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The James Webb Space Telescope Has Emerged From the Freezer (arstechnica.com)
The James Webb Space Telescope has emerged from a large vacuum chamber that was home to temperatures of just 20 degrees Celsius above absolute zero. Scientists have reviewed the data and given the instrument a clean bill of health. "We now have verified that NASA and its partners have an outstanding telescope and set of science instruments," said Bill Ochs, the Webb telescope project manager at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "We are marching toward launch." Ars Technica reports: The $10 billion telescope underwent tests inside Chamber A at Johnson Space Center, which was built in 1965 to conduct thermal-vacuum testing on the Apollo command and service modules. Beginning in mid-July, after the telescope was cooled down to a temperature range of 20 to 40 Kelvin, engineers tested the alignment of Webb's 18 primary mirror segments to ensure they would act as a single, 6.5-meter telescope. (They did). Later, they assessed the fine guidance system of the telescope by simulating the light of a distant star. The Webb telescope was able to detect the light, and all of the optical systems were able to process it. Then, the telescope was able to track the "star" and its movement, giving scientists confidence that the Webb instrument will work once in space. Webb still has a ways to go before it launches. Now that project scientists know that the optic portion of the instrument can withstand the vacuum of space, and the low temperatures at the Earth-Sun L2 point it will orbit in deep space, they must perform additional testing before a probable launch next year.
Mixing Celsius and Kelvin in the same unit of measure.
Your comment is useless.
The submitter stated that the telescope was being kept at a temperature of 20-40K. And 0K is absolute zero.
A difference of 1K is equivalent to 1degC. They're the same thing. If the telescope was kept around 20degC above absolute zero, which BeauHD added, it's the same thing.
By the way, scientists mix degC and K quite frequently. We tend to measure temperatures in degC in most situations in our everyday lives. However, many of the equations are derived to work with K as their unit. The ideal gas law is an example of such an equation. When you use that equation, you use the Kelvin scale. However, you would likely report the temperature to others using the Celsius scale, which simply involves subtracting 273.15.
Why doesn't Slashdot delete spam like the parent comment? Slashdot has deleted plenty of comments, so I'd really like to know why the GNAA spam gets a free pass.
Such a waste of money for some scientific nonsense! Can you imagine how many miles of beautiful big, really beautiful border wall we could have for $10B? At least 2 or 3 miles of big beautiful wall!
L2 is in the earth's shadow. It will orbit around L2 in such a way that it is never in the earth's shadow but also so that it's sun shield will block light from the earth, the moon and the sun. It will also be about 6 times further from the earth than the moon.
That vacuum chamber cum fridge was made 53 years ago, in 1965
How many of our current appliances can still be in working order 53 years from now?
Is our civilization really progressing, or have we started the never-ending journey of descent?
“The James Webb Space Telescope has emerged from the freezer” is one of the worst secret recognition codes I’ve heard in a long time. People are going to notice that one!
#DeleteChrome
It was out of the freezer before Christmas. My wife works at JSC and we waited in line for 4 hours to see it back on Dec. 20.
... to its final orbit (and been commissioned and been tested and is sending back science data). And then Iâ(TM)ll worry that itâ(TM)s running out of its consumables too quickly or its gyroscopes are failing at a higher than predicted rate.
These multi-billion dollar space science projects always put me on edge, especially one like this which is so far from earth that there are no easy repair scenarios such as the one that saved Hubble. Too bad that it wonâ(TM)t be unfolded and tested in LEO (so that it would have at least the possibility of being fixed). Of course then it would probably then need an ion drive in order to (very slowly) get it to L2 because the delicate unfolded mirrors couldnâ(TM)t possibly maintain their precision with a chemical rocket.
Anyway, hereâ(TM)s hoping that Elon can bring the cost of space flight down by a factor of ten or more so a repair mission to L2 wouldnâ(TM)t be prohibitively expensive. Also if getting things to orbit werenâ(TM)t so expensive maybe a much bigger telescope (possible because it would just entail more mirror modules right?) could be sent because they wouldnâ(TM)t have to worry about shaving every gram off. The reduced constraints on weight might also allow for a more robust safer and cheaper design.
