for Tier 2 local support here in Canadaland, bid so low (So they could have both T1 & T2) wanted its support techs to travel to site by bus\c-train with parts & tools.

          One of my former colleagues was given $15K a year extra just to cover the Southern Alberta Area with his car* as there wasn't any public transport that would reach some of the Governmental offices & meeting SLA.. I keep getting recruiters on the phone telling me I would be ideal for a role & would I be interested, the rate is laughable & my response is usually along the line.

          This wouldn't be for Fu******* & GOA would it?

          Errr yes

          & the rate is still laughable I presume?

          Errr yes

          Please call me back when the rate is worthy of me.

          *That was it no further reimbursement

    2. Yet Another Anonymous coward Silver badge

      Yes its about 5x further away than the moon.

      Because of this it wasn't designed to be serviced, it's extremely fragile to save weight and none of the instruments are easily accessible, unlike Hubble

  11. Anonymous Coward

    Danger Will Robinson!

    The biggest danger to the Hubble is light and that is what the tube was designed to block.

    The biggest danger to the JWST is heat and that is what the heat shield was designed to block.

    The Hubble was designed to be serviceable and this design was needed as the initial Hubble configuration didn't work when it was deployed in space. The JWST was designed (just like planetary missions) to be unserviceable by other spacecraft but reprogrammable from ground control.

    And, FYI, the next Hubble sized telescope, the Nancy Grace Roman Space Telescope, is under construction and scheduled for launch in 2027. It is currently planned to orbit at L2. Longer term, the Large Infrared/Optical/Ultraviolet (IR/O/UV) Space Telescope is in the study stage with a planned launch in the early 2040s.

    I can't afford pints for the hundreds of boffins working on these projects so I'll drink one myself in their honor.

    1. The Oncoming Scorn Silver badge

      Re: Danger Will Robinson!

      Only one?


  12. ComputerSays_noAbsolutelyNo Silver badge

    More of them

    Now, that all the technical kinks have been worked out,

    couldn't they simply build more of them?

  13. Chris Coles

    Why not design and deliver a simple dust shield?

    All that is required is a dust shield, which should be easy to design, and deliver it to fly just beside JWST? Simple!

  14. Sgt_Oddball

    Having met...

    One of the space boffins using the JWST for his work last weekend (Bluedot festival - fun times) he was mentioning about it being a rare thing that luck plays a huge role in how long it lasted, but that saving the fuel will help massively since it means they can move it more to cope with damage.

    He also mentioned that he half expects it to be demolished by a passing Tesla... Not entirely sure if he was joking.

  15. This post has been deleted by its author

  16. Anonymous Coward
    Anonymous Coward

    Isn't L2 self-cleaning?

    I remember reading somewhere about Lagrange points being "self cleaning" i.e. although it doesn't take much fuel to stay there, nothing can stay there without spending that bit of fuel, because the orbital dynamics result in stuff drifting away from the point, which makes them good places to put spacecraft and not expect rocks to be hanging around to complicate your mission. So... that doesn't apply to comet dust? How do we get a refund?

    1. Anonymous Coward
      Anonymous Coward

      Re: Isn't L2 self-cleaning?

      I think an analogy is self-cleaning glass as used in office blocks: it's self-cleaning for airborne dust and dirt, but it's not bullet-proof - a bullet being equivalent to a fast moving spec of dust from Halley.

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