back to article James Webb Space Telescope runs one last dress rehearsal for its massive golden mirrors before heading to launchpad

ESA, CSA and NASA's James Webb Telescope opened its giant primary mirror one last time on Earth ahead of being packed up for long awaited launch later this year. The 6.5m structure, comprised of 18 hexagonal mirrors, was commanded from the Northrop Grumman testing control room in California to expand and lock itself into place …

  1. Eclectic Man Silver badge

    What amazes me is that a structure that can survive the extreme forces of lift off in a rocket, can then be assembled with such accuracy that it will be able to resolve images better than Hubble. Superb engineering.

    1. ITMA Bronze badge

      Are you talking before or after COSTAR and the various other fixes to address to monumental screwup of Perkin-Elmer?

    2. Yet Another Anonymous coward Silver badge

      The problem is that until it launches we won't know if it can unfold and align itself.

      1. ITMA Bronze badge

        Shudders at the thought of a repeat of the Galileo Jupiter mission...

    3. James Ashton

      The Hubble and the James Webb have about the same ability to resolve details. The James Webb is much larger, but it also uses much longer wavelengths of light (infra red) which cancels out that advantage as far as resolution is concerned. Obviously the James Webb is better than Hubble in many ways ... but resolving details is not one of them.

      Let's wait until it works before commenting on the engineering. There are just so many ways for it to fail. I can see SpaceX offering to run a repair or replenishment mission.

      1. Anonymous Coward
        Anonymous Coward

        The Moon orbits the Earth at an average distance of about 384,400 km (238,900 miles).

        The distance earth to the Earth-Sun L2 point, where the James Webb Space Telescope will be deployed, is roughly 400x the distance to the moon, at about 151.1 million km (For perspective Mars at its closest to Earth is about 62 million kilometers or ~38.6 million miles).

        It took just over 3 days for Apollo 11 to travel from earths orbit to orbit the moon.

        So with the above in mind I do not see SpaceX doing any repairs or replenishment missions.

        Hubble is in a low earth orbit at about 547 kilometers (340 miles) above Earth, about 300,000 times closer to earth than the James Webb Space Telescope when deployed.

        There were 5 services done in total, unless SpaceX is going to do service missions with autonomous machines, I just do not see them happening.

        STS-61 was a 11 day mission - 5 days working on Hubble.

        STS-82 was a 10 day mission - 5 days working on Hubble.

        STS-103 was an 8 day mission - 3 days working on Hubble.

        STS-109 was a 11 day mission - 5 days working on Hubble.

        STS-125 was a 13 day mission - 5 days working on Hubble.

        1. PerlyKing

          L2 is not 151.1 million km away

          You've slipped a couple of decimals, AC. Try 1.5 million km.

          It's still a long way beyond LEO, and your point more or less stands, but a little critical thinking should have suggested that 150 million km was a rather large distance in this context.

          1. Anonymous Coward
            Anonymous Coward

            Re: L2 is not 151.1 million km away

            I just grabbed the value from the wrong table

            But the point is still the same just 100x less, it is still too far for SpaceX to do maned service mission.

            1. Anonymous Coward
              Anonymous Coward

              Re: L2 is not 151.1 million km away

              Why the hell would we send Meatbags to do this?

              Would make more sense to send an unmanned satellite tender. Lighter, more efficient, an no need to even set it up for a return trip. And the trip out can be slower and efficient. That said, it all depends on what the failures that need to be addressed are.

              The big question would be is it cheaper to fix or to build a new one. Considering it's history of delays and cost overruns, repair may it it's only hope if there is a failure, as we probably won't get to build a new one for a while unless we get a few years of science out of it to showcase what we are missing.

              Hubble was the same way to some degree, that once it started operating at capacity, it was clear that it was worth the money pretty quick, that sold the public on the follow on projects like Spitzer and the JWST. Hopefully the launch goes off without a hitch and the thing holds together though. It would be nice to have the "Too big to fail" part of this in the rear-view for a while.

        2. Aladdin Sane

          L2 is about 1.5 million kilometers from Earth, not 151 million.

        3. Binraider Silver badge

          Dragon wouldn't be doing any servicing missions, if nothing else it hasn't the delta V to do it. But an appropriately configured Starship - or even SLS/Orion would be capable of doing so. It might be a better use for the latter in fact.

          There were various extended range options for the Orbiter considered like doubling up on the SRB's but they never made it off the page. Perhaps for the best.

        4. James Ashton

          SpaceX is planning to take hordes of people to Mars. If they can do that, making it to the Earth-Sun L2 point and back to refill the liquid helium is a short trip. I'm not thinking Falcon 9 here but Starship. ("Not the local bulk cruisers mind you, I'm talking about the big Corellian ships now.") Obviously NASA didn't consider anything like this capability would exist in the foreseeable future (especially given that James Webb was supposed to launch in 2007) but hopefully they're wrong and Starship works.

        5. Nonymous Crowd Nerd

          What you're describing here begins to look like a very "ambitious" project indeed. "Bold" even.

          I'm certain Sir Humphrey would have come up with an appropriate phrase...

          1. Binraider Silver badge


      2. Tom 7 Silver badge

        However working in the infra-red will mean it can see much further through dust that stops visible light. It is hoped it will be capable of being able to see the light from some of the first stars in the universe amongst other things.

        1. Yet Another Anonymous coward Silver badge

          Just to clarify. It sees further in the infrared because the objects it is looking at are so far away and so old hence moving so fast, that their light has been redshifted into the infrared.

