James Webb Space Telescope

[Tom]

In four days, all going well, the James Webb Space Telescope will launch on the extremely reliable Ariane 5 vehicle. It will take about 30 days to travel 1.5M km to a distant, stable orbit around the Sun. And while it's doing all that, it'll slowly unfold itself in a process that has many potential points of failure, before hopefully showing us imagery from the very edge of the observable universe, objects that existed only 100-250 million years after the Big Bang.

Because it operates in infra red, and because it has a much, much larger mirror than Hubble (which is about 30 years old now), it should be as big a step up from Hubble as Hubble was from ground-based telescopes. Objects 100 times fainter than what Hubble can see will be visible. Detail levels will be a good 10 times greater. It'll be able to detect planets orbiting distant stars. And distant objects in our own Solar System.


View: https://www.youtube.com/watch?v=RzGLKQ7_KZQ


Fingers crossed. It'll be a few months before it begins operation (it takes a while to cool down and to set everything up). I can't wait.

 

[Tom]

Due to bad weather, launch now planned for 25th.

Webb: new target launch date

www.esa.int

Fuck watching Digby the Biggest Dog in the World, or some other bollocks, watch this in the afternoon instead. 12:20–12:52 GMT.

 

[Lamp]

Really looking forward to see the images it produces

 

[Tom]

10 billion dollars in the payload section at the top of that rocket.

 

[Gwadien]

10 billion dollars in the payload section at the top of that rocket.

View attachment 45452

We're spending 10x that on a railway.

 

[Zarjazz]

10 billion dollars in the payload section at the top of that rocket.

View attachment 45452

That could be one very expensive xmas fireworks show if things go wrong. Those scientists involved in its construction must be bricking it right about now.

 

[Gwadien]

I wonder if it's insured.

 

[Tom]

It's an Ariane 5, only one of those has failed and it was the very first one in the 1990s. Due to incorrect software implementation IIRC.

 

[Tom]

View: https://www.youtube.com/watch?v=21X5lGlDOfg

 

[Deebs]

Watching now, so excited!

 

[caLLous]

Oh fuck me, I missed it. Set an alarm and everything.

 

[Scouse]

Good shout @Tom

 

[Tom]

And off she goes

 

[DaGaffer]

And off she goes View attachment 45469

How long does it take to travel the million miles to its orbit?

 

[Tom]

About a month.

 

[Deebs]

Was amazing to watch, had goosebumps and felt quite emotional watching it. Hope everything else goes ok and once fully setup we see some amazing pictures and great discoveries.

 

[old.Osy]

Where Is Webb? NASA/Webb

During Webb's launch, deployment and commissioning, 'WhereIsWebb' tracked Webb's 'flight' to L2 orbit, its state and progress during its deployment and commissioning process, and finally the release of its first images. This process is now complete. During this process, the page constantly...

jwst.nasa.gov

 

[Tom]

View: https://twitter.com/NASAWebb/status/1475138567454265352?s=20

 

[Tom]

View: https://twitter.com/NASAWebb/status/1476194840018890756

 

[Tom]

Bit nerve-wracking. The sunshield covers are the purple things you can see in this animation, they protect the shield when stowed away. The shield can't be pulled out and tensioned if they don't retract.


View: https://twitter.com/NASAWebb/status/1477074540081692680


Interesting to think that a lot of this is due to the need to get it into the payload section of an Ariane 5. If Starship becomes fully operational and reliable, its payload capacity is way, way bigger, and this level of complexity wouldn't be required.

 

[Gwadien]

Bit nerve-wracking. The sunshield covers are the purple things you can see in this animation, they protect the shield when stowed away. The shield can't be pulled out and tensioned if they don't retract.


View: https://twitter.com/NASAWebb/status/1477074540081692680


Interesting to think that a lot of this is due to the need to get it into the payload section of an Ariane 5. If Starship becomes fully operational and reliable, its payload capacity is way, way bigger, and this level of complexity wouldn't be required.

