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James Webb telescope reaches its final destination in space, million miles away

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Re: James Webb telescope reaches its final destination in space, million miles away

#171

Post by jandrese »

dharmab wrote: post #101
wongarsu wrote: post #78

Earlier quoted context omitted.

I've heard the (probably unfounded) story that the Soviets saw the Space Shuttle, couldn't figure out why the Americans would build it but figured there surely must be a good reason; so they copied it to also have whatever capability the Americans were after.

According to a book cited on the Wikipedia page on the Buran program, the Soviets looked at the shuttle's payload capacity and concluded it could be used to deploy military weapons into orbit.

Any orbital rocket can deploy weapons into orbit. The Shuttle was unique in that it could theoretically capture a satellite and return to Earth with it.

Re: James Webb telescope reaches its final destination in space, million miles away

#172

Post by spookthesunset »

echelon wrote: post #149
messe wrote: post #144

Earlier quoted context omitted.

The one that had the biggest influence on the design of the shuttle was probably the plan to launch into a polar orbit, rendezvous with a satellite, capture it, and land as it swung around for the next orbit. This require massive cross-range capability, in order to be able to glide back to a suitable landing site in the US, putting lower limits on the size of the wings.

The classified autonomous X-37 [1] has a cargo bay [2] and there are (were?) plans to scale it up to double the size to accommodate larger payloads and crewed missions [3]. [1] https://en.wikipedia.org/wiki/Boeing_X-37 [2] https://www.thedrive.com/the-war-zone/36440/this-is-our-firs... [3] http://www.spacesafetymagazine.com/aerospace-engineering/spa...

That X-37 photo in the wiki article had me go down the "payload fairing" rabbit hole. Still don't quite know what the "bubble wrap" is on the inside. I assume it is part insulation to protect from extreme heat and part, well, bubble wrap.

According to wikipedia those things cost around $6 million to manufacture and spacex was the first to ever bother retrieving them.

https://en.wikipedia.org/wiki/Payload_fairing

Re: James Webb telescope reaches its final destination in space, million miles away

#173

Post by 1125spacex »

mrtksn wrote: post #152
arcticfox wrote: post #38

Earlier quoted context omitted.

"doubled" the lower bound on what was surely an extremely conservative estimate meant to avoid a perception of failure if things didn't go perfectly. The Opportunity rover had a "90-day" expected lifetime and lived until 15 years old. It's great that Ariane performed superbly but this "doubling" calculation is pretty silly.

> The Opportunity rover had a "90-day" expected lifetime and lived until 15 years old. It's great that Ariane performed superbly but this "doubling" calculation is pretty silly. Yeah, no. JWST has a limited lifetime because of the finite fuel, that's completely different from building a machine for a purpose and the machine not falling apart at the end of the initial mission. When people say Ariane doubled the lifeti…

There's really no telling how good Ariane was here though, without a lot more information. Maybe if it was perfect it could have "tripled" the lifetime.

Using your driving analogy, this is like you getting 80mpg on a car that needs to hit 40mpg or heads will roll. Maybe everyone driving it would get 80mpg. Maybe someone driving extremely precisely would get 120mpg.

There's not enough information here to say how well Ariane did other than public comments from the engineers which were vague but positive.

Re: James Webb telescope reaches its final destination in space, million miles away

#174

Post by justin66 »

js8 wrote: post #158
justin66 wrote: post #138

Earlier quoted context omitted.

> It's a very subtle form of American exceptionalism. Oh, bullshit. NASA spends an awful lot of money and effort on promoting its projects to the English-language press. Does the ESA make a comparable amount of effort?

I am not sure where we disagree. I am talking about the (false) perception that the U.S. is the #1 among world nations. Maybe it is caused by comparatively higher marketing budget, but that doesn't ultimately matter, because the point is, the perception is still false, and ignoring Webb's predecessor contributes to it. OTOH, I think Webb is amazing, and fairly, perhaps without the marketing it wouldn't even exist bec…

> the (false) perception that the U.S. is the #1 among world nations

The #1 what? I wouldn't blame you for using some unkind phrases here, and I suspect you want to! But it's certainly not false that the U.S. does much more space exploration than any other nation, spends a lot more on it, achieves more in space, etc. None of that invalidates the work of other nations, and spaceflight and the production of scientific data seems like a very healthy form of competition (and cooperation!) between nations. If the U.S. isn't #1, I am curious how you are keeping score.

Herschel didn't just get less English-language press than American made space telescopes. It was less prominent in the public consciousness than short, much less expensive Japanese missions like Hayabusa and Hayabusa2. I doubt any of this is about American exceptionalism.

Re: James Webb telescope reaches its final destination in space, million miles away

#175

Post by willis936 »

bgirard wrote: post #167
willis936 wrote: post #162

Earlier quoted context omitted.

Earth's umbra doesn't reach L2. https://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra https://astronomy.stackexchange.com/questions/13585/does-ear...

