James Webb Space Telescope (Technical Post ONLY !)

https://twitter.com/x/status/1474367236244750345
View: https://twitter.com/marinakoren/status/1474367236244750345


Unlike Hubble, Webb isn't designed to be fixed by astronauts. But it can be refueled robotically. Zurbuchen says that "once this telescope is deployed, I'm going to put all the effort towards developing that technology, and so within the 10-year lifespan, we can go refuel it."



A few days ago I asked Bill Ochs, JWST's project manager at NASA, what he would say if Elon Musk offered to try to refuel JWST someday, which would be a very Musk thing to say. Ochs said, "Yeah, go for it."
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https://twitter.com/x/status/1474522449911840769
View: https://twitter.com/wingod/status/1474522449911840769


I was around during some of the debates about this. Dr. John Grunsfeld had Zurbuchen's job then and tried to get a grappling fixture added. He was vociferously opposed, and the science community when JWST was designed did not want crew near it.



The science community hated that Hubble was astronaut upgradable and many of them hated the servicing missions. There is a huge gulf between many in the science community and human spaceflight.
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NASA is shooting for 10 years of operational life from Webb. Engineers deliberately left the fuel tank accessible for a top-off by visiting spacecraft, if and when such technology becomes available.
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apnews.com

Space telescope launched on daring quest to behold 1st stars

The world's largest and most powerful space telescope has blasted off on a high-stakes quest to behold light from the first stars and galaxies.
apnews.com apnews.com
 
Flyaway said:
https://twitter.com/x/status/1474367236244750345
View: https://twitter.com/marinakoren/status/1474367236244750345


Unlike Hubble, Webb isn't designed to be fixed by astronauts. But it can be refueled robotically. Zurbuchen says that "once this telescope is deployed, I'm going to put all the effort towards developing that technology, and so within the 10-year lifespan, we can go refuel it."



A few days ago I asked Bill Ochs, JWST's project manager at NASA, what he would say if Elon Musk offered to try to refuel JWST someday, which would be a very Musk thing to say. Ochs said, "Yeah, go for it."
Click to expand...
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This can explain vey easily. Webb is far, far more fragile and delicate than Hubble.
- it HAS to be extremely cold, and oriented away from the Sun including during its transit phase
- as such, it can't be moved around for servicing
- the sun shield / baffle is also extremely delicate stuff
- it is like a solar sail, except in this case it is a nuisance, as it tends to move the telescope away from its ideal position
- also can't stand any dirty environment / pollution by rocket thrusters or astronaut waste

It essentially boils down to

- infrared astronomy needs - 269°C
- it can be ruined by the telescope own heat (!)
- older IR telescopes were cooled by liquid helium that boiled itself away
- that killed all of them from IRAS 1983 to Spitzer in the 2000's
- Webb is PASSIVELY cooled to -269°C so no He2 supply to run out
- by passive cooling is extremely damn hard and tricky to achieve, even at SEL-2
- in the end between the telescope own heat, its passive cooling absolute need, and the absolute necessity the damn thing never gets warmer than, say, - 268°C - makes servicing of, say, the avionics totally impossible.

It is probably even more subtle and complicated than that.

For example, even a servicing robot will have to control... its own thermal emissions; in a few words, it will have to be designed for -268°C servicing, and darkness, and SEL-2 ops.

Drats, trying to service Webb is a bit like Count Dracula in sudden need to go out in, say, the Sahara desert at noon. If sun light touches it, it's GAME OVER.
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Q&A: NASA Administrator Bill Nelson talks big moments of 2021 and what's next in 2022

FLORIDA TODAY: If everything goes well with Webb's incredibly complex deployment process, do you see continued participation from the public and Congress when it comes to future space telescopes? We saw something similar when Hubble came online and delivered the riveting Hubble Deep Field image with thousands of galaxies.

Nelson: Yes, but mind you, this thing has a design life of up to 10 years. But we are also developing the capability of on-orbit servicing. That includes refueling. We have the capability in the next 10 years, before Webb runs out of fuel, to go up there and refuel. So instead of a 10-year life, it could continue to give us information on and on just like Hubble has.
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Flyaway said:
Webb has extra fuel because of an accurate launch - fuel for longer than 10 years of science.

