James Webb Space Telescope

[MeteorWayne]

BTW, depending on developments over the next few weeks it may be a moot point. It's certainly possible the mission will be cancelled for lack of funding.

 

[MeteorWayne]

Bill, you should expend some effort understanding the difference between the L1 (closer to the sun), L2 (away from the sun, L3 (oppisite the sun) and L4 and L5, where the trojans reside. They have different levels of stability, and different populations of objects that stay there.

To suggest that L2 is as populated as the L4 or L5 points shows you need to do some more basic research.

 

[Kansan52]

I'm surprised that no one pointed out that the American antisatellite test was done to minimize any space debris load.

No satellite could be retasked in the manner described. Even for testing purposes. Sure be nice if it could.

If the leaked material from Obama's AntiNasa commission is correct, all options replacing Ares I costs extra billions (that Congress won't give) and push things to the right by years (even with extra money). (Bet the knowledge of Obama's plans for Nasa is what caused Griffin to flee and why nobody else wanted the job.)

Both Bigelow and Space X testified their plans cannot replace Constellation. Both Dragon and Orion Lite are designed for low earth orbit. They are truly amazing programs and will be great assets for the ISS and Bigelow's planned lab. Using these resources should help Nasa by easing it's LEO obligations.

 

[silylene]

I'm surprised that no one pointed out that the American antisatellite test was done to minimize any space debris load......

Please explain what you mean.

Actually the recent US antisat test on USA193 was a very STUPID thing to do. It created a huge debris cloud when the hydrazine tank blew up. Despite being in low earth orbit, some of the debris fragments were unexpectedly hurled into high orbits, where they pose a danger to other satellites and even spacecraft. I also recall some of the fragments in low earth orboit posed a slight threat to the shuttle during its atmospheric re-entry. We had a good thread on this in the forums.

You need to read the science reports on this, not the political statements, one-sided views from the Pentagon, or the adulatory press from FOX and even some of the other news outlets.

 

[Bill_Wright]

MeteorWayne wrote: "Bill, you should expend some effort understanding the difference between the L1 (closer to the sun), L2 (away from the sun, L3 (oppisite the sun) and L4 and L5, where the trojans reside. They have different levels of stability, and different populations of objects that stay there. To suggest that L2 is as populated as the L4 or L5 points shows you need to do some more basic research."

Well, MW, I disagree. That is like saying that since you didn't spell check your reply it has no validity. I identified the position correctly and indicated I didn't care to look up the number. Never did I suggest that the population of these points were even closely identical, simply that the odds of finding dust there was larger than in regions of space that did not have these particular properties. And other than water vapor (unlikely to find much of that in space), dust is cruel to infrared observations. Since you have already pronounced JWST dead in a previous reply in this thread why don't we drop it. We have SOFIA to get some IR data and when they sell whatever they have built of the JWST on eBay or a scrap yard I just hope I get a chance to bid on it. I know of at least one place on Earth that will allow it to take better pictures than my 40 year old (about) Celestron.

 

[MeteorWayne]

MeteorWayne wrote: "Bill, you should expend some effort understanding the difference between the L1 (closer to the sun), L2 (away from the sun, L3 (oppisite the sun) and L4 and L5, where the trojans reside. They have different levels of stability, and different populations of objects that stay there. To suggest that L2 is as populated as the L4 or L5 points shows you need to do some more basic research."

Well, MW, I disagree. That is like saying that since you didn't spell check your reply it has no validity. I identified the position correctly and indicated I didn't care to look up the number. Never did I suggest that the population of these points were even closely identical, simply that the odds of finding dust there was larger than in regions of space that did not have these particular properties. And other than water vapor (unlikely to find much of that in space), dust is cruel to infrared observations. Since you have already pronounced JWST dead in a previous reply in this thread why don't we drop it. We have SOFIA to get some IR data and when they sell whatever they have built of the JWST on eBay or a scrap yard I just hope I get a chance to bid on it. I know of at least one place on Earth that will allow it to take better pictures than my 40 year old (about) Celestron.

Bill, I never pronounced the JWST dead, I merely suggested it's in trouble as is in fact everything in NASA's ballcourt. The fact is, NASA is not being funded at a sustainable level for the projects in the pipeline. We'll find ou a bit more tomorrow.

Also, as pointed out, the JWST is not to be placed at the L2 point, in fact is in a huge orbit around it. Also as pointed out, L1, L2, and L3 are not dynamically stable, so there is no reason to expect higher dust concentrations there than anywhere else in space.

L4 and L5 are a different story.

 

[Hiberniantears]

MeteorWayne wrote: "Bill, you should expend some effort understanding the difference between the L1 (closer to the sun), L2 (away from the sun, L3 (oppisite the sun) and L4 and L5, where the trojans reside. They have different levels of stability, and different populations of objects that stay there. To suggest that L2 is as populated as the L4 or L5 points shows you need to do some more basic research."

