James Webb Space Telescope

[Centex]

Perhaps some others here are as fascinated as I am by the incredible Webb Space Telescope undertaking. Some links for info just FYI:

https://www.nasa.gov/mission_pages/webb/main/index.html - NASA 'home page' for the project

https://blogs.nasa.gov/webb/ - a regularly updated NASA Blog about the real-time status of the project

https://webb.nasa.gov/ - NASA Webb launch and commissioning website, includes the "Where Is Webb?" page

https://www.nasa.gov/nasalive - the NASA Live Stream webpage which includes occasional streams relating to the Webb project

I understand that there are other sources via social media for those who use such.

Personally, I find this undertaking fascinating and inspiring for a number of reasons, among them:

• The sheer technical complexity and ingenuity involved (dare I say, "engineering audacity"?)
• The multi-national collaborative aspect - proof positive that at least in some realms of pursuit the global community can work together to achieve great things of benefit to all in spite of geopolitical differences
• The impressive diversity of individuals making this all happen - proof positive that a person's gender, race, sexual orientation, etc, etc, etc has nothing to do with their ability to make positive, meaningful, and very significant contributions in whatever professional endeavor they are motivated to pursue

The project's successes to date are impressive, IMO, and the 'excitement' continues in real-time as I post this, the deployment and commissioning still underway with lots of challenges remaining. So far the deeply talented team has been able to address the minor issues that have arisen and keep everything on track (or better) - I wish them every continued success in their bold endeavor.

[LRCURTIS]

+1 to your well written post.

Having worked for a multi-national company I was fortunate to work with a wide range of individuals from countries on six continents. It can be humbling to engage in a global, multi-cultural environment with an open mind. The realization that other countries are capable of educating and socially developing their populace in a manner equal to (or in several cases better than) America can be unsettling to many. I am looking forward to digesting the results of the JWST program. Anticipating this will be similar to the analog to digital television conversion, comparing the JWST to the Hubble telescope - waiting to be amazed.

[Vermilye]

I've been following the amazing adventure.

I do have one question - I understand the use of the L2 location to save maneuvering fuel, but wouldn't the L2 null location gather dust, etc & what effect will it have on the telescope?

[Centex]

Great question, Jon, (and it seems a plausible notion to me FWTW).

Of course I don't know the answer, I must trust that whatever the effects, the folks on the team have anticipated those and factored that into the mission. EDIT - see post #6 below

As you well know, the minutiae considered in the design and operation of Webb is absolutely mind-boggling.

FLASH - I'm following the sunshield tensioning live-stream as I type - they have just announced successful completion of the sunshield tensioning - a HUGE milestone, another incredibly complex and high-risk step accomplished!

EDIT - Sunshield Successfully Deploys on NASA’s Next Flagship Telescope (NASA Press Release)

[alanmalk]

Originally Posted by Vermilye

I've been following the amazing adventure.

I do have one question - I understand the use of the L2 location to save maneuvering fuel, but wouldn't the L2 null location gather dust, etc & what effect will it have on the telescope?

A bit I learned this morning from the live updates: An additional advantage to L2 position is that it puts the Earth between the telescope and the Sun for additional cooling.


And another tidbit that I heard: Infrared can penetrate dust much better than visible light.

[Centex]

There's so much info about the 'whys and wherefores' of the project that one can spend hours upon hours learning all sorts of nifty stuff (BTDT, and continuing, lol!)

Here, for example, a page that discusses the second Lagrange point (L2) and why it is the selected location for Webb: https://jwst.nasa.gov/content/about/orbit.html

Reviewing that page again I see this, which may go to the point of Jon's previous question:

"Some Technical Details: It is easy for an object (like a spacecraft) at one of these five points to stay in place relative to the other two bodies (e.g., the Sun and the Earth). In fact, L4 and L5 are stable in that objects there will orbit L4 and L5 with no assistance. Some small asteroids are known to be orbiting the Sun-Earth L4 and L5 points. However, L1, L2, and L3 are metastable so objects around these points slowly drift away into their own orbits around the Sun unless they maintain their positions, for example by using small periodic rocket thrust. This is why L1, L2, and L3 don't "collect" objects like L4 and L5 do."

