The Webb Telescope

@Suzianne
One thing about said debris in L2, they will be captured by the fake gravity well there so they would not be going fast enough to directly penetrate the scope.
They would be moving in a slow orbit, maybe taking weeks to transverse.

@sonhouse said
@jimm619
That is what redundancy is for. The ALWAYS put in redundant circuits so if one poops out, they can switch it via radio.

Redundancy is excellent, but if your weakest link has no redundancy the entire system can quickly fail. That gigantic mirror is far more likely to get damaged than some tiny circuit board, so unless they have redundant mirrors ..... well, you get the drift.

If they haven't planned for some sort of remote robotic repair capability, they should have.

@suzianne said
Said the rocket scientist.

Rocket scientist? How could you possibly know that --- unless --- you are some sort of alien with hyper-human abilities.
Looks like your secret has been exposed. Oops!

@jimm619 said
HUBBLE-------9 ft, mirror
WEBB---------14 ft, mirror

Webb. Over 21’.

The primary mirror, that is.

@bunnyknight
I was one of the techs on Apollo, my gig was Apollo Tracking and Timing' which was about two kinds of tech, timing, atomic clocks, tracking, was a transponder onboard Apollo. We sent data up to the transponder, it rebroadcasts it (the same signal but time shifted because of the speed of light) so when the two signals are compared it figures out how far out the craft is, accurate to within 50 feet. That bit is tripled internally and the timing part, is about getting data from sats around the solar system and the like, because Earth spins, a RF telescope loses signal when the signal goes below the local horizon, all the equipment needed to be sync'd together and that is what our atomic clocks did. But they did not just slap a clock on a table and be done with it, they made TWO separate dups, but with the idea if one went bad, the second one takes over, in about 10 nanoseconds, and if #2 failed it switches to #3 and none of that ever happened on MY watch but it was there.

That is the fundamentals they do there and every other space agency, double and triple redundancy and you can be bottom sure the Webb has it in spades.

You can take that to the bank from a former NASA high tech worker.

The NASA-Site (https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.html) says it is unfolding its forward sun shields.

So we are on schedule.

@ponderable said
The NASA-Site (https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.html) says it is unfolding its forward sun shields.

So we are on schedule.

Excellent site, by the way.

This is very exciting!

@Liljo
I keep fingers crossed, toes crossed, elbows crossed🙂 We have several months before we even know if the dam thing is SETUP right, like mirrors in place, click on the mirror closed up, connected and secure, CLICK.
THEN we wait for a few weeks till the mirrors get down to their operating temperature, some 400 degress F below zero. The good news is they don't need refrigeration for that change, space will do it nicely because the mirror is cooling by radiation so it gradually gets colder.

THEN we worry all the optic sensors pick up the images and the data transfer stuff sends the resultant data back to Earth, BTW, each such transfer which I think they do once a DAY, is about 12 GIGABYTES. Three months of that and they have one TERABYTE of data, 2 years and we are pushing an EXABYTE, a million Gigabytes.
Them is a LOT of data!

@jimm619 said
https://www.npr.org/2021/12/17/1064724045/this-new-space-telescope-should-reveal-what-the-universe-looked-like-as-a-baby?utm_source=pocket-newtab

When I see the price tag I'm always thinking "what if we replaced our military budget with a space budget?"

Answer: we could have hundreds and hundreds of these telescopes and manned missions in the air by the end of the decade.

@venda said
The hubble telescope can't be "repaired" anymore since the space shuttles were de commisioned.
I don't know if they have a strategy for the James Webb

Webb is too far to repair.

@wildgrass said
When I see the price tag I'm always thinking "what if we replaced our military budget with a space budget?"

Answer: we could have hundreds and hundreds of these telescopes and manned missions in the air by the end of the decade.

Yes, but remember,
the lion's share of the
military budget is
retired G.I.'s pensions.

@sonhouse said
@Liljo
I keep fingers crossed, toes crossed, elbows crossed🙂 We have several months before we even know if the dam thing is SETUP right, like mirrors in place, click on the mirror closed up, connected and secure, CLICK.
THEN we wait for a few weeks till the mirrors get down to their operating temperature, some 400 degress F below zero. The good news is they don't need re ...[text shortened]... ERABYTE of data, 2 years and we are pushing an EXABYTE, a million Gigabytes.
Them is a LOT of data!

Got 'em crossed, House Man.
I read where they should start actual use of the scope in 6 months.

That is a LOT of moving parts, and I certainly hope all goes well. This is a very exciting time in the history of mankind. I do wish humanity would focus more on things of this nature than on global, regional, national, and local conflicts. What a world we could have...

