JWST Countdown To Terror 😳

[ONIKKINEN]

2 minutes ago, Ags said:

As long as it doesn't go negative...

It probably will once it settles in to its orbit, but not right now hopefully. Its just gravity doing its thing and the Earth pulling JWST back as long as its "in range".

In the Sun-Earth L2 point the speed relative to the Earth becomes a meaningless statistic really since it is sort of hula-hooping around an invisible spot behind the Earth in terms the Sun-Earth line. JWST will definitely be coming towards the Earth at some point, so negative velocity.

[Captain Scarlet]

In answer to @Chaz2b … After the second main boost-thrust it’s been in free-fall, and since then the main “force” acting on it from earth’s frame of reference has been earth’s gravity decelerating it as it moves away from earth. So it’ll continually slow down until it gets to its destination.

Edited December 30, 2021 by Captain Magenta

[kirkster501]

It takes six days to do the first half of the journey to L2 and 23 days to do the other half. This is due to it slowing down as it fights against the earth, sun and moon’s gravity. It will arrive at L2 not much faster than you could drive your car. It has no ability to slow down so the speed must never be so high that it overshoots L2 or the mission is blown. Fortunately the Ariane upper stage placed it so accurately that everything is going great in that department.

The biggest test is to come, unfurling the Sun shield 😳. Fingers crossed for the next few days!

[kirkster501]

8 hours ago, Laurieast said:

I keep trying this and Stellarium crashes everytime, there is even a report about it at https://gitmemory.cn/repo/Stellarium/stellarium/activity?page=7

What am I doing wrong? 🤔 

Using TLE's from https://celestrak.com/NORAD/elements/tle-new.txt

Not sure what you are doing wrong Laurie. Just enter the RA and Dec from JPL Horizons and enter into Stellarium or CDC and it will take you right there. You can then, after doing an initial sync or blind solve get your imaging software to take you right to JWST.  In my image earlier I was a few minutes of arc off of getting JWST dead centre in the field.

[kirkster501]

Sunshield covers released. The big stuff starts now 😳

https://blogs.nasa.gov/webb/2021/12/30/webb-team-releases-sunshield-covers/

Edited December 30, 2021 by kirkster501

[JOC]

I don't know if I would want to work on something like this, you must need the patience of a saint to work at NASA/ESA considering the time it takes to do everything.  Launching the rocket (which must be the fun bit) only takes moments, but when you are looking at days to do other other stuff and even longer to send communications to and from distant satellites and space craft it must all get rather tedious.

Edited December 31, 2021 by JOC

[Ags]

@JOC We are very different people - I would find absolutely any part of the project more enjoyable than the launch and deployment phase.

[Ags]

In the video of JWST's separation from Ariane, there were quite lot of speckles drifting through the view. I wonder how clean the mirrors are now? All that clean room effort seems a bit wasted when separation took place in a snow globe?

We've discussed micrometeorites and the sunshield, but what about micrimeteorites and the primary and secondary mirrors? I believe there is a large telescope with a bullet hole in it (in the USA of course).

Edited December 31, 2021 by Ags

[Mr Spock]

12 minutes ago, Ags said:

We are very different people - I would find absolutely any part of the project more enjoyable than the launch and deployment phase.

Same here. I'd love working on this instead of doing the job I do!

[Laurieast]

10 hours ago, kirkster501 said:

Just enter the RA and Dec from JPL Horizons and enter into Stellarium or CDC and it will take you right there.

Penny dropped overnight! Got it now.

I was trying to do it with the TLE updates from https://github.com/Stellarium/stellarium/files/7777407/tle-new.txt apparently something to with "if e can become >1 something will break" 

[JOC]

On 29/12/2021 at 14:09, kirkster501 said:

This is the current location and will drift to the east a few minutes of arc per day over the next ten days.  Would dearly loved to have imaged it but there is no chance with the weather - as per usual with anything remote exciting happening in the world of astronomy in the UK.

So is this something, esp. once the solar shield is unfurled, that we are going to be to 'see; with our own eyes with our 'back-yard' telescopes?  If so, it might be worth taking a look at if skies clear.  If so once where it needs to be will it as static in the sky in terms of apparent movement or will it appear to race across the sky like the ISS?

[Chaz2b]

11 hours ago, kirkster501 said:

It takes six days to do the first half of the journey to L2 and 23 days to do the other half. This is due to it slowing down as it fights against the earth, sun and moon’s gravity. It will arrive at L2 not much faster than you could drive your car.
Really? Have you seen the speed a certain Tesla is travelling at?! 🤣

 

[kirkster501]

29 minutes ago, Mr Spock said:

Same here. I'd love working on this instead of doing the job I do!