Well, MW, I disagree. That is like saying that since you didn't spell check your reply it has no validity. I identified the position correctly and indicated I didn't care to look up the number. Never did I suggest that the population of these points were even closely identical, simply that the odds of finding dust there was larger than in regions of space that did not have these particular properties. And other than water vapor (unlikely to find much of that in space), dust is cruel to infrared observations. Since you have already pronounced JWST dead in a previous reply in this thread why don't we drop it. We have SOFIA to get some IR data and when they sell whatever they have built of the JWST on eBay or a scrap yard I just hope I get a chance to bid on it. I know of at least one place on Earth that will allow it to take better pictures than my 40 year old (about) Celestron.

Bill, for someone who has your claimed background, I'm somewhat surprised at your statements. Antarctica is still on planet Earth. No part of Antarctica is Australian territory, although like Australia, Antarctica is also located inside our atmosphere, which is full of continental dust, water vapor, and other assorted gases and particulate. Space is full of dust as well, but orbiting the L2 point at a massive distance will not place the JWST inside of an opaque (for IR) cloud of dust, debris, or asteroids. Basic physics are not the only reason that L2 was chosen as a parking spot for this telescope.

It kind of seems like you're just mad at NASA in general, rather than actually concerned about this telescope. That's fine too, because the Republicans and the Democrats have made a mess of the agency since the 1970's. But this isn't really the fault of NASA, so much as a disinterested electorate. NASA is merely a reflection of how interested Americans are in space. As you can see, there ain't that much interest these days in watching some lame video of an astronaut blow a floating bubble of water around, because it only serves as a graphic reminder that human spaceflight is currently a gigantic waste of money. 486 people have ever reached low earth orbit. 24 people have flown beyond that. Nobody has flown beyond the moon. That is a pathetic failure.

 

[wxgeek]

Hey Bill,

I have wondered about this myself for a long time. I can imagine the L points as little dust clouds. Sure if an object that is cruising along and entered an L point would just continue on. But, I feel your point is valid. I would think a NASA program would go and inspect these areas for debris or just to see what is there before you place a very expensive piece of hardware there. It is possible it will be a great place and it may not be an issue but I think the unknown factor seems high to me.

Antarctica is not a bad place to put a telescope. Of course, it does limit you on where you can look. The Arctic would be fine for the northern half of the sky. The nice think about the polar regions is the atmosphere is actually thinner. Meaning the tropopause is about half as high above sea level than the equator ( 8km vs. ~18 km at the equator). It would not be an easy environment to work and there is still some things the atmosphere would filter out that might be desirable to see without any air filtration.

 

[MeteorWayne]

Look, folks, this whole thread is a tempest in a teapot. There are currently 3 operational spacecraft at L2. WMAP has been operating there since October 2001 (8 years). It's not like we haven't examined the area. Herschel and Planck are beginning scientific observations there now. Best case, the JWST will launch in 4 years or so.

So let's just get a reality check here, OK?

 

[centsworth_II]

...I can imagine the L points as little dust clouds....

I can see some members here pulling their hair out at this point! :lol:

But I'll try again. For some reason, you and Bill insist on taking what is known about L4 and L5 and applying it to L2 which is very different from L4 and L5 where dust accumulates. Dust DOES NOT ACCUMULATE at L2.

According to the European Space Agency http://www.esa.int/esaSC/SEMM17XJD1E_index_0.html:
"Unlike the other Lagrange points, L4 and L5 are resistant to gravitational perturbations. Because of this stability, objects tend to accumulate in these points, such as dust and some asteroid-type objects."

And... "L2 is a great place from which to observe the larger Universe."

The Europeans have two spacecraft at L2 as we speak and NASA has had a craft there for the past EIGHT YEARS!!! Why do you and Bill act like Webb is pioneering unknown territory?

 

[michaelmozina]

Hi:
I think we might be getting ready to make a big mistake. We have spent a lot of money building this scope and plan to launch it into one of the Lagrangian Points, I think the one with the Earth between it and the Sun. Nobody has done a survey of these points near Earth to ascertain how full of rocks and dust they might be. I think there are similar areas called Trojans around Jupiter that are known to have big rocks and can be assumed to have particles right down to the size of tiny dust.

