Do you say this because JWST replaces Hubble? If that is your reason, you need to understand it does not. It will be exploring entirely different areas of the universe. It also will NOT return images of the kind Hubble does.


If you have another reason, please share it with us.

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<span style='font-family:Arial'><span style='font-size:8pt;line-height:100%'><span style='color:blue'>setiman
If I had a cousin, his name would be Yoda.</span></span></span>

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The Webb telescope was not designed as a "replacement" for Hubble (although that is what it is being sold as now). It was meant to supplement Hubble, not replace it. Webb is optimised for infra-red, therefore it is (will be) better suited for deep-field and ultra-deep field work that is necessary for cosmology and for the study of galactic cores and other regions where visible and ultra-violet are obscured. For visible and UV, it will not replace Hubble.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

I have to run some errands atm, so I am going to ask the question and maybe someone can answer it before I get back. Why are we not using L4 &amp; L5 in the Sun-Earth system? On the Nasa link there was a link to a page describing in greater detail the Dust Cloud that was about 10 pages long and I just don't have the time right now to read it, so does anyone know?

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Calvin: Sometimes when I'm talking, my words can't keep up with my thoughts. I wonder why we think faster than we speak.
Hobbes: Probably so we can think twice.

~Calvin &amp; Hobbes~

Basically, because they aren't useful. We use some of the Lagrangian points for special satellites, but there's nothing particularly useful about L4 and L5.

Oops, I misread your question--you were talking about Earth-Sun Lagrange points, I was talking about Earth-Moon Lagrange points. The reply more or less stands, though. The Earth-Sun L4/L5 regions aren't points--they're distorted commas. There's no real advantage to putting a satellite there--the satellite won't be particularly stable, and it's a long ways away. The other LaGrange points have been used (they aren't stable, but there are halo orbits around them that are relatively stable).

Thanks for the reply Daver. If someone in the know wouldn't mind explaining a few things, here are my initial thoughts.

After looking at the Lagrange Diagrams it seemed they (L4 &amp; L5 in the Sun-Earth system) offered 2 advantages. One being no on-board fuel/propulsion system needed as they are stable positions. (Seems my understanding of the term stable in this case was wrong.) Second the spots would be free of visual interference from the Sun, negating the need for a coronagraph(?). With the weight/space savings on the satellite better viewing/recording/data transmission systems could be used in place.

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Calvin: Sometimes when I'm talking, my words can't keep up with my thoughts. I wonder why we think faster than we speak.
Hobbes: Probably so we can think twice.

~Calvin &amp; Hobbes~

I shouldn't take too much credit--I googled for L4; I thought that one of the early solar observatories might have been parked in L4 or L5; I found the smeared stable points by accident.

I don't understand your bit about lack of interference from the sun. Certainly, getting the satellite away from the earth so it wouldn't go into eclipse every hour and a half and so the earth wouldn't block its view for 45 minutes out of every hour and a half would be a distinct advantage; that's one of the reasons why Hubble was the only observatory built to be serviced by the shuttle. For the most part, though, there's no point in going out of high earth orbit for this.

Umm. There are some downsides to putting the satellite further from the earth--HST uses magnetic torquers to desaturate its momentum gyros (how about that for a buzzword jumble?). This means that Hubble doesn't periodically pollute its near environment by firing thrusters--instead, it can react against the earth's magnetic field. This isn't nearly as effective further from the earth.

From looking at the Lagrange Earth-Sun diagram and seeing that HST in L2 needs a coronagraph it appeared to me that from L4 or L5 simply due to not being in a direct line with the sun L4/5 might result in not needing the coronagraph. (I did put a question mark in quotation marks indicating I was not sure if that was a true statement or not.) The weight/space savings here would be minimal but I was thinking more along LOS and maybe being able to use the red color spectrum as a big bonus... is that not as important as I thought it would be?

I wasn't aware that HST uses a magnetic field to adjust itself. Guess my savings on fuel and a propulsion system are pretty null.