NASA Says Webb’s Excess Fuel Likely to Extend its Lifetime Expectations – James Webb Space Telescope

blogs.nasa.gov blogs.nasa.gov
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I expected this. The official 10.5 years was always supposed to be "likely worst case" so a near-nominal launch would save hydrazine that they can use for the MRE thrusters later.

I like that this article also explains the early solar panel deployment -- Ariane was so close to the intended track that the panels didn't have to wait until the timed deployment at L+33.
 
TomS said:
Flyaway said:
Webb has extra fuel because of an accurate launch - fuel for longer than 10 years of science.

NASA Says Webb’s Excess Fuel Likely to Extend its Lifetime Expectations – James Webb Space Telescope

blogs.nasa.gov blogs.nasa.gov
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I expected this. The official 10.5 years was always supposed to be "likely worst case" so a near-nominal launch would save hydrazine that they can use for the MRE thrusters later.

I like that this article also explains the early solar panel deployment -- Ariane was so close to the intended track that the panels didn't have to wait until the timed deployment at L+33.
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That is extremely good news for the James Webb, I had originally thought that the Webb would have only enough onboard fuel for a five year mission at least, so the astronomers won't need to rush tho get their telescope time.
 
FighterJock said:
That is extremely good news for the James Webb, I had originally thought that the Webb would have only enough onboard fuel for a five year mission at least, so the astronomers won't need to rush tho get their telescope time.
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Five years seems to have been worst worst case -- if basically everything went wrong that could go wrong and still have an operational telescope. Twn years was the planning goal. I doubt they could have gotten the project approved if 5 years was a likely number.

It will probably still be like Hubble, where observing time is desperately fought over, because there are lots of grad students fighting for a very small number of opportunities.
 
I am going to ask what might be a silly question. Why would it not have been practical to put the Webb into lunar orbit for deployment, where we might have been able to fix any issues that might come up (I remember the hobbled Hubble) before putting it out in deep orbit? Fuel/weight? Solar damage?
 
yasotay said:
I am going to ask what might be a silly question. Why would it not have been practical to put the Webb into lunar orbit for deployment, where we might have been able to fix any issues that might come up (I remember the hobbled Hubble) before putting it out in deep orbit? Fuel/weight? Solar damage?
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Heat. It's sitting at the Sun-Earth L2 point because that allows it to keep the Sun and Earth in the same direction and block both with one sunshield. If it was closer in, you'd need to protect it from both solar heat and heat from Earth, requiring more shields and/or a lot more maneuvering.

webb.nasa.gov

Orbit - NASA Science

webb.nasa.gov webb.nasa.gov

Edit: I just reread and see what you're saying about initial deployment. For that, well, the energy budget to put in lunar orbit first and then change to the L2 is pretty big. Plus, there's really no way to send people to the moon for repairs anyway. And the vehicle is incredibly fragile. The sensors pretty much have to remain permanently in shadow to avoid being destroyed, I doubt there's a lunar orbit that can do that.
 
yasotay said:
I am going to ask what might be a silly question. Why would it not have been practical to put the Webb into lunar orbit for deployment, where we might have been able to fix any issues that might come up (I remember the hobbled Hubble) before putting it out in deep orbit? Fuel/weight? Solar damage?
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The short answer to your question is that NASA shut down the Shuttle program ten years ago and since then there has been no way of getting the James Web fixed if things start to go wrong Hubble wise, so it would be impossible to send Astronauts out to the Lunar Orbit anyway.
 
Thank you both for what I suspected was the answer. While we currently have no way to get to the moon to fix problems, there does seem to be "a" way to get there in the next few years. I would think it is significantly more difficult to go to L2 in a "timely" manner to conduct repair. But as mentioned with the sensitivity of the instruments, prolonged lunar orbit would likely render repair superfluous.
 
FighterJock said:
yasotay said:
I am going to ask what might be a silly question. Why would it not have been practical to put the Webb into lunar orbit for deployment, where we might have been able to fix any issues that might come up (I remember the hobbled Hubble) before putting it out in deep orbit? Fuel/weight? Solar damage?
Click to expand...

The short answer to your question is that NASA shut down the Shuttle program ten years ago and since then there has been no way of getting the James Web fixed if things start to go wrong Hubble wise, so it would be impossible to send Astronauts out to the Lunar Orbit anyway.
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The Shuttle couldn't have gotten a repair team to lunar orbit even when it was active. It could barely reach Hubble, which was right up at the limits of the Shuttle's performance.