Is there any reason why they couldn't deploy all this shit closer to earth so if it goes tits up somebody could go up and fix it like they did a number of times on the Hubble?

 

[Tom]

Yes, it is designed to observe at the L2 Lagrange point, which is a gravitationally stable-ish place that's nice and quiet. It will require regular corrections (using the telescope's own fuel) to keep it in the same position in the sky, but the Ariane rocket did such a good job that it's using less fuel now to reach it's position, so the mission has been extended by many years. The Sun, Earth and Moon will all be "behind" the telescope's sunshield, so it can look at the Universe without picking up Talk Radio and other rubbish.

It's a bit like going into the middle of nowhere, well away from light pollution, to gaze at the Milky Way at night.

The shield is fully out now, although the layers aren't yet separated:


View: https://twitter.com/NASAWebb/status/1477124649465040897

 

[Tom]

Anyway I have my own suspicion that SpaceX might come up with a plan to send a couple of Starships over there in the future, perhaps to refuel and repair it. Who knows. Or maybe it'll be much cheaper by then to just bung some more telescopes up using Starship's massive payload space.

 

[DaGaffer]

Is there any reason why they couldn't deploy all this shit closer to earth so if it goes tits up somebody could go up and fix it like they did a number of times on the Hubble?

Lagrange points are cool.

 

[Zarjazz]

Yes, it is designed to observe at the L2 Lagrange point, which is a gravitationally stable-ish place that's nice and quiet.

The scientific reason is that placing something in a geosynchronous orbit around the L2 point is that in that location the Earth is always eclipsing the Sun, hence blocking the telescope from most of the sun's light. The telescope requires extreme cold to work and even hiding behind the Earth it still requires the sun shield. The L2 point is also still close enough to the Earth to allow high bit-rate transmissions.

 

[Tom]

The scientific reason is that placing something in a geosynchronous orbit around the L2 point is that in that location the Earth is always eclipsing the Sun, hence blocking the telescope from most of the sun's light. The telescope requires extreme cold to work and even hiding behind the Earth it still requires the sun shield. The L2 point is also still close enough to the Earth to allow high bit-rate transmissions.

That isn't true. The telescope is in a halo orbit at L2, which means it'll always see sunlight. The sunscreen that can see sunlight will be hot enough to boil water. The sunscreen nearest the mirror will be at almost 0 Kelvin.

Besides which, at that distance the Earth isn't nearly big enough to eclipse the Sun.


View: https://www.youtube.com/watch?v=524fcGyki5c

 

[Gwadien]

Can't other orbits fuck with it that far out? Or is that why it's life is shorter than Hubbell because it's going to have to make adjustments?

 

[Scouse]

Can't other orbits fuck with it that far out? Or is that why it's life is shorter than Hubbell because it's going to have to make adjustments?

A million miles is fuck all really.

 

[Gwadien]

It's past the moon though.

 

[Tom]

Can't other orbits fuck with it that far out? Or is that why it's life is shorter than Hubbell because it's going to have to make adjustments?

Other orbits are fucking with it, that's why it's going there now. It's a point of gravitational equilibrium, where the combined gravitational pull of the Sun, Earth and Moon let it remain in the same position in the sky, relative to us. If it were closer to us, it'd fall back to Earth. So you'd have to put it in Earth orbit, which would then mean constant corrections to keep it facing away from the Sun. And then, for a lot of the time it'd be looking at the Earth, which would be useless. If it were further away, it'd escape into the Solar System. But where it's going now, it'll just sit there and require only minor corrections now and again to keep it in place.

If it helps, think of it as orbiting the Sun, but being pulled along a bit faster by the Earth+Moon. One other benefit is that where it is, there's going to be very little that can hit it. Micrometeorites will be extremely unlikely to find it, because they'll all be in the Earth's gravity well already - the telescope is right on the edge, well outside the danger zone.

It'll only last as long as it has fuel. It does have the ability to be refuelled, but so far there are no plans to do that. Which is why I suspect someone might try and do it at some point.