  2. Yet Another Anonymous coward Silver badge

    Oh the irony

    When this was being planned back in the 90s the favourite design was a cheap lightweighted 6m conventional mirror, to be launched on the relatively new Ariane 5 with a bulged out fairing

    Then after a change of government it had to be launched on a freedom rocket (instead of a cheese eating surrender rocket) which involved the complex folding design. This took so long and cost so much they had to find european partners who contributed the Ariane 5 launch

    The concern since is whether it will be ready before Ariane 5 is retired

    1. Rich 2

      Re: Oh the irony

      I would think the rocket has already been assigned so even if officially retired tomorrow, they’re not going to change it now - I would think that would be unwise/nuts (disclaimer: I have no idea what I’m talking about)

      1. Yet Another Anonymous coward Silver badge

        Re: Oh the irony

        The launch complex is based around a specific model. If Guiana was upgraded to Ariane 6 it may not be possible to assemble and launch a 5, even if you can find one sitting around in the back of the cupboard.

        The worry was that if JWST was delayed for another 5-10 years there wouldn't be an Ariane 5 for it and re-engineering for a new launch vehicle would be a massive task

        1. Tom 7 Silver badge

          Re: Oh the irony

          I would have thought you could just get an off the shelf adapter to connect a 5 cone to a 6 rocket.

          1. imanidiot Silver badge

            Re: Oh the irony

            The problem is that there are very specific things taken into account when designing a spacecraft for the launch vehicle it's going to ride on. The acceleration profile, launch vehicle vibration profiles and frequency content, sound pressure levels inside the fairing, assembly process and mounting point accessibility, available payload integration tooling and equipment, exact fairing load profile, ground power bus connections, vehicle bus connections, temperature profiles on the ground during payload integration, rollout to the pad, launch prep and during launch, and probably a million more things I don't know about and most people would never think about.

            You can't just plonk JWST onto a Falcon 9 and call it good even if it could fit (which it can't since JWST requires the 5m fairing of the Ariane 5m, while F9 has 4.6m fairings). On top of that you'd need a massive additional dead weight below the telescope since JWST is so light compared to the normal payload weight of F9 that it would accelerate too fast and rip the telescope to pieces. Nor is the F9 second stage really rated to get payloads into the required orbit.

            1. Fruit and Nutcase Silver badge

              The American Job

              Ariane 5F9

              You Were Only Supposed To Blow The Bloody Doors[Fairing] Off!

            2. Fruit and Nutcase Silver badge

              Re: Oh the irony

              On top of that you'd need a massive additional dead weight

              How heavy? Perhaps if it is quantified in meaningful units that we can all understand here...


     many adult badgers?

              1. imanidiot Silver badge

                Re: Oh the irony

                I suspect about 6 skateboarding rhinoceri would cover it.

  3. Red Ted

    So may ways to screw up!

    The nervous tension around this launch and deployment will be very high. There are just so many things that can wrong.

    The sigh of relief when it does get to the L2 point and deploys correctly should be quite audible!

    1. Wexford

      Re: So may ways to screw up!

      If. !! IF !!

      Don't jinx it!

  4. Roger Kynaston Silver badge

    I'll look forward to the Sky at Night episode

    I'm sure Maggie will be delighted to be sent to Guiana assuming travel to S. America is allowed next October.

  5. Mishak Silver badge

    That's a decent overspend

    Would I be right to say there was some "political interest" in this project?

    1. Chas E. Erath

      Re: That's a decent overspend

      This project has kept Northrop Grumman & Ball Aerospace in Fat-City for 20 years - those corporate lobbyists earned their keep with this one. (I think the job was originally pitched by Lockheed.)

  6. Gene Cash Silver badge

    And now Ariane is having fairing problems

    Arianespace acknowledged that “post-flight analyses conducted on two recent Ariane 5 launches have indicated the occurrence of a less than fully nominal separation of the fairing, however with no adverse impact on the Ariane 5 flights in question.”

    1. Fruit and Nutcase Silver badge

      Re: And now Ariane is having fairing problems

      fairing separation...

      see above:

  7. Neil Barnes Silver badge

    there is little scope for a rescue mission

    I see what you did there!

  8. Andre Carneiro

    I'm actually feeling nervous...

    I'm sure I am not the only one, but if a nobody like me is actually feeling nerves about this launch and deployment, I can't even begin to imagine the stress that all the engineering and launch teams must be under right now.

    I can only doff my hat in respect for the sheer boffinry and cleverness going on right now. My mind boggles.

    1. Anonymous Coward
      Anonymous Coward

      Re: I'm actually feeling nervous...

      I don't know how the boffins do it - especially since pipes and Brylcreem aren't allowed in the cleanroom.

      1. Anonymous Coward

        Re: I'm actually feeling nervous...

        Not to mention no more pipes, much less cigars, in Mission Control.

  9. Pete 2 Silver badge

    When unfolding the mirror just remember

    ... shiny side up

    1. Red Ted

      Re: When unfolding the mirror just remember

      ...and which way is 'up' in a zero-g environment?

  10. Anonymous Coward
    Anonymous Coward

    I just hope it won't turn into a giant solar roaster

    Let's see, parabolic mirror, close proximity to the sun.

    Military application?

    Sorry, I've probably seen too much James Bond in my time, but still..

  11. Anonymous Coward
    Anonymous Coward

    Much, much work preceeds such things

    To have an idea of how much work preceeds such adventures, read about the Spitzer:

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