But thank you again Daver and the rest of the BABB. I am new to the world of details in Astronomy and want to know why things are the way they are. This board has been great, one of the biggest problems I faced when taking a serious intrest in Astronomy was there is an abundance of informatoin out there and trying to dicipher it without a guiding hand would be a seemingly insurmountable task.

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Calvin: Sometimes when I'm talking, my words can't keep up with my thoughts. I wonder why we think faster than we speak.
Hobbes: Probably so we can think twice.

~Calvin &amp; Hobbes~

Canada to build key component of NASA's next giant space telescope

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It has just been announced that Canada will build a key component of the gigantic James Webb Space Telescope (JWST) to be launched by NASA in August 2011. The Canadian Space Agency (CSA) recently awarded a $5-million contract to Ottawa-based EMS Technologies' Space and Technology Group for the design of the fine guidance sensor, in partnership with COM DEV of Cambridge, Ontario. Northrup Grumman Space Technologies of Los Angeles, California, will build the JWST under NASA supervision at an estimated cost of US$1.5 billion.

Mr. Alan Haase, Senior Vice-President and General Manager of EMS Technologies' Space and Technology Group announced a short time ago: "Our instrument, the fine guidance sensor, is critical to the success of the mission. It will measure the positions of very faint stars to extremely high accuracy. This is necessary for JWST to achieve the high quality of images required by the scientific objectives," said, "We are also including a tuneable filter camera that will provide unique scientific capabilities."

"When launched in 2011, JWST will peer into the past to greater distances than ever before," says Dr. Hutchings. "With it, we will be able to observe the formation of the first stars and galaxies in the universe, close to the beginning of time," he said.

It is understood that the James Web Space Telescope will Launch in August 2011 although it has not yet been decided what launch vehicle will be used for this. The total payload mass being approx 6200 kg, including observatory, on-orbit consumables and launch vehicle adaptor.

The mission duration is expected to be 5 - 10 years. The diameter of its primary Mirror will be around 6.5 meters (21.3 ft) that will be made from the material Beryllium and will have a clear aperture of 25 m. The Mass of the primary mirror being about one-third as much as the Hubble Space Telescope at present. I also understand that the mirror will have 18 mirror segments. Its great size will give astronomers an optical resolution of ~0.1 arc-seconds, and a wavelength coverage in the region of 0.6 - 28 microns to work with. Because the James Web Space Telescope is so big it will be vulnerable to damage caused by meteoroids or even space debris, it will therfore have a huge protection shield measuring 22 m x 10 m (72 ft x 33 ft).

The $824.8 million new space telescope will be operating at a temperature of less than 50 K (-370° F) in an Earth orbit 1.5 million km from Earth at L2 Point. This location lies beyond the Earth's orbit, thus the bright Earth is never seen by JWST which will reduce problems with any stray light. B)

This is a BIG Telescope to launch into space, what launch vehical do you think should be used and why? With 6 years to go before launch, time is short to design and built a new rocket!

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Is it being designed to be transported in pieces of manageable size with final assembly being completed in orbit? If so we should use the most reliable system available. I hope we can avoid building an entirely new launch system from scratch.

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For those inclined to oppose human meddling with the structure of the universe or the composition and configuration of objects and groups of objects within the universe, consider:
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Hi Gourdhead, thanks for visiting.

It is expected to be launched in one piece by a "Medium" class, Evolved Expendable Launch Vehicle (EELV). I know that the Delta IV and Atlas V fall into this group and so does the ESA Ariane 5. It will take 3 months to get to Lagrange point 2, which is 1.5 million kilometres away from Earth. The problem is that once at this location it will be out of reach of the space shuttle so repairs cannot be carried out.

Lets hope its primary mirror is not flawed in the same way Hobbles’ mirror was in the beginning.

The launch vehical has not been chosen yet so my question remains partly unanswerd.

Best wishes and Clear Skies Gourhead

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Richard Pearson
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<span style='color:purple'>Yahoo Instant Messege ID:</span> <span style='color:blue'>richard_pearson2</span>

Thanks for a nice piece on the Canadian participation in the upcoming JWST. Concerning the protection shield, it is not inteded to protect it from meteoroids, it is simply to reflect away the sunlight, so that the instrument can maintain the low temperatures required for deep infrared work.

