James Webb Space Telescope runs one last dress rehearsal for its massive golden mirrors before heading to launchpad
- Reference: 1620905591
- News link: https://www.theregister.co.uk/2021/05/13/james_webb_last_checks/
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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 in the same way it will in space. The only difference will be the addition of some equipment to simulate the gravity (or lack thereof) of where it will spend its operational life.
The test is the team's final checkpoint in a series of qualifications aimed at ensuring the telescope and its multitude of parts (including the 132 actuators and motors used to deploy and focus the mirrors) will withstand the rigours of launch and a lengthy mission near the Earth-Sun L2 Lagrange point.
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Final checks on Webb's 18 hexagonal mirrors Pic: NASA/Chris Gunn
This is handy because, unlike its predecessor Hubble, there is little scope for a rescue mission should things go south in space. Controllers will face a nail-biting wait from the ignition of the Ariane 5 rocket that's due to launch the telescope to when the telescope completes the trek to its halo orbit around L2 and its systems commissioned.
It has been a lengthy and expensive journey to this point. Originally scheduled to enter service in 2007 at a cost of less than a billion dollars, [3]impressive delays and cost overruns have nudged things to the $10bn mark. Then again, building and launching an observatory of this scale, with ambitions to look for light from the very first stars and galaxies in the universe, does carry its own unknowns.
[4]The ultimate 4-wheel-drive: How ESA's keeping XMM-Newton alive after 20 years and beyond
[5]Once considered lost, ESA and NASA's SOHO came back from the brink of death to work even better than it did before
[6]Out on a tangent: Almost two decades into its 5-year mission, INTEGRAL still delivers the gamma ray goods
[7]20 years deep into a '2-year' mission: How ESA keeps Cluster flying
[8]16 years and counting: How ESA squeezed oodles of bonus science out of plucky Mars Express probe
A final few tests are needed before the observatory is packed up for its trip to Arianespace's French Guiana launchpad. Two radiator assemblies must be extended and restowed and full extension of the [9]deployable tower must be accomplished. The latter, a thick black pipe made of graphite-epoxy composite material, is critical for supporting the structure of the spacecraft and includes two telescoping tubes. It will separate the telescope mirrors from the spacecraft bus.
The delays have meant that the telescope will be launched as the Ariane 5 rocket nears the end of its working life; the veteran booster is to be phased out in favour of the Ariane 6 over the coming years.
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Should all go well, that launch will finally take place just over five months from now, at the end of October 2021. ®
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[1] https://www.nasa.gov/feature/goddard/2021/webb-s-golden-mirror-wings-open-one-last-time-on-earth
[2] https://regmedia.co.uk/2021/05/13/jwstmirrors.jpg
[3] https://www.theregister.com/2019/08/29/james_webb_space_telescope/
[4] https://www.theregister.com/2020/05/01/xmm-newton/
[5] https://www.theregister.com/2020/07/29/esa_soho_space_extenders/
[6] https://www.theregister.com/2020/06/16/esa_integral/
[7] https://www.theregister.com/2020/04/20/esa_space_extenders_cluster/
[8] https://www.theregister.com/2020/03/31/mars_express/
[9] https://www.nasa.gov/feature/goddard/2020/nasa-s-webb-completes-significant-testing-milestone-for-deployable-tower
[10] 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=2YJ1NH631FVxo4C7U2tCN4wAAAI8&t=ct%3Dns%26unitnum%3D2%26raptor%3Dcondor%26pos%3Dtop%26test%3D0
[11] 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=44YJ1NH631FVxo4C7U2tCN4wAAAI8&t=ct%3Dns%26unitnum%3D4%26raptor%3Dfalcon%26pos%3Dmid%26test%3D0
[12] https://whitepapers.theregister.com/
Are you talking before or after COSTAR and the various other fixes to address to monumental screwup of Perkin-Elmer?
The problem is that until it launches we won't know if it can unfold and align itself.
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.
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.
L2 is not 151.1 million km away
You've slipped a couple of decimals, AC. Try [1]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] https://en.wikipedia.org/wiki/Lagrange_point#L2_point
Re: L2 is not 151.1 million km away
I just grabbed the value from the wrong table https://en.wikipedia.org/wiki/Lagrange_point#Solar_System_values
But the point is still the same just 100x less, it is still too far for SpaceX to do maned service mission.
L2 is about 1.5 million kilometers from Earth, not 151 million.
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
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)
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
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.
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!
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.
That's a decent overspend
Would I be right to say there was some "political interest" in this project?
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.”
https://spacenews.com/ariane-5-issue-could-delay-jwst/
there is little scope for a rescue mission
I see what you did there!
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.