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  James Webb Space Telescope: comments

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Author Topic:   James Webb Space Telescope: comments
Robert Pearlman
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posted 04-23-2015 04:25 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
James Webb Space Telescope: questions and comments
This thread is intended for comments and questions about the James Webb Space Telescope and the updates published under this topic.

The JWST is NASA's next orbiting observatory and the successor to the Hubble Space Telescope. A tennis court-sized telescope orbiting far beyond Earth's moon, Webb will detect infrared radiation and be capable of seeing in that wavelength as well as Hubble sees in visible light.

Blackarrow
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posted 04-23-2015 04:28 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
Several years ago, Bruce McCandless told me that the James Webb Space Telescope was going to be fitted with a grappling point on the off-chance that a future astronaut crew might visit to carry out repairs. Is that still the case?

Will the JWST have a shuttle-type grapple-point? Would it be possible to send an Orion crew to fix JWST if it breaks down? (I do realise Orion doesn't have an "arm" but designing some sort of "grapple hook" would surely be simple compared with committing to a repair flight.)

Robert Pearlman
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posted 04-23-2015 05:14 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
There are no plans for Orion (or any other vehicle, crewed or robotic) to visit JWST, and none of the telescope's instruments can be serviced on orbit.

In 2007 however, NASA announced it would add a docking ring "just in case" something truly horrific (and obvious) were to go wrong with the observatory's deployment that astronauts might be able to help fix it. But as far as I can see, the only mention of such an adapter dates back to that original news eight years ago and since then, there has been no official confirmation that the docking ring was ever added.

BetaCanum
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posted 04-24-2015 11:35 AM     Click Here to See the Profile for BetaCanum   Click Here to Email BetaCanum     Edit/Delete Message   Reply w/Quote
Probably better to save the weight and just know that you could build a jig down the road to capture it if necessary, ala Intelsat 6.

Cozmosis22
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posted 04-24-2015 12:08 PM     Click Here to See the Profile for Cozmosis22     Edit/Delete Message   Reply w/Quote
Since this observatory will be placed more than a quarter of a million miles from Earth it is highly unlikely that there will be any crewed servicing mission. Also, a robotic mission would be too expensive and probably too complicated to be feasible. The JWST must work properly once orbited or it will become space junk.

Jim Behling
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posted 04-24-2015 12:13 PM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
Its really not viable for JWST repairs to be supported by Orion. In the deployed configuration, JWST is a delicate and contamination sensitive spacecraft. Orion's RCS thrusters would greatly affect the sunshield and would deposit exhaust on the unenclosed mirrors.

Robert Pearlman
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posted 01-14-2017 11:10 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The U.S. Departments of Commerce and State have removed the James Webb Space Telescope from the U.S. Munitions List (USML), freeing it from International Traffic in Arms Regulations (ITAR), as part of a larger set of tweaks to the space export controls.
The revised rule makes several other minor changes to technologies included on export control lists. It also shifts NASA's James Webb Space Telescope from the USML to the Commerce Control List, after the State Department concluded that the space observatory "was within the scope of spacecraft and related items that did not warrant being subject to the ITAR." JWST will require an export license as it will be shipped to French Guiana in 2018 for launch on an Ariane 5.
The Commerce Control List is a less restrictive export control system administered by the Commerce Department.

Robert Pearlman
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posted 05-30-2017 07:09 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
NASA release
NASA's "Webb-cam" Captures Engineers at Work on Webb at Johnson Space Center

NASA's special "Webb-cam" kept an eye on the development of NASA's James Webb Space Telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland, since 2012. Now that Webb telescope has moved to NASA's Johnson Space Center in Houston, Texas, a special Webb camera was installed there to continue providing daily video feeds on the telescope's progress.

Space enthusiasts, who are fascinated to see how this next generation space telescope has come together and how it is being tested, are able to see the telescope's progress as it happens by watching the Webb-cam feed online.

There were two Webb-cams at NASA Goddard. Those cameras, which were mounted inside the giant cleanroom, provided still photos (refreshed every minute) of the activity inside and gave a peek at what engineers and technicians were doing to the telescope as it came together. Over the last five years, Webb-cam viewers saw some amazing images of the Webb at Goddard, such as when all 18 gold-coated mirror segments of the Webb's primary mirror were mounted on the telescope.

"The two Webb-cams we installed in Goddard's giant cleanroom have developed a huge following over the last five years," said Maggie Masetti, social media manager and web developer on the Webb telescope mission at NASA Goddard. "With millions of views every month, you can bet that if there was a camera glitch, we heard about it right away."

The new "Webb-cam" is mounted where it has a view of the cleanroom at NASA Johnson Space Center. The camera fronts the chamber where the Webb telescope will be undergoing cryogenic testing in a massive chamber called "Chamber A." Although there is no view of Webb once it is inside the chamber during the actual cryo-optical testing, there will be much activity on Webb in the cleanroom itself for several weeks before and after.