Since the JWST is going to be operating in an L2 Halo orbit, it will not be exposed to any man-made space debris.

Concerning the mass of the probe, and the need for a new rocket, NASA believes that it can be launched with any of the following existing rockets: Atlas V, Ariane V, Delta IV.

The actual aperture will be 6.5 meters. I don't know where you got the 25 meter figure, but the instrument will NOT be 25 meters. It will be 6.5 including all segments.

Here's a link to the JWST website:
JWST Website

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James Webb Telescope mirror building moves ahead

This may be the most technically challenging part of the mission, and one that is being closely watched: if JWST can successfully launch, deploy, and use a segmented mirror, that would open the door for many other astronomy missions to do the same.

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Work has begun on the primary mirror of the James Webb Space Telescope

LINK

I hope they test this one before launch!

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The meek will inherit the earth ... the rest of us will go to the stars.

They tested the Hubble mirror. The test equipment was faulty!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

True! a flake of paint in the wrong place I think.

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The meek will inherit the earth ... the rest of us will go to the stars.

IIRC - Im going from memory here.

The test equipment was either designed or built incorrectl (wrong curvature and/or spacing of the optical parts). Ironically, an older, less accurate test showed the flaw, but they chose to believe the newer test! :roll:

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

It was a multi use jig and the wrong spacer was installed for the test. They made the mirror perfectly to the wrong spec.

Thanks for the correction. The sad thing is, as I said earlier, an older, less accurate test showed the flaw, but they chose to believe the newer test!

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Forgive me for being out of the loop, but is this the NGST? And who was James Webb?

1 - Yes.

2 - NASA administrator through much of the 1960s. While from a political background rather than a technical one, he did push for science missions during the Apollo era. What gives him heroic status among NASA administrators to this day is that he played a key role in getting Apollo funded... In the current climate, it may yet turn out to have been a brilliant move to name a space telescope for a former NASA administrator!

I dunno, I personally was never much of a fan regarding the name seeing ast the rest of the telescopes were named after famous scientists. That and let's face it, many astro-nuts don't even know who James Webb was let alone the public so from a PR perspective they could've picked a better name, IMO.

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Advancing the Webb

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Everything I need to know I learned through Googling.

For this case, I'd be willing to give them a pass because Webb was so important behind the scenes not only to funding but to keeping the budgetary axe from galling on science programs. That said, I can think of a great many people in administrative positions after whom it would be a crime to name a functioning space telescope. Assuming it's finished its asteroseismology plan B and is therefore astronomically non-functional, I hereby open a contest to suggest the most appropriate renaming of WIRE [1].

[1] (Wide-Field Infrared Explorer, main mission lost when the aperture cover failed to open properly so the cryogenic coolant all boiled away before the IR telescope could see the sky.)

Most of the obvious astronomical names have been used by earlier missions - Galileo, Copernicus (twice), Tycho (by Hipparcos), Hubble, Herschel, Planck, Cassini, Goddard (one splashed and one went to HST), Compton, Chandrasekhar, Spitzer, Kuiper, even Sagan. Eddington and Kepler are on pending missions. I wouldn't mind seeing Clyde headed to Pluto. Now Oort is still available, Tinsley would be great and one could have some fun with using Cannon and Leavitt... It's easier if the honoree has shuffled off this mortal coil, so we can hope that no one needs to name a spacecraft Phil until waaaay through the century.

I've never heard reference to this telescope as the "Hubble 2". Doesn't it have a different mission entirely?

I'm happy that they have started working on another large space telescope. Too bad it will be so many years till it is finished.

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It's sometimes referred to as the successor to Hubble, but that's a misnomer considering that it's an infrared telescope. It's more like a successor to Spitzer.

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Well put! The Webb would have been a nice complement to the Hubble...but a replacement it is not.

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Any day you wake up on "the right side of the dirt" is a good day.

T. Anderson

Could be worse. How about the "Coca Cola American Airlines Nike Space Telescope"?