I did some research here to understand this better: https://webb.nasa.gov/content/about/orbit.html > This [L2] orbit (which takes Webb about 6 months to complete once) keeps the telescope out of the shadows of both the Earth and Moon. >What is special about this orbit is that it lets the telescope stay in line with the Earth as it moves around the Sun. and > Webb's position out at L2 also makes it easy for us to talk…

As did I.

https://news.ycombinator.com/item?id=29859522

Re: James Webb telescope reaches its final destination in space, million miles away

#176

Post by justin66 »

willis936 wrote: post #162
justin66 wrote: post #139

Earlier quoted context omitted.

An object at L2 absolutely could avoid the sun and stay in Earth's shadow. It would be problematical for this spacecraft, which is powered by a solar array.

Earth's umbra doesn't reach L2. https://en.wikipedia.org/wiki/Umbra,_penumbra_and_antumbra https://astronomy.stackexchange.com/questions/13585/does-ear...

Ah, that stack exchange comment is super interesting.

"If Earth would be 9% larger in diameter, but with the same mass, its umbra would end almost exactly at L2."

Re: James Webb telescope reaches its final destination in space, million miles away

#177

Post by jacquesm »

entrep wrote: post #24
mabbo wrote: post #18

Earlier quoted context omitted.

Mirror alignment was done in the days leading up to insertion, wasn't it? Afaik, all that's left is testing and cooling- the cold side is still around 63K and needs to get down to 50K (-223C).

Mirror deployment was done before insertion, moving the 18 mirrors up from their locked position by 12.5 mm. Now, 3 months of mirror alignment will follow. They will align with a reference star having to first move one mirror a little bit to identify how the mirror affects the alignment, then calculate the alignment and move the mirror. Each mirror's position can be controlled at 10 nm resolution.

It's not only position, also deformation by pulling or pushing on the center of the mirror changing it's curvature.

Re: James Webb telescope reaches its final destination in space, million miles away

#178

Post by spookthesunset »

ceejayoz wrote: post #69
samstave wrote: post #56

Earlier quoted context omitted.

May I please subscribe to the raw images of ANY space telescope... I mean * WE* /paid/ for them... I would like to access the data provided in real-time. Where can one get the raw images?

Once they're taking images, you'll have access to them. Hubble's all went up (in raw as well as processed form) at https://hla.stsci.edu/ , http://hst.esac.esa.int/ehst/ , and several other places. Expect the same for JWST. (Same for any other NASA mission. Here's the Curiosity rover: https://mars.nasa.gov/msl/multimedia/raw-images/ )

> Once they're taking images, you'll have access to them.

What you say is true but with an asterisk. They grant time limited exclusive access to the data to whatever science team is using the telescope. It's basically an embargo agreement. That way the science team gets the first chance to do their research and publish it. Not all missions fall under this and in some cases you'll see what is going on right away. Eventually all data will become public.

I'll just quote their policy[1]:

    Access to science data from most active missions is often limited to the Program Investigator Team during a period of exclusive access immediately following the observations. The duration of the exclusive access period ranges from a few months to as much as a year, depending upon the mission, the program category, and other factors. Some other data, such as those obtained during facility commissioning, or those that are found to duplicate concurrent observations by a Guaranteed Time Observer (GTO), may also be embargoed for a period of time. Data falling under exclusive access can be discovered via MAST public interfaces, but may not be retrieved except by authorized and authenticated persons. Following the expiration of the applicable exclusive access period, science data become available for public use without restriction.
There is a ton more [2] about how to apply to get time on the telescope. Dudes even have a standalone desktop application to help put together the proposal.

    [1] https://archive.stsci.edu/publishing/data-use
    [2] https://jwst-docs.stsci.edu/jwst-opportunities-and-policies

Re: James Webb telescope reaches its final destination in space, million miles away

#179

Post by adolph »

messe wrote: post #144
tobylane wrote: post #93

Earlier quoted context omitted.

What was the intended mission? I’ve read about the classified missions that went ahead, iirc one of them did use the full capacity.

The one that had the biggest influence on the design of the shuttle was probably the plan to launch into a polar orbit, rendezvous with a satellite, capture it, and land as it swung around for the next orbit. This require massive cross-range capability, in order to be able to glide back to a suitable landing site in the US, putting lower limits on the size of the wings.

Scott Manley has a wonderful explainer on it "The Most Important Space Shuttle Mission Never Happened":

https://www.youtube.com/watch?v=_q2i0eu35aY

Re: James Webb telescope reaches its final destination in space, million miles away

#180

Post by spookthesunset »

js8 wrote: post #158
justin66 wrote: post #138

Earlier quoted context omitted.

> It's a very subtle form of American exceptionalism. Oh, bullshit. NASA spends an awful lot of money and effort on promoting its projects to the English-language press. Does the ESA make a comparable amount of effort?

I am not sure where we disagree. I am talking about the (false) perception that the U.S. is the #1 among world nations. Maybe it is caused by comparatively higher marketing budget, but that doesn't ultimately matter, because the point is, the perception is still false, and ignoring Webb's predecessor contributes to it. OTOH, I think Webb is amazing, and fairly, perhaps without the marketing it wouldn't even exist bec…

> OTOH, I think Webb is amazing, and fairly, perhaps without the marketing it wouldn't even exist because of all the American deficit hawks.

It's just like everything else in life. You can build the best product in the world but it won't make a damn bit of impact on people's lives unless you let them know it exists. Marketing your product is just as important to its success as the product itself.

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