NASA is Hosting a Live Press Event for Webb Telescope's Final Major Deployment (nasa.gov) 74
Right now, NASA is providing live coverage for the conclusion of the James Webb Space Telescope's major spacecraft deployments. NASA offered this description of the event earlier this week:
Beginning no earlier than 9 a.m. EST, NASA will air live coverage of the final hours of Webb's major deployments. After the live broadcast concludes, at approximately 1:30 p.m. [EST], NASA will hold a media briefing. Both the broadcast and media briefing will air live on NASA TV, the NASA app, and the agency's website.
As the final step in the observatory's major deployments, the Webb team plans to unfold the second of two primary mirror wings. When this step is complete, Webb will have finished its unprecedented process of unfolding in space to prepare for science operations....
SlashGear reports: Consisting of 18 hexagonal, gold-plated segments, the mirror is one of the telescope's most visually striking components. The primary mirror needs to be large as this is directly related to how much light the telescope can detect, which makes it more accurate (via NASA). James Webb's mirror is 6.5 meters (21ft) across, which is the largest ever launched into space. Compared to the 2.4-meter (7.8ft) mirror used on James Webb's predecessor, the Hubble Space Telescope, this big mirror will help the telescope to see out further into space.
Engineers couldn't just build a 6.5-meter (21ft) mirror like Hubble's, though, because it would be too large and too heavy to launch. Instead, they built the James Webb mirror in segments made from beryllium, which is both lightweight and strong. These segments fold in on themselves to fit into the rocket, and now it is time for them to unfold into their final configuration.
"Once fully operational, Webb will explore every phase of cosmic history," NASA announced, "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."
SlashGear adds that "Having left Earth's atmosphere and traveled over 250,000 miles away from our planet, it is now more than 70% of its way to its final orbit around the sun..."
As the final step in the observatory's major deployments, the Webb team plans to unfold the second of two primary mirror wings. When this step is complete, Webb will have finished its unprecedented process of unfolding in space to prepare for science operations....
SlashGear reports: Consisting of 18 hexagonal, gold-plated segments, the mirror is one of the telescope's most visually striking components. The primary mirror needs to be large as this is directly related to how much light the telescope can detect, which makes it more accurate (via NASA). James Webb's mirror is 6.5 meters (21ft) across, which is the largest ever launched into space. Compared to the 2.4-meter (7.8ft) mirror used on James Webb's predecessor, the Hubble Space Telescope, this big mirror will help the telescope to see out further into space.
Engineers couldn't just build a 6.5-meter (21ft) mirror like Hubble's, though, because it would be too large and too heavy to launch. Instead, they built the James Webb mirror in segments made from beryllium, which is both lightweight and strong. These segments fold in on themselves to fit into the rocket, and now it is time for them to unfold into their final configuration.
"Once fully operational, Webb will explore every phase of cosmic history," NASA announced, "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."
SlashGear adds that "Having left Earth's atmosphere and traveled over 250,000 miles away from our planet, it is now more than 70% of its way to its final orbit around the sun..."
Beryllium is interesting stuff (Score:5, Informative)
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Beryllium is only dangerous if you create dust.
True, but beryllium forms dust easily and must be handled carefully. JWST uses beryllium because it is rigid, but that rigidity makes it brittle. Brittle metals tend to shed dust when handled.
Another reason to use beryllium, besides the obvious lightness, is that it has a low thermal expansion coefficient. So the mirrors can be tested on earth near room temperature and still work in space. It also has very high thermal conductivity, so heat is spread evenly.
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There is a Beryllium Sphere joke in here somewhere, I can just feel it.
No camera (Score:2)
Too bad they couldn't come up with a way to have one or more cameras on the telescope that would allow them to view it directly. The NASA broadcast is just a "visualization" from sensor data. I hear that the deep cold on the telescope side makes cameras impractical there, but it seems like they could have one on a retractable arm sticking out from the sun side.
Re:No camera (Score:5, Insightful)
Any camera, even on a boom wouldn't see anything. It's dark on the telescope side of the sunshield, really really dark. The brightest source of light the mirror will ever see again in its working lifetime will be Mars or maybe Jupiter.