Me too. It is unbelievably fascinating. I’m an engineer by profession and this type of thing is incredible. “You can’t achieve great heights without taking great risks” a wise man once said.

[kirkster501]

4 minutes ago, JOC said:

So is this something, esp. once the solar shield is unfurled, that we are going to be to 'see; with our own eyes with our 'back-yard' telescopes?  If so, it might be worth taking a look at if skies clear.  If so once where it needs to be will it as static in the sky in terms of apparent movement or will it appear to race across the sky like the ISS?

Yes, the halo orbit is tens of thousands of kilometres wide and we will see the sun lit side of the sunshield. So it should be possible to image it from the ephemeris coordinates.   It will be in the plane of the ecliptic.

[Ags]

38 minutes ago, Ags said:

We've discussed micrometeorites and the sunshield, but what about micrimeteorites and the primary and secondary mirrors? I believe there is a large telescope with a bullet hole in it (in the USA of course).

Found it. Here is some space telescope micrometeorite testing from the 1970s (thankfully no-one was injured):

https://astroanecdotes.com/2015/03/26/the-mcdonald-gun-shooting-incident/

[kirkster501]

The sunshield has multiple welded seams to confine a tear to the part that was penetrated by the meteorite. The mirrors can take a reasonable amount of pitting without unduly effecting the performance. Just like a mirror in my dob, the thing can be filthy and it doesn’t stop observations. 
 

There are a lot of engineering articles online about the JWST that I’ve read. People get excited about the hardware but the JWST software (scope and ground side) comprises a third of the total development costs. People don’t realise that.

[JOC]

8 minutes ago, kirkster501 said:

It is unbelievably fascinating. I’m an engineer by profession and this type of thing is incredible.

Don't get me wrong, it's not that I don't appreciate the sheer wonder of what has been constructed and what is happening, but the patience involved in these endeavours must be huge.  It's a bit like we'll launch satellite X and in 15 years we'll get photos of Y is everything goes according to plan.   It must very frustrating to perhaps have been fully involved in the creation and launch of these items and perhaps have retired long before you see the fruits of your labour.  I don't think I'd have the patience myself.  

[tomato]

I’m amazed that if the bullets went right through they didn’t do catastrophic damage to the mirror, maybe they ricocheted off the glass without going through, a 2.7m mirror will be quite thick.

I encountered a few disgruntled employees in my career, but thankfully none of them with hand guns.

 

[Pixies]

12 minutes ago, kirkster501 said:

It will be in the plane of the ecliptic.

I guess it will be at (or closely circling) the antisolar point. So due south on the meridian at midnight.

[Ags]

2 minutes ago, tomato said:

I’m amazed that if the bullets went right through they didn’t do catastrophic damage to the mirror, maybe they ricocheted off the glass without going through

The bullets only made 2-3 cm pits in the glass. The employee tried a hammer as well, with equally little success.

Of course JWST faces "bullets" that go much faster, and I imaging the mirror is somewhat lighter.

[kirkster501]

10 minutes ago, JOC said:

Don't get me wrong, it's not that I don't appreciate the sheer wonder of what has been constructed and what is happening, but the patience involved in these endeavours must be huge.  It's a bit like we'll launch satellite X and in 15 years we'll get photos of Y is everything goes according to plan.   It must very frustrating to perhaps have been fully involved in the creation and launch of these items and perhaps have retired long before you see the fruits of your labour.  I don't think I'd have the patience myself.  

Yep indeed, patience in testing, improving and testing again and again to seek out shortcomings and find out what could go wrong preemptively.  They would have done this literally thousands of times before launch.  I am quite confident the HW will work - it's the software where any issues, if present, will reside, IMO.  It is aerospace software that would have had untold billions of Monte Carlo simulations thrown at it so it should be good.  Time will tell.

I see you are a STEM ambassador.  Me too (computers and telecoms)  

[Gfamily]

The mirrors have individual actuators that'll be used as part of the initial collimation,  and i assume they'll also be able to re align any mirror element that gets knocked out of position in an impact. 

What would be interesting is if they can move a very damaged element enough to make sure it was not sending any light to the focal plane

Edited December 31, 2021 by Gfamily

[saac]

Not sure if this has been posted or not  - our last view of the JWST

Jim

https://www.bbc.co.uk/news/science-environment-59831870

[DaveS]

The inner solar system is not a good place for big telescopes due to the light pollution from the Zodiacal Light, yep even HST suffers from LP. Plus, of course, the attendant micro-meteorites.

Once we get spacecraft and engines that are better than our current stone-age dugout canoes then the place to put a big (100m+) telescope is out in the Kuiper belt.

[Ags]

What magnitude will JWST be when it is at L2?