[heavyD]

Originally Posted by Centex

Great question, Jon, (and it seems a plausible notion to me FWTW).

Of course I don't know the answer, I must trust that whatever the effects, the folks on the team have anticipated those and factored that into the mission.

As you well know, the minutiae considered in the design and operation of Webb is absolutely mind-boggling.

FLASH - I'm following the sunshield tensioning live-stream as I type - they have just announced successful completion of the sunshield tensioning - a HUGE milestone, another incredibly complex and high-risk step accomplished!

[Vermilye]

Originally Posted by Centex

There's so much info about the 'whys and wherefores' of the project that one can spend hours upon hours learning all sorts of nifty stuff (BTDT, and continuing, lol!)

Here, for example, a page that discusses the second Lagrange point (L2) and why it is the selected location for Webb: https://jwst.nasa.gov/content/about/orbit.html

Reviewing that page again I see this, which may go to the point of Jon's previous question:

"Some Technical Details: It is easy for an object (like a spacecraft) at one of these five points to stay in place relative to the other two bodies (e.g., the Sun and the Earth). In fact, L4 and L5 are stable in that objects there will orbit L4 and L5 with no assistance. Some small asteroids are known to be orbiting the Sun-Earth L4 and L5 points. However, L1, L2, and L3 are metastable so objects around these points slowly drift away into their own orbits around the Sun unless they maintain their positions, for example by using small periodic rocket thrust. This is why L1, L2, and L3 don't "collect" objects like L4 and L5 do."

Good answer. I didn't read far enough...

[WillyB]

Remember way back when Hubble took its first deep field view and we were all amazed by the number of galaxies in a completely empty section of space?

Just imagine what we'll see next!

[Mike Lewis]

In the 1930s an optical survey was undertaken of cislunar space, the area around the moon's orbit. Nothing was found. In the 1950s the survey was repeated using radar. IIRC small boulders, "junk" were found in the L4 and/or L5 positions of the earth-moon system, i.e. the moon's orbit, analogous to the Trojan asteroids that are located in the L4 and L5 positions in Jupiter's orbit around the sun. NASA just launched a spacecraft to check out the Trojans, btw.

[HABBERDABBER]

In cost, complexity and impact, I'm guessing this will rival the moon shot, accomplished over 50 years ago.
We'll see the 1st light of the Universe.
Splendid!

[John in Santa Cruz]

two very useful links. first, the NASA Blog on Webb, which gets detailed updates often a couple times a day,
https://blogs.nasa.gov/webb/

and second, the "Where is Webb" tracker which gets a short version blog entry as each major milestone is achieved, plus gives emulated realtime statistics for distance, speed, etc, has a timeline for the deployment steps
https://webb.nasa.gov/content/webbLa...ereIsWebb.html

so coming up next, tomorrow they deploy the secondary mirror 'spider' out in front of the main mirror, then they deploy the two 'wings' on the main mirror. once thats done, over the following 10 or 11 days, they exercise the mirror segment actuators, who's function is to collimate the 18 segments of the main mirror into perfect alignment. once that is done, it will be nearly time for the final orbital burn that puts JWST in its final 100,000km orbit around the L2 point.

-amateur stargazer, follows this stuff avidly

[Brian B-P]

Originally Posted by HABBERDABBER

In cost, complexity and impact, I'm guessing this will rival the moon shot, accomplished over 50 years ago.

The cost of the James Webb Space Telescope program is less than half of the Apollo program... in actual dollars. Inflation adjusted, it's about 4% of Apollo. Still huge...