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So you'd need a camera with an LED on it?
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Yeah, an LED that produces zero heat. Got one handy?
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Nope, but I do have an LED that can be pulsed for excruciatingly short periods and still provide useful light. In fact, I have thousands of them.
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You do realize the sensors in this thing are designed to sense about one photon a second, right? Do you really think flooding them with light is a good idea? Oddly, nobody at NASA thought that.
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The sensors aren't "sensing" anything right now, and whatever they did get would have been reflected back from the mirror. There may be some good reasons why there aren't any cameras but this isn't it.
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That's all been addressed elsewhere in this thread. Starlight is adequate illumination for sensitive cameras, and if you don't think so just go outside on a cloudless, moonless night. It ain't pitch dark. For anything requiring more detail an LED light source can do the job. Put a filter on the camera for the sun side.
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Put a filter on the camera for the sun side.
And how would JWST put on a filter on this camera for the sun side and remove it for the other side? Do you propose a complicated mechanism? And after you have designed all of this, for what purpose does NASA need to see the sun side?
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First it couldn't be done, now you claim there's no purpose.
You may need to see your spacecraft in case something goes wrong with it, particularly something you didn't anticipate. That's why Mars rovers have self-inspection cameras, and many other spacecraft as well. Even if you can't fix it you will want to know what failed and why.
Filters of various kinds are automatically inserted in front of cameras in space and elsewhere routinely. There could also be multiple cameras, each of which have a separate kin
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First it couldn't be done, now you claim there's no purpose.
Please cite where I said your request was impossible. I never said that. I relayed to you that there were practical limitations. There always are such limitations. My point again is that your proposed camera would be for a very specific purpose not central to the mission.
You may need to see your spacecraft in case something goes wrong with it, particularly something you didn't anticipate.
NASA does not need to "see" a problem. They need to sense a problem which is the actual solution. You are specifying visual observation as the solution which is the least effective way given the circumstances.
That's why Mars rovers have self-inspection cameras, and many other spacecraft as well. Even if you can't fix it you will want to know what failed and why.
1) Except that the Mars rovers
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Cameras are definitely practical, doable, and desirable as I have shown. Clearly you disagree, at this point I don't care.
Nobody said self-inspection cameras on spacecraft or rovers had to be single purpose, obviously they could do more than one thing. Every rocket that gets sent up these days, every rover, and the ISS have cameras that can view the craft. Webb was designed long ago, and according to the deputy commissioning manager "Webb's multi-decade development began when portable cameras were not widel
Re: No camera (Score:2)
How about using starlight and a reelable tethered webcam? Long exposure shots in the desert look like daylight using starlight.
The Chinese took a selfie on their Tianwen-1 probe.
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Reelable tethered webcam? Sounds like a recipe for crashing the webcam through the sunshield.
Re: No camera (Score:2)
You dont need an LED, starlight is enough. Look at long exposure shots taken at night in the desert .. with a long enough exposure it looks like daylight.
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So you'd need a camera with an LED on it?
https://xkcd.com/2564/
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So you'd need a camera with an LED on it?
Here you ... go [xkcd.com]!
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Okay then, a Braille camera...
Re:No camera (Score:5, Informative)
They thought about, but decided it wasn't worth it. More info here https://blogs.nasa.gov/webb/ [nasa.gov]
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Good article, thanks.
I'm still not convinced that a camera on a moveable boom attached to the sun side couldn't work, but the "not add significant information of value for engineering teams" is a definite hit. As long as the deployment goes well it won't matter. If something gets stuck or hung up it seems like they would want to look at it.
Apparently the entire thing is extensively laced with sensors, switches, and some motors. But that requires wiring, which was a criticism of having cameras.
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Well, yeah, it is laced with sensors, switches, and motors. And they do require wires. But they are also required to make the telescope useful. A camera is not. Adding the wiring for cameras is just increasing the chances for a problem, with little potential benefit.
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Sure would be beneficial if anything goes wrong that the sensors can't diagnose.
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You are welcome to enlighten us with your wisdom, Anonymous Coward. Lots of spacecraft and rovers have self-inspection cameras. Now you can explain why they aren't needed.
