JWST Countdown To Terror 😳

[Zermelo]

1 minute ago, Ags said:

I would be more worried about a passing Ferengi shutle claiming salvage rights on the gold mirror!

Given that the gold layer is very thin, would the quantity of beryllium be worth more?

[markse68]

13 hours ago, kirkster501 said:

There are still a lot of moving parts to getting this thing deployed yet, despite the success so far.

The mirrors themselves have to be "unlocked" (they were locked to prevent the launch vibrations wrecking them). The unlocking moves the mirrors - the entire mirror segment -  forward by about one cm.   Do that 18 times.  But then, amazingly, they can be moved to nanometer precision with respect to each other.  How can any motor have the granularity to do that?  As an engineer myself I find that fascinating.  Even a motor focus that many of us use on our home telescopes can move the focuser to micron accuracy.  But to nanometer accuracy, in those extreme cold temperatures after surviving the stresses of launch?  It is quite incredible.

You can see why this thing cost $10billion.

Found this- quite complex- driven by stepper motors 

https://authors.library.caltech.edu/91580/1/106983S.pdf

 

[Mr Spock]

If it doesn't have any latinum, it's of no interest to the Ferengi.

[tomato]

7 hours ago, markse68 said:

Found this- quite complex- driven by stepper motors 

https://authors.library.caltech.edu/91580/1/106983S.pdf

 

Thanks for providing the link to this, there are some good old fashioned gears in the actuators! It is easier to see where the $10 billion has been spent when read articles like this, all tested at ambient then put it in the cryo chamber and do it all again.

My previous post of hoping to see this technology move into amateur scopes was maybe a tad optimistic…

 

[kirkster501]

This has to be the most complex project humanity has ever attempted.  Not the most important - of course not - but the most complex.  It is almost unfathomable the amount of pioneering technology that exists inside the JWST. To say nothing of actually building it, transporting it, launching it and getting it on the correct trajectory.  The Apollo program was a piece of cake compared to this!

[AstroKeith]

Apparently all the mirror steering mechanisms work - main segments, secondary mirror and fine steering mirror.

[Swoop1]

On 12/01/2022 at 16:33, kirkster501 said:

This has to be the most complex project humanity has ever attempted.  Not the most important - of course not - but the most complex.  It is almost unfathomable the amount of pioneering technology that exists inside the JWST. To say nothing of actually building it, transporting it, launching it and getting it on the correct trajectory.  The Apollo program was a piece of cake compared to this!

Isn't JWST 'Old' technology?

My understanding of this type of project is that there is a cut off time during development when they say "No more upgrades- we build to this spec" otherwise they would never get it finished because they keep trying to shoe horn in the latest release of widget.

[kirkster501]

25 minutes ago, Swoop1 said:

Isn't JWST 'Old' technology?

My understanding of this type of project is that there is a cut off time during development when they say "No more upgrades- we build to this spec" otherwise they would never get it finished because they keep trying to shoe horn in the latest release of widget.

Agreed, as evidenced by the fact that the sensors, by today's (2022) standards, are quite small.  There would have been a change freeze long ago.

[Mr Spock]

You might think something like a sensor could be upgraded without any changes. But, increased resolution etc comes with increased data transmission requirements, and that comes with extra power requirements, and that comes with... you can see where this is going!

If what is up there works properly, we'll have all the data we could wish for.

[AstroKeith]

Every electronic component (including sensors) will need to be radiation hardened, or at least characterised. This is one of the biggest restraints on using anything 'new'

[Ags]

Is the JWST an RC or some other design?

[ONIKKINEN]

JWST is an off-axis three mirror anastigmat: https://en.wikipedia.org/wiki/Three-mirror_anastigmat

Sounds like a star-trek word, i like it.

As far as im aware no commercially available telescope has this kind of design right now.

[Sunshine]

3 hours ago, Swoop1 said:

Isn't JWST 'Old' technology?

My understanding of this type of project is that there is a cut off time during development when they say "No more upgrades- we build to this spec" otherwise they would never get it finished because they keep trying to shoe horn in the latest release of widget.

Which is why they decided on a good old reliable Telrad for pointing! it can withstand anything and can be had for less than NASA’s lunchroom sugar packets budget for the week.

Edited January 13, 2022 by Sunshine

[Alien 13]

3 hours ago, Swoop1 said:

Isn't JWST 'Old' technology?

My understanding of this type of project is that there is a cut off time during development when they say "No more upgrades- we build to this spec" otherwise they would never get it finished because they keep trying to shoe horn in the latest release of widget.

Pretty much the same as most military projects I worked on, you start with cutting edge tech but by the time the R&D is finished and manufacturing completed it can be 10 years out of date, then you have an in-service time of up to 20 years. Thankfully things started changing when I left the industry and the need to re-invent the wheel each time has gone, often specialist companies can supply whats required off the shelf now even if it means extra testing etc.

Alan 

Edited January 13, 2022 by Alien 13

[Rusted]

10 hours ago, Alien 13 said:

Thankfully things started changing when I left the industry and the need to re-invent the wheel each time has gone,

Alan 

That reads as if your were personally responsible for holding back military progress.
 

[Alien 13]

15 minutes ago, Rusted said:

That reads as if your were personally responsible for holding back military progress.
 

It does read that way doesn't it 😃 I did push for change though and a lot of commercial products got incorporated into systems like the Panny Toughbook (must have bought hundreds of those). The biggest change was when companies like Samsung entered the game..

Alan

[kirkster501]

15 hours ago, Mr Spock said:

You might think something like a sensor could be upgraded without any changes. But, increased resolution etc comes with increased data transmission requirements, and that comes with extra power requirements, and that comes with... you can see where this is going!

If what is up there works properly, we'll have all the data we could wish for.