[Centex]

The JWST project continues the tradition of providing 'spinoffs' - applications for innovations developed by the space program which provide benefits in the here-and-now on earth. One example specific to the JWST: Telescope Innovations Improve Speed, Accuracy of Eye Surgery.
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Deployment of the JWST Secondary Mirror is scheduled (always subject to change) to begin this morning. Links of potential interest for those following:

A good background resource about the mirror system

Deplyment Explorer - scroll to "Secondary Mirror Deployment Begins" for info on the step planned for this morning

NASA Livestream website - Live streaming coverage of the JWST Secondary Mirror Deployment is scheduled to begin ~10:20a.m. Eastern Standard Time today. These live-streamed events typically include narration with all sorts of fascinating info provided.
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Fans of the Hubble Space Telescope will doubtless remember the nearly catastrophic mirror aberration discovered after launch of the Hubble. In that case catastrophe was avoided when a 'fix' was developed and installed on the Hubble by a Space Shuttle crew servicing mission.

I can't help but think that the lessons learned from Hubble played at least some small part in the design of the JWST's very sophisticated provisions for individual mirror-segment alignment and 'optical tuning' even after it is positioned at L2, far beyond the reach of any servicing mission of the sort that 'saved' Hubble. The "Actuators" that make this possible are discussed in the mirror background resource link I provide above, and for the hard-core geeks this technical paper: Cryogenic Nano-Actuator for JWST.

[Dcboyd]

I am fascinated not only with the technology, but in the temperature variation between the hot and cold side. Seems to me the hot side so far, is in a medium human survival range of temperatures. I am not suggesting a human could live in a vacuum, without a suit of some sort. Just fascinating.
Guess the reason the ISS spins.

[Centex]

Originally Posted by Dcboyd

I am fascinated not only with the technology, but in the temperature variation between the hot and cold side. Seems to me the hot side so far, is in a medium human survival range of temperatures.

I've been surprised at the 'moderate' (128F and 53F as I type this) hot side temperatures.

If I'm understanding the trajectory correctly at this point the craft is not yet in the 'shadow' of the earth (as it will be at L2) so we're seeing the effect of the sun's direct radiant heat on those two sensor points? And just the 'shade' provided by the now deployed sunshield provides the radical difference on the cold side (-233F and 323F as I type this)?

Fascinating indeed, a dramatic demonstration of how harsh and 'sharp-edged' the temperature environment is in the vacuum of space; lacking any atmosphere to 'temper' things, a little shade goes a long way!

I wish I'd thought to record the temperatures from the activation of those sensors a few days ago, I'm doing that now and it'll be fun to watch those hot side temperatures as the craft continues to distance itself from the sun outside of the earth's shadow over the next ~10+ days. I'd love to see a 'plot' of those hot side temperatures over time and/or distance as the craft travels farther from the sun and finally moves into the earth's shadow, perhaps at some time NASA will provide that.
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Kudos again to the JWST team as the Secondary Mirror is now deployed and latched!

[Dcboyd]

3 days ago hot side was 80F.

[Centex]

Originally Posted by Dcboyd

3 days ago hot side was 80F.

Interesting, do you recall if that was the hotter or cooler of the two sensors?

I understand they've been altering the craft attitude as a way to manage temps for deployment-specific reasons (e.g. keep certain motors / components in desired ranges for deployment operations) so that may bear on temps at the two hot side sensors we get to see?

IOW the two reporting hot side sensors may not have consistent sun exposure over this deployment phase of the project?

[Dcboyd]

If I remember it was like 50 and 80. I was really surprised.

[Centex]

Originally Posted by Dcboyd

If I remember it was like 50 and 80. I was really surprised.

While watching the livestream yesterday there was specific mention of orienting the craft to reduce temps of sunshield tensioning motors prior to undertaking that activity - perhaps that coincided with your observation?

This whole thing of temperature management and tools the team can use for that is indeed another fascinating aspect of the undertaking. Big brains, and lots of them, at work, lol!