Now just recently a survey of Antarctica done by the Australians and Americans turned up a plateau in "Australian Territory" that is considered to have "seeing" pretty close to that of the HST. Why don't we put the Webb scope there and test it out until we insure that there will be no problems in its intended "parking spot"? We would learn many lessons about operating in harsh environments (this is one of the coldest spots on Earth), minimize risks in making a mistake, get some awfully good science done, and save a ton of money as the folks who work in Antarctica tend to do so for the love of the place, not money. If it turns out that the concern is unfounded, then we just pick up the scope, call it an extended ground test, and launch it to L1 (or 2, 3, 40 - whatever). I'm sure that some politicos could put a real positive spin on this so nobody but us would be the wiser.
Bill

It seems to me that there is room for both ground based observatories and space based observatories and they compliment each other very nicely.

I can relate somewhat to your concern about making sure the equipment is iin good working order before it goes into space, especially after Hubble needing glasses and all, but the notion of shipping it off the the outback for testing hardly seems practical. I see that MW and others already addressed that issue.

IMO your concern about the environment it will experience is somewhat misplaced. Space is a very hostile environment to begin with and there are no "guarantees" in space. It could get hit with an intense CME right after launch, but that's life in space. We take our risks but the payoffs have been well worth it. Hubble changed astronomy and I'm sure it's replacement will change it some more.

With all the stupid things that our governments spend our money on these days, it's nice that we actually do have space programs that give us a real return on our investment. Personally I'm for spending money on both ground based equipment, and for equipment designed for space. Recent space satellites like Yohkoh, Geos, SOHO, Trace, Hinode, STEREO, Chandra, Hubble, Spitzer and Ibex have fundamentally changed our understanding of the physical universe around us. All of them put together didn't equal a couple of monthly payment to the "federal reserve" to pay off the interest alone for the bank bailouts of the last two years. Keep the satellites. Just say no to Citibank.

 

[Bill_Wright]

Hi --
Some of you seem to be confused and think this scope should be placed in the 'outback'. Please read this Wiki post:
http://en.wikipedia.org/wiki/Australian ... _Territory

Some of you may not have read this article:
http://spaceinfo.com.au/antarctica20090902.html

Now obviously it is a harsher climate than Hawaii, Chile, or the Canary Islands, but not as harsh or remote as space. Setting up and servicing a scope may be done at a fraction of the cost of launching one into space, especially a part of space where we have no current service capability.

There have been some ridiculous replies to this thread, including one that said the scope would collapse under its own weight here on Earth. Here is a clue: it was or is being built here on Earth, so if it won't collapse during the build process it is unlikely to spontaneously collapse when finished. Actually, it is built to withstand a launch with multiple G forces so it just isn't that delicate. Now during launch it will be packed up a bit, then will have to self-deploy on station. That process has always proved tricky (read about Skylab), so having a few folks around might make it easier. Others have pointed out that the JWST doesn't have a mount. Well, they build mounts for much larger instruments, so this is obviously not an insurmountable problem.

There have also been criticism over my not caring about the number of the Lagrangian points, just the location. Well, truthfully, when I speak about an iron object I don't look up the atomic number, nor do I insist on an isotopic ratio analysis. Maybe you are really disappointed in my laziness. I can live with that. Maybe I am disappointed that so few of you seem to know that Antarctica is somewhat 'partitioned' and most of you didn't read the story about this great astronomy site. I am sure you can live with that, so no harm, no foul.

As a final addition to the lack of research many of you have displayed, this particular site is virtually above the troposphere, unlike all of the other sites that are closer to the equator. Also, due to the ozone holes over the poles and the lack of air routes over the Antarctic, this is considered the best place on the planet to do IR work. It is even better than SOFIA because the air rushing past the viewing port does cause disruption in perfect seeing.

Knowing that the Hubble is ageing I am very concerned over this next great space observatory. I'd rather see it mounted anywhere than find out that all of the money we have currently spent on the JWST will end up going for naught.

BTW, I am still waiting for the link to the test plan and completed FMEA. NASA PowerPoint presentations indicate that both documents are required. I don't live in Missouri but have driven through it four times so I will remain skeptical until I can download the files.

 

[michaelmozina]

Hi --
Some of you seem to be confused and think this scope should be placed in the 'outback'. Please read this Wiki post:
http://en.wikipedia.org/wiki/Australian ... _Territory

I didn't mean to offend you Bill, I was simply noting that "testing" the equipment (which everyone agrees is important) doesn't necessarily mean moving that equipment thousands of miles out of the way.

I just don't believe that it needs to be an either/or proposition. It seems to me that satellites in space have served us well, just as ground based equipment has served us well. There is room IMO for both types of research, and I have great faith in the value of satellite technology. If you're going to build a ground based telescope in such a hostile environment, that will also require a long term investment and a lot of planning in choosing/building the right type of gear for the job, just like the planning and now construction that is going into this project.

By the way, welcome to the board Bill. As you can see, it can get "testy" at times here, but hey, it can be fun too.