As Yasotay alluded to, it would take Artemis-like systems (including Orion) to get to lunar orbit. And JWST can't survive in lunar orbit anyway.

There are some hopes that they could do a robotic refueling mission some time down the road to extend the JWST's observing life, but that's very speculative right now. Even a refueling vehicle would have to take extreme measures to avoid damage to the instruments.
 
As @TomS said. Plus this https://www.thespacereview.com/article/688/1

Infrared astronomy hates any thermal emissions, including from the telescope itself. It's -269°C or bust.

Early IR telescope like IRAS to Spitzer had a dewar of liquid helium at -268°C that took the telescope heat away... by boiling up. Once the helium supply exhausted, the IR telescope got warm and partially blind.

en.wikipedia.org

Spitzer Space Telescope - Wikipedia

en.wikipedia.org en.wikipedia.org

Spitzer was launched in 2003, ran out of helium in 2009, but they performed a "warm" mission until last year, 2020.

Webb is one of the first to cool itself without any helium, removing a major life limit of spaceborne IR telescopes.

But it paid some price to that
- SEL-2 1 million miles from Earth
- don't move by an inch otherwise the Sun ruins the day
- it is so damn cold everywhere, no maintenance (Hubble style) is possible except perhaps refueling by a robot.
 

Webb’s Deployable Tower Assembly Extends in Space​

This afternoon, the Webb team successfully extended the observatory’s Deployable Tower Assembly (DTA), creating critical distance between the two halves of the spacecraft.

The DTA extended about 48 inches (1.22 meters), putting room between the upper section of the observatory, which houses the mirrors and scientific instruments, and the spacecraft bus, which holds the electronics and propulsion systems. This creates enough distance to allow the sensitive mirrors and instruments to cool down to the necessary temperatures to detect infrared light. This gap will also provide room for the sunshield membranes to fully unfold.

The deployment took more than six and a half hours, as engineers activated release devices and configured heaters, software, and electronics, before commanding the DTA itself to extend. The movement of the DTA, which looks like a large, black pipe, is driven by a motor. The team began the deployment at approximately 9:45 a.m. EST and completed it at approximately 4:24 p.m. EST.

This step furthers the team’s progress in deploying Webb’s sunshield – a human-controlled, multi-day process that will continue with the release of aft momentum flap and the sunshield covers.

Webb’s Deployable Tower Assembly Extends in Space – James Webb Space Telescope

blogs.nasa.gov blogs.nasa.gov
 
Webb’s Aft Momentum Flap Deployed

Shortly after 9 a.m. EST today, the Webb team completed deployment of the observatory’s aft momentum flap. In a process that took about eight minutes, engineers released the flap’s hold-down devices, and a spring brought the flap into its final position.

The aft momentum flap helps minimize the fuel engineers will need to use throughout Webb’s lifetime, by helping to maintain the observatory’s orientation in orbit. As photons of sunlight hit the large sunshield surface, they will exert pressure on the sunshield, and if not properly balanced, this solar pressure would cause rotations of the observatory that must be accommodated by its reaction wheels. The aft momentum flap will sail on the pressure of these photons, balancing the sunshield and keeping the observatory steady.

Just as a ship’s mast must be set in position and the rigging established before the ship unfurls its sails, Webb’s pallet structures, momentum flap, and mid-booms will soon all be in place for Webb’s silver sunshield to unfold. The next steps in Webb’s planned deployment timeline are outlined here.
 
"Webb’s engineers have released and rolled up the sunshield covers that protected the thin layers of Webb’s sunshield during launch. After the team electrically activated release devices to release the covers, they executed commands to roll the covers up into a holding position, exposing Webb’s sunshield membranes to space for the first time.

The deployment, which took about an hour, concluded at approximately 12:27 p.m. EST.

In their next stages of planned activities, engineers will deploy the sunshield mid-booms, before proceeding with sunshield tensioning."

