James Webb Telescope

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Of coarse we don't know certainty, but saw one scientist say in ten years may have ways to reach, refuel, and other upgrades to extend JWT life span.

There is also talk of sending up pieces and building a telescope in space.

It took couple decades to get JWT to this point. Unlike Hubble it can be focused in space. Like a kid in a candy store, think images will be spectacular.
yeah 24 day to fall off local maxima, but should have fuel to stay at L2 waiting for fix or NASA could decide to let it wobble off to recover later.
A little off topic from knives, but cool none the less.
 
Actually, the opposite is true. On its current trajectory, the telescope won't get there without doing another burn. The problem is that the telescope cannot slow down because doing so would require it to turn around, thereby exposing the cold side of the telescope to the sun.

Currently, Webb is moving too slowly to get there and the final burn will accelerate the telescope just enough for it to reach L2.

James Webb Space Telescope notches crucial maneuver to set its path
Right, but presumably the amount of underthrust was minimized so to use as little fuel as possible for the final burn. I'm ready to switch to feet/second or meters/second.
 
It's scary since Hubble took a shuttle mission to fix it (optics, etc) and several later missions to resupply it. JW is so far out, it is unlikely there is the political will to mount a mission to fix or resupply it for 5 or 10 years.

They designed the telescope acknowledging they had 'one shot'. For example, each of the mirrors can calibrate themselves so that they focus the light correctly. The Hubble mistake wont be repeated! But that introduces a bit of a contradiction.... although that flexibility makes it more robust to misalignment error (something that is highly likely for telescope origami), the added complexity also adds more points of failure. That makes it quite exciting to watch it come online!

But you are right... if there is catastrophic failure, it will be unable to fulfil its mission goals. They will not send out a crew to fix it. As for lifespan? I have heard some scientists talk about sending out robots to refuel the telescope. This might even be a bit too 'scifi'... but it is more likely than a manned mission. It would be interesting to find out if 'dead-simple' refueling was built into the design to help facilitate the possibility of an autonomous refueling mission.
 
So, it has slowed to 261 meters/ sec. I get that it's slowing due to mostly the sun's gravity, but I'm having trouble understanding what will complete the slowing as it moves close to the L2 position. Isn't L2 essentially zero gravity?
 
So, it has slowed to 261 meters/ sec. I get that it's slowing due to mostly the sun's gravity, but I'm having trouble understanding what will complete the slowing as it moves close to the L2 position. Isn't L2 essentially zero gravity?

I don't really know the answer to this...

L2 is only quasi-stable. Solar radiation and interplanetary dust are enough perturbations (over a long period) to knock the spacecraft out of these stable points. Fortunately the decay is slow. But JWST isnt going to park on L2... it is going to orbit around it! This orbit is known as a Halo orbit. I believe they are doing this so that the solar panels will always be exposed to sunlight (if JWST just parked in L2, the earth would eclipse the sun).

Since station keeping is required, fuel has been budgeted to do regular corrections. I imagine they will use these thrusters to do any final maneuvering into the L2 Halo orbit... I could be wrong...
 
It was enlightening to me to understand that the instability of L2 was actually desirable, because the stable LaGrange positions tend to collect stuff. I think that you are correct that the orbit is to stay out of the earths shadow.

It's difficult for me to imagine moving into L2 without any negative thrust. Maybe they have a way to do this without introducing heat to the cold side.
 
It's difficult for me to imagine moving into L2 without any negative thrust.

Your question was interesting so I read a little bit more! I am not going to pretend I know the answer. But this NASA post has a big clue:

the Ariane 5 launch insertion was intentionally designed to leave some velocity in the anti-Sun direction to be provided by the payload. MCC-1a similarly was executed to take out most, but not all, of the total required correction (to be sure that this burn also would not overshoot). In the same way, MCC-1b, scheduled for 2.5 days after launch, and MCC-2, scheduled for about 29 days after launch (but neither time-critical), and the station-keeping burns throughout the mission lifetime will always thrust just enough to leave us a little bit shy of the crest. We want Sisyphus to keep rolling this rock up the gentle slope near the top of the hill – we never want it to roll over the crest and get away from him. The Webb team’s job, guided by the Flight Dynamics Facility at NASA Goddard, is to make sure it doesn’t.