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Why? Would having a camera allow them fo fix a problem? Highly unlikely. Now maybe if they were going to launch another one it would be useful to avoid the same problem next time, but it is also highly unlikely that they will launch another one just like this one.
They can't just stick a camera on there for free. There is always a cost, both in money and in things like complexity, power consumption, weight, etc. Suppose they put this extremely limited use camera on there, and the boom for the camera is
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Well, being able to see the problem sure helps me a lot when things get stuck so I expect it would help them too. They already had contingency plans for trying to correct deployment issues, such as shaking the entire craft. Meanwhile, nobody said mounting one or more little cameras would be free. Maybe it would cost a tiny fraction of the billions that were spent.
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I'm still not convinced that a camera on a moveable boom
And every time it moves, the COG changes. And thrusters or reaction wheels need to expend fuel/energy to correct for that. Just for a few space selfies.
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Selfies are interesting to people, and lots of other spacecraft have self-inspection cameras. As for reaction wheels, they run on electricity which the spacecraft gets from solar panels.
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Also the odds of finding a 4 Kelvin capable camera that was low mass, has low power requirements, and is spaceflight rated was probably zero 15-20 years ago when they were designing this thing.
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Extend the camera boom, take photos or video as needed, later retract it. Sum zero. And no need for a "4 Kelvin" camera as was already explained. Cameras have been on spacecraft for decades.
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lots of other spacecraft have self-inspection cameras
In this case (JWST) the cameras would tell you a lot less about the status of mirror deployment than purpose-built position sensors. I'm not sure a camera could sense position to +/- less than a thousandth of an inch which would mean the difference between success and writing the JWST off as junk should deployment fail.
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Nobody said a camera will tell you more about position than position sensors (assuming they are functional). But a camera could tell you what something is hung up on, what is visibly broken, or what got hit by some little space rock a year or so in the future.
Re: No camera (Score:2)
The Chinese had a tiny ejectable camera on their Tianwen-1 probe that took it used to take a selfie.
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The Chinese had a tiny ejectable camera on their Tianwen-1 probe that took it used to take a selfie.
The Chinese didn't have a 69.5 x 49.5 foot sun shield blocking sunlight for their picture.
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The Chinese had a tiny ejectable camera on their Tianwen-1 probe that took it used to take a selfie.
Good heavens - only a Slashdotter would complain that the amazing James Webb doesn't have a selfie camera. And an ejectable camera? there's a lurking problem.
Because of the maggot-gagging expense, and the brinksmanship of the whole project, where a whole lot of of the technology didn't even exist at the time, taking selfies would be a nice stunt, but they decided it wasn't worth it.
Besides, when the JW was conceptualized, selfies weren't a big thing. 8^)
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Surely deep cold is exactly what you'd want. Next to zero thermal noise means you can use a terrifically sensitive device. The cold would prevent steering or a variable lens, but you don't want unnecessary weight anyway.
Now, I could see it from an energy budget POV. Less weight, fewer components that could interact weirdly or go wrong, and less demand on the transmitter means a longer lifespan.
Although there may have been a way to send fuel and coolant by unmanned autonomous vehicle, if longevity was suffic
Re:No camera (Score:5, Interesting)
Great, now you're adding development of a webcam that can function at 4K to the budget.
JWST has a refueling port. What we don't have yet is a vehicle that can approach the telescope without damaging the sunshield or condensing exhaust fumes on the mirrors.
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They did add the refueling port? Cool, it was suggested and initially rejected. I'm glad they reconsidered.
No way (Score:2)
wasting fuel, increasing complexity, wasting bandwidth merely to satisfy people who want unnecessary pictures should not be done.
From a point of view the whole thing is a camera, pretty infrared and low frequency light pictures coming soon enough...
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If it doesn't deploy properly and the sensor suite doesn't say why, I bet they will wish for some cameras.
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Everything has already deployed using the sensors; guess the engineers are smarter than you.
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If it got stuck extended it would ruin, or at least severely degrade, the telescope. Webb takes a lot of necessary risks. It doesn't need unnecessary ones too.
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That wasn't mentioned on their blog as a reason to not include cameras.
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Bit indirect, but the issue is sort of mentioned. The blog post is a pop science journalism thing not an exhaustive risk assessment so that's not really surprising.