Webb Team Releases Sunshield Covers – James Webb Space Telescope

blogs.nasa.gov blogs.nasa.gov
 
December 30, 2021
MEDIA ADVISORY M21-171
NASA Plans Coverage of Webb Space Telescope Deployments

Thousands of parts must work correctly, in sequence, to unfold NASA’s James Webb Space Telescope into its final configuration, all while it flies to a destination nearly 1 million miles away.
Credits: NASA/Chris Gunn
Over about the next two weeks, NASA will provide broadcast coverage, a media briefing, and other updates on major deployment milestones for the James Webb Space Telescope, the world’s largest and most powerful space science telescope.
Broadcasts of milestone events will air live on NASA TV, the NASA app, and the agency’s website.
Webb, an international partnership with the ESA (European Space Agency) and the Canadian Space Agency, launched Dec. 25 from Europe’s Spaceport in Kourou, French Guiana. The observatory had been folded up, origami style, to fit inside an Arianespace Ariane 5 rocket for launch. Webb is now in the complex and intricate process of unfolding in space, as it travels nearly 1 million miles to its destination, the second Lagrange point or L2.
Webb’s deployment sequence is a human-controlled process that provides the team with the flexibility to pause, assess data, and adjust as needed. The timing and order of all milestones may therefore change. NASA will host live broadcast coverage to mark the following milestones, with specific times and dates updated as they approach:
•Sunshield tensioning: The full deployment of the sunshield, the most challenging element for Webb, will mark a critical milestone for the mission. This step is scheduled for completion about eight days after launch, no earlier than Sunday, Jan. 2.
•Secondary mirror support structure deployment: The support structure that holds the secondary mirror in position to focus light collected by the primary mirror is set for deployment about 10 days after launch, no earlier than Tuesday, Jan. 4.
•Webb deployments complete: With the unfolding of the second of Webb’s primary mirror wings, the Webb team will have completed all observatory deployments. This is scheduled to take place about 13 days after launch, no earlier than Friday, Jan. 7.
NASA provides regular updates on the Webb telescope blog. The public can also follow Webb’s deployments online via a “Where is Webb?” interactive tracker and a Deployments Explorer.
NASA Press Briefing
NASA will hold a media briefing as soon as possible after the end of the live broadcast coverage of Webb’s final deployments. The agency will determine the timing of this briefing as final deployments approach and stream the event live on its website.
NASA’s media accreditation policy for virtual activities is available online.
Social Media Engagement
Members of the public can stay connected with the mission and let people know about Webb’s deployments on Twitter, Facebook, and Instagram with #UnfoldTheUniverse. Follow and tag these accounts:
•Twitter: @NASA, @NASAWebb
•Facebook: NASA, NASAWebb
•Instagram: NASA, @NASAWebb

Additional Webb Resources:
•Digital media kit
•Image and video galleries
•Media interview request form
The Webb mission will explore every phase of cosmic history – from within the solar system to the most distant observable galaxies in the early universe, and everything in between. Webb will reveal new and unexpected discoveries and help humanity understand the origins of the universe and our place in it.
For more information about the Webb mission, visit:
-end-
Press Contacts
Alise Fisher / Natasha Pinol
Headquarters, Washington
202-358-2546 / 202-358-0930
alise.m.fisher@nasa.gov / natasha.r.pinol@nasa.gov
Laura Betz
Goddard Space Flight Center, Greenbelt, Md.
301-286-9030
laura.e.betz@nasa.gov
 
Flyaway said:
The science community hated that Hubble was astronaut upgradable and many of them hated the servicing missions. There is a huge gulf between many in the science community and human spaceflight.
Click to expand...
Click to expand...
My guess is that Webb could have been simpler had they got behind HLLVs earlier. Good that Ariane overperformed-old space's best moment. Can anything be done with the spent upper stage? Where is it now? In the future, maybe it could block a star like an ersatz sunshade?
 
publiusr said:
Flyaway said:
The science community hated that Hubble was astronaut upgradable and many of them hated the servicing missions. There is a huge gulf between many in the science community and human spaceflight.
Click to expand...
Click to expand...
My guess is that Webb could have been simpler had they got behind HLLVs earlier. Good that Ariane overperformed-old space's best moment. Can anything be done with the spent upper stage? Where is it now? In the future, maybe it could block a star like an ersatz sunshade?
Click to expand...
AIU, the upper stage is on an escape trajectory, so it'll end up in a heliocentric orbit between Earth and L2.
 

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