@jimm619
I read it as Hubble, 8 ft, Webb, 21 feet. That works out in feet talk, Hubble 50 square feet light collecting area. Webb, ~350 square feet, 7 X Hubble which means at least 7 times the resolution. In terms of arc seconds, Hubble clocks in at about 0.05 arc seconds res, Webb, ~7 MILLI arc seconds res.

Another huge advantage when it starts running, Hubble goes blind half the time it is aimed at something that may take weeks total light gathering time.
That complicates the hell out of reacquiring the target, aiming the scope back on target every hour and a half.
Webb has no such problem so in the same time, say a week staring at a target, it takes Hubble not 7 weeks to get the same light gathered over time, but 14 weeks of observer time because Hubble is in Earth orbit and loses sync on it's intended target requiring finding it again.
So all in all the Webb has effectively 14 times the light gathering power and 7 times the resolution of Hubble.

Pretty impressive specs!

One other thing to note about H Vs W, Hubble was mismanufactured, the mirror was not ground to the right spec so was totally out of whack for astronomy.

The fix was very complex optically AND that assembly did two things:

One, the repair optics in the optic path between some target and the mirror means less light hits Hubble, not a whole lot less but that loss increases slightly the time needed to get X amount of photons on detectors.
The second thing, the corrective optics reduces the effective light gathering power because the whole assembly fits in the space above the mirror but had to sacrifice some of the light collecting area so the effective size for resolution measurements is Hubble lost a few CM of mirror diameter which is a second way to lose design res spec. So even in it's reduced capacity it is better than most all Earth bound scopes.
One huge advantage, IR doesn't penetrate the atmosphere very well so Earthbound scopes have a big strike against them before the scope is even built.
Hubble and Webb won't have THAT difficulty at least and Webb is really going to shine in IR.

@sonhouse
I would have taken a different approach:
Launch 10 Hubble-like telescopes, insert them in the L2 position, and link them all together in a synchronized array. This would increase the resolution and minimize chance of total failure. Also, as time passes more telescopes could be added to this array allowing for infinite growth in resolution.

@bunnyknight
It was ten bil for this one. The Hub cost about 2 billion so ten or so of them will cost about 20 billion. Right now the technology for widely spaced optical telescopes is not quite good enough yet to sync up three or four scopes relatively close, like I think they can't connect sync'd up past something like 100 meters separation, signals are digitized and sent through fiber optics so we could do that but doing just one more could make the res ten times what Webb is touted to be now.
Out there at L2, widely spaced small scopes could certainly compete with Webb but it didn't fly that way.
There still is the matter of light gathering power, Webb totals about 350 square feet of light gathering power so you would need ten scopes each one having 35 square feet of mirror, close enough to use ONE meter mirrors which are a hell of a lot cheaper.
If they could separate and sync them with 9 in a circle around a center scope, like pieces of scope 100 meters in diameter for resolution but still the same light gathering power of Webb. The resulting res would be something like 1 milliarcsecond, or 1000 MICRO arcseconds. One arc second of res parses a circle into 1,2 million bits, so that system would parse out 1.2 BILLION bits.
With that amount of res you could read atmospheres of planets around stars many light years away.
Might even prove the existence of life out there.
I think we will prove life outside Earth might be found right here in either Mars or the giant moons seen to be blowing fans of water vapor a hundred miles or more high and there are plans afoot to run a probe through the fog bank of the stuff coming off deep oceans on the moon like Europa.
I keep waiting for some rover on Mars to come up to a hillside cliff and see a big thigh bone the size of a Mastadon sticking out🙂 Wouldn't THAT cause an uproar.

Massive change in space travel, 15 countries wanting probes on Mars.....

The down side is getting all the small scopes aimed at a target for weeks on end.

Here is one available right now, 1 meter scope, half a million bucks.

https://observatorysolutions.com/planewave-pw1000/?gclid=CjwKCAiAzrWOBhBjEiwAq85QZ69GgHC-tFl6HO7m7kXMjTbQJSFLr0i3PHLj9AxsIVUhFvGFht1dXhoCoJIQAvD_BwE

Obviously this scope would just be a design starting point for one wanting to run for years a million miles from home but these scopes run 5 million for ten.

Then you have to ask what kind of launch vehicle you want to use.

You could have all ten in one craft, say two stories with 5 scopes parked around the perifery on two levels.
So suppose the scope and mirror are 1.2 meters with all the stuff of the scope mounts and such so a 2.4 meter plus say 1.2 meters in center space so about 4 meters wide for the spacecraft, not sure how much space is available in the large cargo rockets but maybe such a project could be done.