Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

James Webb is fully deployed

nasa.gov

Post reply on HN
Print view View original

221–230 of 522 posts

Re: James Webb is fully deployed

#221

Post by magicalhippo »

ak217 wrote: post #159
WalterBright wrote: post #72

What puzzles me is the maneuvering fuel. When that fuel runs out, the telescope can no longer orient itself. This ended the life of the Kepler telescope. But aren't there other ways to orient in space? 1. use pressure from the solar wind 2. have 3 electric motors on 3 axis. Wouldn't spinning those motors rotate the craft? Electric power to do it would come from solar panels, giving it plenty of fuel.

JWST, like many other spacecraft, has reaction wheels to orient itself. The reason Kepler ran out of fuel when it did was that it was expending more maneuvering fuel for attitude control because two of its four reaction wheels failed. Hubble and the ISS also had similar failures. We're getting better all the time at building more reliable components (including reaction wheels and cryocoolers) though. Until a few year…

> JWST, like many other spacecraft, has reaction wheels to orient itself.

It should be noted that reaction wheels can saturate when the motor reaches its top speed. One then needs to spend fuel to provide a counter-force while the wheel to spins down.

So even with reaction wheels running off solar panels or similar you need fuel, though much less.

Re: James Webb is fully deployed

#222

Post by kragen »

WalterBright wrote: post #206
lisper wrote: post #187

Earlier quoted context omitted.

That's not true. The potential for surprises gets smaller and smaller the more data you collect. The Webb will produce surprises at first because it is able to make new kinds of observations that were not possible before, but after a while that new data will be used to improve our models and subsequent observations in the same regime will (almost certainly) be less surprising as a result.

> The potential for surprises gets smaller and smaller the more data you collect. Mathematically, you are quite correct. But do you really believe that with one little ole' telescope pointed at the freakin' universe you're going to reach a significant point of diminishing returns? It's like saying if you invent the first microscope, and discover bacteria, why bother with another one?

You might see more new things if you spend the next US$4 billion on a different instrument instead of a carbon-copy Lagrange-point infrared telescope. But you're right that you also might not.

Re: James Webb is fully deployed

#223

Post by wrycoder »

surfsvammel wrote: post #209
jl6 wrote: post #192

More great news. Congratulations to all who have worked on the project. I understand the reasons for not putting a camera on or near the JWST, but I’m still a little sad that we’ll probably never get to see the thing in situ in all its operational glory. Maybe one day when it finally expires, we can launch a “sample return” mission to tow it back.

Won't it be pretty close to earth in its final position at L2? If so, is there no chance that there will be future missions to do service to it? If so, maybe we can get a photo of if then?

Maybe Hubble could take a snapshot or two?

Re: James Webb is fully deployed

#224

Post by ThalesX »

MegaDeKay wrote: post #178
micromacrofoot wrote: post #16

Earlier quoted context omitted.

One of the more interesting things that we'll get is data about what's in the atmosphere of exoplanets https://jwst.nasa.gov/content/science/origins.html Note that the next 5 months or so will consist of mirror cooling and calibration, so nothing until summer.

Would you happen to know if they can make intermediate observations while this is in process e.g. observe a relatively nearby object before the telescope is fully cooled and aligned? I'm wondering if they would be able to prove out the optics early on - this is no slam dunk as the Hubble proved.

My knowledge is basically 0, but from what I understood the sensitivity of the sensor is so high, that anything above its operational temperature would overload it and basically make a 'white' image. Basically like having a kitchen scale and then trying to weight an elephant on it (and somehow not breaking the scale in the process).

Re: James Webb is fully deployed

#225

Post by magicalhippo »

Crash0v3rid3 wrote: post #124
davesque wrote: post #91

Earlier quoted context omitted.

I agree with the sentiment, but I think some people might take issue with the suggestion that this was entirely NASA's achievement.

Who else was involved?

https://en.wikipedia.org/wiki/James_Webb_Space_Telescope#Par...

NASA, ESA and CSA have collaborated on the telescope since 1996. [...] ESA is providing the NIRSpec instrument, the Optical Bench Assembly of the MIRI instrument, an Ariane 5 ECA launcher, and manpower to support operations. The CSA will provide the Fine Guidance Sensor and the Near-Infrared Imager Slitless Spectrograph plus manpower to support operations.