 

[michaelmozina]

For my own case, I am not saying that we should not be taking whatever chances it will take to do this. What I am saying however, is that NASA needs to be very, very careful to make sure this works perfectly the first time it is deployed!

Just as a single ship human mission to Mars must also be perfect. There will be NO Apollo 13 type of rescue for a crew that is tens of millions of miles from the Earth!

For either type of mission, there will be absolutely NO margin for error!

And that IS the TRUTH!!!!

Space travel has always been a highly unforgiving business. It seems to me that if HST taught us anything it is that we should never take testing for granted, and perseverance pays huge dividends.

 

[MeteorWayne]

Hi --
Some of you seem to be confused and think this scope should be placed in the 'outback'. Please read this Wiki post:
http://en.wikipedia.org/wiki/Australian ... _Territory

Some of you may not have read this article:
http://spaceinfo.com.au/antarctica20090902.html

There have been some ridiculous replies to this thread, including one that said the scope would collapse under its own weight here on Earth. Here is a clue: it was or is being built here on Earth, so if it won't collapse during the build process it is unlikely to spontaneously collapse when finished. Actually, it is built to withstand a launch with multiple G forces so it just isn't that delicate. Now during launch it will be packed up a bit, then will have to self-deploy on station. That process has always proved tricky (read about Skylab), so having a few folks around might make it easier. Others have pointed out that the JWST doesn't have a mount. Well, they build mounts for much larger instruments, so this is obviously not an insurmountable problem.

.[/quote]

What is silly is that you suggest the scope can be tested in Antarcita. That IS actually silly. The scope can ONLY be deployed in 0g/microgravity. It is NOT designed to be deployed or tested on earth. Sorry, but them's the facts!!!

It will be launched in a protected configuration where the stresses of launch are planned for.

It will be deployed in the environment it is designed for.

Sheesh!!!

 

[job1207]

Ok great, we are going to look back to the beginning of time, When we were the size of a . (or smaller)

Question 1.

If "we" were there, at 13.7 billion years ago, then where were "we" at 12 Billion years ago, and so on? ( we HAD to be there 13.7 Billion years ago. There is no doubt about that. )

Question 2.

If we can see where "we" were 13.7 billion years ago, can "we" see where we were at other times?

Question 3

How is all of that possible???

 

[MeteorWayne]

Q1. Between there and here.

Q2. Yes.

 

[job1207]

Ok, you answered before I got a chance to write question 3.

How is all of that possible???

 

[MeteorWayne]

How is it not possible?

Of course "we" were not there 13.7 billion years ago, only energy was, no matter.

Matter formed after the big bang.

The galaxy formed some time after that.

We can see anything that happened within 13.7 billion years light time of us; we can not see beyond that.

 

[job1207]

Ok, but matter formed, and it was not in all parts of the present universe at a certain point. It was in a limited part of the universe.

That matter became the earth, eventually.

How can we track that matter, through, space? and of course, time.

 

[job1207]

Put another way, why can't we say, the matter that is now the earth was here 6 billion years ago. Look, there it is.

 

[MeteorWayne]

Beacuse the matter that became earth is all here on earth...a few nano light seconds away!

 

[Woggles]

Hi Everyone

I was read this article Northrop Grumman-Built James Webb Space Telescope Sunshield Design Achieves Significant Landmark, Marks Major Mission Progress. Link is http://money.cnn.com/news/newsfeeds/art ... 183285.htm

My question to those in the know is, if they are attaching a tennis court-sized sunshield on the telescope would it act as a solar sail?

 

[SpaceTas]

I can't say anything about the micrometeorite environment near L2. There should be some info from various moon missions,and if Hershel and Planck survive well then we will have some idea.

But I can comment on Antarctic astronomy. There are 2 really good sites; Dome A and Dome C. The median seeing at these sites is 0.3 arcsec. So often the seeing is comparable with the Hubble (with upgraded camera it get 0.085 arc sec). At 0.3 arcsec is the same for a space based wide field telescope. The good seeing in Antarctica is not at ice level but 20-30m up (60-100ft roughly). Above 30m it nearly always excellent. At ice level the seeing is mostly very poor 3 arcsec, with rare excellent spells. Because both Dome C and Dome A are at high altitude and in a very dry atmosphere the infra-red radiation gets through and can be observed. A 4m IR telescope at these sites would preform more like an 8m+ telescope on Mauna Kea Hawaii (best normal site), The other advantage is very long continuous night time with clear weather; with a low glow from the sun just below the horizon. Aurora are mostly not a problem as they occur in a circle round the magnetic pole.

European astronomers are looking at the Dome C site: http://arena.unice.fr/
also from Australia http://www.phys.unsw.edu.au/jacara/ see PILOT the proposed 2m telescope