So everything will be helped out a lot by cheaper access to space! (Captain Obvious)
... And then it will be blown to smithereens by a faulty launch vehicle.
These multi-billion dollar space science projects always put me on edge, especially one like this which is so far from earth that there are no easy repair scenarios such as the one that saved Hubble.
If we never go beyond repair range it's going to take an awfully long time to do anything useful in space. Gotta take some risks sooner or later.
Anyway, hereâ(TM)s hoping that Elon can bring the cost of space flight down by a factor of ten or more so a repair mission to L2 wouldnâ(TM)t be prohibitively expensive.
I think a better idea is to learn to make things that don't need repair missions. Harder task to be sure but necessary if we really want to explore our solar system in a serious way.
"20 degrees Celsius above absolute zero" - this formulation hurts
Silly me. I thought it was unfolding in space already
The James Webb Space Telescope has emerged from a large vacuum chamber that was home to temperatures of just 20 degrees Celsius above absolute zero. Scientists have reviewed the data and given the instrument a clean bill of health.
I guess 20 Kelvin was too "scientific" to be used instead of "20C above absolute zero".
Elok
How do they test it for surviving the 9G ascent?
So trolling with idiot goddamned smartquotes is a thing now?
And I take it the canonical retort is "stop posting from your iphone".
the preceding comment is my own and in no way reflects the opinion of the Joint Chiefs of Staff
I guess the people who say "20 kelvin" like to go home and listen to their sound system powered by an amplifier which delivers 100 watt and is plugged into a wall outlet which puts out 120 volt.
OK, time to pop it on top of a rocket and loose it.
I hope it can get out there and do some amazing science, but it is a disturbingly expensive telescope and its not even off the ground yet. It is known by some as the "telescope that ate astronomy". Its continuing cost overruns have delayed/canceled several other science projects. In hind-site it should have been canceled the first time it surpassed its budget by an order of magnitude, let alone the six times its budget its up to so far (originally estimated at $1.6 B).
You crazy. But this is slashdot and so it's easy to pass for normal here.
I suggest you spend next Christmas in Uruguay or Australia.
If the summer day and winter day had identical atmospheric conditions (and uniform, or equivalent when accounting for different Sun azimuth) then it would appear the same.
However, the summer atmosphere is likely very different from the winter atmosphere. I terms of optical properties that influence Sun appearance: moisture content (humiditity) and visibility scattering (fog/mist/haze), turbidity, dust or particulates due to season-dependent crops, pollen or other biological factors. The temperature difference may also allow different refraction (minor), or different altitude falloff functions for Mie or Rayleigh scattering due to different air density and relationships buoyancy of participating media. Any of these can affect the ground-level spectral radiance (and therefore luminance and chromaticity, is “brightness and color”) of the Sun observed at your location, and also that of the surrounding sky.
And of course winter skies normally have big ol’ grumpy clouds and rainabdstuff flying around, but I assume you’ve allowed for that difference.
Apart from that, yes, summer and winter skies should look identical.
Maybe there’s a chemical plant south east of you? Would explain the different colours you see, especially if the wind is a south-easterly...
None of what you say makes any sense, by the way. I don’t meant to sound rude, but I’m guessing you weren’t top of the class in science?
If that was the case, then sunsets and sunrises would look completely different in the same day, because one would be going into a heated atmosphere, and the other into a cooled atmosphere.
Of course it makes no sense. If it did make sense to you, you'd already know it.
Everything is eventually going to run out of propulsion gas for maneuvering, no matter how big you make the tank.
What is your point exactly? Should we have not sent the Voyager probes because they can't maneuver anymore? Missions don't have to last forever and it's certainly possible to design robotic refueling missions for those where refueling is appropriate. What we shouldn't do is design spacecraft such that they need unnecessary amounts of servicing. Hubble is a great spacecraft but it required more servicing than it really should have. Limiting ourselves only to missions where servicing is comparatively easy is going to slow us down quite a lot.
I'm not saying it's never appropriate to design a mission where servicing the spacecraft is necessary. But I think it is something to be avoided whenever possible. Any mission beyond low Earth orbit is going to be a problem to service so we might as well learn how to do high reliability as soon as possible.