Several thousand scientists, engineers, and technicians spanning 15 countries have contributed to the build, test and integration of the JWST. A total of 258 companies, government agencies, and academic institutions are participating in the pre-launch project; 142 from the United States, 104 from 12 European countries, and 12 from Canada. Other countries as NASA partners, such as Australia, have or will be involved in post-launch operation.

Re: James Webb is fully deployed

#226

Post by matheusmoreira »

ThinkBeat wrote: post #189
WalterBright wrote: post #72

What puzzles me is the maneuvering fuel. When that fuel runs out, the telescope can no longer orient itself. This ended the life of the Kepler telescope. But aren't there other ways to orient in space? 1. use pressure from the solar wind 2. have 3 electric motors on 3 axis. Wouldn't spinning those motors rotate the craft? Electric power to do it would come from solar panels, giving it plenty of fuel.

They should have made a port for refueling it. An internal fuel tank and a high-capacity tank externally Once the fuel is getting low, launch a refuel. when the new supply gets closed, eject the previous tank, dock the new one. Easy. When they managed to du an in air refuel of a SR71 in 1970s . Surely we can dock a fuel tank in 2022?

And besides, it works in kerbal space program.

Re: James Webb is fully deployed

#227

Post by richk449 »

WalterBright wrote: post #206
lisper wrote: post #187

Earlier quoted context omitted.

That's not true. The potential for surprises gets smaller and smaller the more data you collect. The Webb will produce surprises at first because it is able to make new kinds of observations that were not possible before, but after a while that new data will be used to improve our models and subsequent observations in the same regime will (almost certainly) be less surprising as a result.

> The potential for surprises gets smaller and smaller the more data you collect. Mathematically, you are quite correct. But do you really believe that with one little ole' telescope pointed at the freakin' universe you're going to reach a significant point of diminishing returns? It's like saying if you invent the first microscope, and discover bacteria, why bother with another one?

I wonder what the optimal number of James Webb space telescopes would be? The cost per unit as a function of number built has been debated, but what about the marginal utility (benefit) ? If you built two instead of one, you would get lots of benefit from the second - an entirely independent set of scientists could decide what to do with it, and maybe explore entirely different subjects. If you made ten thousand of them though, the last one would be nearly useless, because there aren’t enough smart people to make proper use of it. My guess is that after a couple of them, the marginal utility falls off very quickly.

Re: James Webb is fully deployed

#228

Post by jsharpe »

surfsvammel wrote: post #209
jl6 wrote: post #192

More great news. Congratulations to all who have worked on the project. I understand the reasons for not putting a camera on or near the JWST, but I’m still a little sad that we’ll probably never get to see the thing in situ in all its operational glory. Maybe one day when it finally expires, we can launch a “sample return” mission to tow it back.

Won't it be pretty close to earth in its final position at L2? If so, is there no chance that there will be future missions to do service to it? If so, maybe we can get a photo of if then?

It's not that close. The moon is 384,400km away, and JWST will be 1.5 million km away (i.e., around 4x as far as the moon). It would be a pretty serious undertaking to get to it and get back.

Re: James Webb is fully deployed

#229

Post by colechristensen »

surfsvammel wrote: post #209
jl6 wrote: post #192

More great news. Congratulations to all who have worked on the project. I understand the reasons for not putting a camera on or near the JWST, but I’m still a little sad that we’ll probably never get to see the thing in situ in all its operational glory. Maybe one day when it finally expires, we can launch a “sample return” mission to tow it back.

Won't it be pretty close to earth in its final position at L2? If so, is there no chance that there will be future missions to do service to it? If so, maybe we can get a photo of if then?

No L2 is on the further side of the moon.

Maybe when we have active bases on the moon or Mars would a rendezvous with L2 be feasible but not before. Hubble is in low earth orbit and far more accessible.

Re: James Webb is fully deployed

#230

Post by frosted-flakes »

surfsvammel wrote: post #209
jl6 wrote: post #192

More great news. Congratulations to all who have worked on the project. I understand the reasons for not putting a camera on or near the JWST, but I’m still a little sad that we’ll probably never get to see the thing in situ in all its operational glory. Maybe one day when it finally expires, we can launch a “sample return” mission to tow it back.

Won't it be pretty close to earth in its final position at L2? If so, is there no chance that there will be future missions to do service to it? If so, maybe we can get a photo of if then?

L2 is 1.5 million km away. For perspective, the moon is 384 000 km away. That's nearly 4x the distance. It took Apollo astronauts 3 days to reach the moon.
Post reply on HN