Many of the HST sensor's iconic images have been taken with small sensors by today's standards.   Consider the last servicing mission was in 2009 - a lifetime ago in electronics terms.   In many cases all this sensor megapixel stuff is consumer marketing.

[Rusted]

2 minutes ago, kirkster501 said:

Many of the HST sensor's iconic images have been taken with small sensors by today's standards.   Consider the last servicing mission was in 2009 - a lifetime ago in electronics terms.   In many cases all this sensor megapixel stuff is consumer marketing.

Does that mean that you can't use Remote Desktop?
Or some similar [more sophisticate]  means of controlling or upgrading the distant electronics?
 

I am sure many believe the JWST will provide pretty pictures ten times sharper than the HST. 
Since the JWST works in the infra red it has the resolution of a very expensive 8" SCT.

 

[powerlord]

It's also about 'what works' as well, and then there's the need to have radiation hardened electronics.

Military wise, I suppose it explains the fact that we have just entered the 10th year since drones (i.e. quadcopters) were made possible from a 'build it yerself' POV (that's when I built my first one too) - and yet they are not exactly everywhere in the military (wee personal ones I mean). which does seem incredible).

I want my DJI Astroscope.It takes off, flies to 10k, starts its rockets (just fill with fuel to reuse) and moves up to 150k miles above your house. It then spends freefall time targetting and imaging your chosen DSOs, before falling back down to 10k, where the rotors start again, slowing it down into a hover again by 1k, and landing back in your garden.

I don't know if you've seen the latest DJI drones with stablized telephoto lens ?

 

[gilesco]

33 minutes ago, powerlord said:

It's also about 'what works' as well, and then there's the need to have radiation hardened electronics.

Military wise, I suppose it explains the fact that we have just entered the 10th year since drones (i.e. quadcopters) were made possible from a 'build it yerself' POV (that's when I built my first one too) - and yet they are not exactly everywhere in the military (wee personal ones I mean). which does seem incredible).

I want my DJI Astroscope.It takes off, flies to 10k, starts its rockets (just fill with fuel to reuse) and moves up to 150k miles above your house. It then spends freefall time targetting and imaging your chosen DSOs, before falling back down to 10k, where the rotors start again, slowing it down into a hover again by 1k, and landing back in your garden.

I don't know if you've seen the latest DJI drones with stablized telephoto lens ?

Don't know if you recall that guy who went to that extremely high altitude in a (helium?) gas balloon and parachuted off? If I recall he went into an uncontrollable spin for much of his descent, because the air resistance was so low and his suit was so bulky he couldn't really control and stabilise himself like a parachutist would normally do. My guess is that you'd need some pretty expensive stabilising equipment to allow a DJI to acquire any faint DSO target and stop it from just spinning out of control.

Still, a nice pipe dream - with the recent weather here, that's something we need!!

[Rusted]

How long before you can rent time on telescopes in low earth orbit?

 

[Stu]

Back to JWST, and apologies if this has been posted already, but latest estimates seem to say up to twenty years fuel remains, largely due to the precision of the Ariane rocket.

https://www.space.com/james-webb-space-telescope-fuel-20-years?utm_medium=social&utm_source=facebook.com&utm_content=aas&utm_campaign=socialflow&fbclid=IwAR0NDnjaZTobNqGaYccMOfqdp4ZP53nky3lbUbv9NyBSDs6Rlb-gYOIpcEM

[Zermelo]

47 minutes ago, Stu said:

Back to JWST, and apologies if this has been posted already, but latest estimates seem to say up to twenty years fuel remains, largely due to the precision of the Ariane rocket.

https://www.space.com/james-webb-space-telescope-fuel-20-years?utm_medium=social&utm_source=facebook.com&utm_content=aas&utm_campaign=socialflow&fbclid=IwAR0NDnjaZTobNqGaYccMOfqdp4ZP53nky3lbUbv9NyBSDs6Rlb-gYOIpcEM

I follow a feed from that site, and a couple of times already I've seen that phrase: "This Lagrange point is balanced between the gravitational forces of the sun, Earth and moon ...", but in fact the JWST L2 point relates solely to the sun and earth. Yes, there are a set of Lagrange points for the earth-moon system, but they're different.

A different article from Space talks about a question I asked a few pages up, namely the initial targets and proving the optics:

https://www.space.com/james-webb-space-telescope-first-observing-targets

[Zermelo]

59 minutes ago, Stu said:

Back to JWST, and apologies if this has been posted already, but latest estimates seem to say up to twenty years fuel remains, largely due to the precision of the Ariane rocket.

https://www.space.com/james-webb-space-telescope-fuel-20-years?utm_medium=social&utm_source=facebook.com&utm_content=aas&utm_campaign=socialflow&fbclid=IwAR0NDnjaZTobNqGaYccMOfqdp4ZP53nky3lbUbv9NyBSDs6Rlb-gYOIpcEM

I think this is confirmation of the original optimism, which is great news.

We saw some great coverage from the NASA control room, showing reactions to the successful launch and deployment. Does anyone know if there was any similar coverage of ESA/Ariane engineers when it became clear how accurate the launch was? Or was it a case of people reading the round-robin email the following day?

 

[AstroKeith]

13 minutes ago, Zermelo said:

I follow a feed from that site, and a couple of times already I've seen that phrase: "This Lagrange point is balanced between the gravitational forces of the sun, Earth and moon ...", but in fact the JWST L2 point relates solely to the sun and earth. Yes, there are a set of Lagrange points for the earth-moon system, but they're different.

 

Actually, the Sun/Earth L2 is perturbed by the Moon, the force being around 1% of the balancing Sun/Earth forces. Small but when you are pointing a telescope, massive!

May be the large diameter orbit that JWST performs around L2 helps smooth the perturbation out?