The Web camera at NASA's Johnson Space Center can be seen online here, with larger views of the cams available here.

Fra Mauro
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posted 07-12-2017 06:35 AM     Click Here to See the Profile for Fra Mauro   Click Here to Email Fra Mauro     Edit/Delete Message   Reply w/Quote
The vault-like, 40-foot diameter, 40-ton door of NASA's Johnson Space Center's historic Chamber A sealed shut on July 10, 2017, signaling the beginning of about 100 days of cryogenic testing for NASA's James Webb Space Telescope in Houston.
Any idea of the cost of this test? I'm not questioning it's necessity, just wondering about the money involved.

dom
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posted 07-12-2017 06:56 AM     Click Here to See the Profile for dom   Click Here to Email dom     Edit/Delete Message   Reply w/Quote
I think after what happened to HST, the more tests the better!

Jim Behling
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posted 07-12-2017 07:30 AM     Click Here to See the Profile for Jim Behling   Click Here to Email Jim Behling     Edit/Delete Message   Reply w/Quote
quote:
Originally posted by Fra Mauro:
Any idea of the cost of this test?
The costs of building a clean room at the entrance of the chamber would be much greater than the test itself. The cost of the test would only be for the electrical power and fluids to run the chamber, the manpower to operate the chamber and manpower to monitor JWST. One may also include the cost of transport of the telescope to and from JSC.

This test is common to all new spacecraft designs. The issue was finding one large enough to hold the telescope in the deployed configuration.

Just a note, this is just the telescope portion of JWST, the spacecraft bus and sunshield are still in manufacturing at Northrop Grumman in Redondo Beach. The spacecraft bus will go through its own thermal vac test by itself.

Robert Pearlman
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posted 08-01-2017 07:39 AM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The James Webb Space Telescope is facing a schedule conflict for its Ariane 5 launch with ESA's BepiColombo mission to Mercury that could delay the telescope's launch by several months, reports SpaceNews.
BepiColombo, unlike JWST, has a narrow launch window in order to reach Mercury. ESA officials said earlier in July that the mission's current launch window opens Oct. 5 and runs through Nov. 28. JWST does not have similar launch window restrictions...

"It's unclear if BepiColombo will be out of the way" before JWST arrives at Kourou for launch preparations, [Alan Boss, an astronomer at the Carnegie Institution and a member of the Astrophysics Advisory Committee] said. He believed JWST needed three to six months of "full access" to facilities at Kourou to prepare for launch. "You really want to have BepiColombo long gone before you move in and start taking over."

If BepiColombo sticks to its current schedule, that could mean delaying JWST by several months. "There's some concern that that October 2018 launch may actually slip into the spring of 2019," he said.

Robert Pearlman
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posted 09-28-2017 01:47 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
The launch of the James Webb Space Telescope has been delayed to Spring 2019, but not because of ESA's BepiColombo:
"The change in launch timing is not indicative of hardware or technical performance concerns," said Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington. "Rather, the integration of the various spacecraft elements is taking longer than expected."

As part of an international agreement with the ESA (European Space Agency) to provide a desired launch window one year prior to launch, NASA recently performed a routine schedule assessment to ensure launch preparedness and determined a launch schedule change was necessary. The careful analysis took into account the remaining tasks that needed to be completed, the lessons learned from unique environmental testing of the telescope and science instruments at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the current performance rates of integrating the spacecraft element.

Blackarrow
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posted 11-01-2017 06:47 PM     Click Here to See the Profile for Blackarrow     Edit/Delete Message   Reply w/Quote
I don't want to sound unduly pessimistic, but the JWST represents a huge number of astronomical eggs in one basket. Launch vehicles aren't infallible. Highly complex satellites don't always deploy successfully. What's the back-up plan for astronomy if JWST fails?

(In human terms, that's a bit like asking, "What's your back-up plan if you die?" But people do die.)

Robert Pearlman
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posted 11-01-2017 07:09 PM     Click Here to See the Profile for Robert Pearlman   Click Here to Email Robert Pearlman     Edit/Delete Message   Reply w/Quote
A launch failure, as they say in the business, would be a bad day.

There is no back-up plan for a loss of vehicle. If Webb were to be lost, it would be a significant setback for astronomy.

damnyankee36
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posted 11-15-2017 01:43 PM     Click Here to See the Profile for damnyankee36   Click Here to Email damnyankee36     Edit/Delete Message   Reply w/Quote
I have noticed in photos and diagrams that the actual telescope appears to be fixed to the shade assembly. To me this means that the telescope will be basically pointing at a right angle to the sun at all times. I'm sure there will be a little leeway in this angle; as long as sunlight does not fall on the telescope it will stay cool.

So, it seems that its range in pointing will be somewhat limited. Also, any particular window of opportunity for an observation will only happen approx. once every 180 days if the object is on the orbital plane. Probably not a big deal but it does limit what can be observed at any given point.

Am I correct in this assumption?

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