The Webb telescope design goes to excruciating lengths to keep the cold side and hot side isolated from each other. The l
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An arm sticking around the shade could be extended and retracted as needed, there are plenty of mechanisms like that on the telescope. And no reason to think it would necessarily reflect sunlight to the cold side, it could have its own small sunshade.
At this point the mirrors have deployed and everything is mostly assembled, which is great but it might not have. Over the course of the telescope's service life however, a lot of things could go wrong where visual inspection would be critical. They decided tak
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Why would visual inspection ever be critical? If the visual inspection shows a problem, what are you going to do about it? And if your answer is they could send some sort of robotic mission to fix it, I am guessing they could also send a mission to get pictures of it if that were absolutely necessary.
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Why would visual inspection ever be critical? Hilarious!
Look buddy, if you have some personal bias against cameras that's fine but I'm tired of arguing with you about it.
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Sure, it would have to be retractable. That's why I said
No, you couldn't give it it's own sunshade. The geometry doesn't work. The sunshade isn't like the umbrella you put up at the beach. It's a highly complex triumph of engineering, designed to allow the telescope to have full, continuous sunlight on one side and be a handful of degrees above abso
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Oh for the luvva god, the camera could just have a simple shield on the sun side, and that would prevent reflection up towards the telescope while it was in use. And yes it could get stuck, but then a couple hundred other useful things also could get stuck as well. Worst case they could just jettison a problematic camera.
I've seen nowhere that they said cameras weren't mounted because it would endanger the mission.
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The jist is that they would need too many to provide useful information about the deployment. A few widefield cameras would complicate the design for no other purpose other then to provide cool visuals for the public.
Re: No camera (Score:2)
The Chinese did it with Tianwen-1
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Why could they not have included a "drone" camera with it's own light source that could be released near the scopes final destination and maneuver it near the telescope to keep an eye on it?
I realize there would be risk of it hitting the telescope if a malfunction, but still...
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Interesting idea. I bet if they designed the Webb today it would have some kind of cameras.
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1. Weight, increasing the weight reduced its lifetime.
2. Complexity, increasing the complexity, increases the risk.
3. Its interesting side is intentionally very dark.
I'm a little puzzled (Score:2)
I'm certain the engineers know what they're doing, but I'm a little puzzled as to why everything is being deployed now, simply because it moves the centre of mass and stuff on arms will experience more stress as the telescope performs braking manoevers to get into position.
It'll be fine and everything will have been built to handle the stresses, I'd just have thought it might reduce fuel consumption and fine-tuning of calculations if deployment was done last.
Re:I'm a little puzzled (Score:4, Insightful)
There are no braking maneuvers. They have to very carefully sneak up on the correct velocity because there is no way to slow down.
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Yes, it is slowing now. But if it goes too fast it can't be slowed because it will crest the gravity 'hills. Once that happens it is game over.
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The telescope has two sets (for redundancy) of thrusters for maintaining orbit around L2, with the amount of propellant determining how long it can be expected to remain in stable orbit. The launching rocket (Arianne 5?) released Webb at about T-5 minutes at a speed of 9.90 km/s (about 6.1 mi/s) for a long coast up the gravity well to a relatively flat spot at L2. Webb is now traveling at a pokey 0.393 km/s (0.244 mi/s) and should basically coast to a near stop at L2.
If you watch the Where's Webb website co
Re:I'm a little puzzled (Score:5, Informative)
They're aiming for a quasi-stable "halo" orbit where the spacecraft will naturally shift around the L2 point with minimal corrections needed. Just for fuel conservation you don't want to do course corrections, you want to aim for approximately correct position and velocity and then just nudge it into place.
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It was designed to be launched on a rocket. The stresses produced by the spacecraft's own thrusters won't amount to much in comparison.
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It'll be fine and everything will have been built to handle the stresses, I'd just have thought it might reduce fuel consumption and fine-tuning of calculations if deployment was done last.
Why would it reduce fuel consumption? There is very little wind resistance in space.
Awesome swag (Score:2)
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there exists some over on etsy. not official tho.
Alternative to the sun shield? (Score:1)