Since getting to L2 is like rolling a ball up a hill, rather cleverly, it looks like they designed the trajectories to only almost get to the top of the hill. Like you mentioned earlier... the sun's gravity is slowing the spacecraft down. Without the thrusters, JWST would not quite reach L2. So they dont need negative thrust! Gravity is doing that job for them. They only need thrust to keep nudging it away from the sun.

I guess a lot of the final positioning will be done during the halo orbit insertion burn. But now you have got me thinking.... what if there is some major miscalculation and JWST overshoots! They are operating on the assumption that it does not. But it can't provide negative thrust... it will roll down the far side of L2!!! These space agencies are clever... I am sure they have thought about this. Although they won't be expecting it to happen, I bet they have some emergency protocol. Complete speculation from here: perhaps they are just forced to reorient the spacecraft so that they can thrust back towards the sun. The cost of such a maneuver (other than fuel) might be another forced cooling period.
 
JWST is (& will continue to be) very very interesting now that that science will begin but for those who haven't looked 'toward the sun' this mission (link) is one of my personal fav's .... the "polar opposite" in terms of challenges (hot vs cold) ... originally called the Solar Probe Plus it was re-named after the mathematician whose amazing work it hopes to better understand ... very cool given that the probe was renamed in his honor while still alive (1st time that has happened I believe). JHU/APL did an amazing job with this mission & continues to do so ...

https://www.nasa.gov/content/goddard/parker-solar-probe
Still healthy after 10 orbits ...
 
JWST is (& will continue to be) very very interesting now that that science will begin but for those who haven't looked 'toward the sun' this mission (link) is one of my personal fav's .... the "polar opposite" in terms of challenges (hot vs cold) ... originally called the Solar Probe Plus it was re-named after the mathematician whose amazing work it hopes to better understand ... very cool given that the probe was renamed in his honor while still alive (1st time that has happened I believe). JHU/APL did an amazing job with this mission & continues to do so ...

https://www.nasa.gov/content/goddard/parker-solar-probe
Still healthy after 10 orbits ...
Cool I mean 🔥 As said we are in golden age of Astronomy. 3.8 million miles from surface has a shield to keep it from getting fried. It's the only star we can study up close helps to understand others in vast universe.
 
Yeah Keith - for me one of the coolest things for me was the TPS. Incredibly light density / carbon "foam" along with other composite (carbon-carbon) materials and some very special coatings ... cutting edge material science at work.

https://www.nasa.gov/feature/goddar...shield-installed-on-nasa-s-parker-solar-probe
https://ultramet.com/parker-solar-p...f,comparatively frosty 600 degrees Fahrenheit.

Interestingly the shield is actually "moveable" during its flight so certain instruments are given line of sight when desired and shielded when not ...
 
Webb has all kinds of camera variables to use in different types of views. Hubble changed our
perception of the Universe.

With far greater light gathering and camera capabilities we are in for some mind blowing images.
 
I'm sure the images will be stunning, but the fact that they are images translated from wavelengths that we can't see makes them a bit artificial in my mind.

In that regard I'm much more interested in the scientific understanding that will be gained. Fantastic project.
 
That doesn't bother me. We as humans have limited hearing, eyesight & smell compared to others in the animal kingdom. Wave lengths determined by our biological makeup.

We create amazing instruments like Hubble & James Webb to expand our horizons.
 
Did we have a general astronomy thread?? I couldnt find one (admittedly not a deep search).... Since this thread is active, you guys might enjoy this Hubble image of gravitational lensing:

potw2129a.jpg


[Image credit: NASA/ESA - galaxy cluster MACSJ0138.0-2155]

A bit old now... but remains as fascinating as ever!
 
Just a reminder..... there is a freaking helicopter on Mars!!!

Aerial view of Perseverance landing 'chute:

jpegPIA25217.jpg

[Source: NASA]


For Where's Wally fans, you can see the shadow of Ingenuity (the helicopter) in the bottom of the image, about 2/3rds from the left
 
Thanks for the heads up. Have YouTube on Roku stick have already targeted it. Hopefully someone will post some images here for KKF members a worthy bunch.
 
guess they are still developing the film

god forbid they lost it ;-)
 
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