4 ms·

Cool videos thanks. Do you have any handy links to why it takes 30 days to unfold everything? I assume there are good reasons, but I just can't imagine what the

Cool videos thanks. Do you have any handy links to why it takes 30 days to unfold everything? I assume there are good reasons, but I just can't imagine what they are.

spaetzleesser 5y ago
I think there is a lot of testing done after each step. It also may have to do with the cooling.
- cogman10 5y ago
  AFAIK, the equipment is super sensitive as well. They likely don't want to proceed to the next stage until they are absolutely sure the previous stage happened successfully, otherwise they'll risk damaging things which will hose the whole mission.
smarx007 5y ago
I think most critical phases you’d want to happen when the satellite is in direct contact with the ground stations (they probably make extensive use of relay satellites to maximize windows of telemetry/payload data transmission, but here we are talking about issuing critical command sequences). Those windows are not 8 hours long. Further, it apparently takes almost 30 days to travel to the L2 Lagrange point and not all systems deploy until then. Edit: nope, I was wrong, it’s going to deploy a whole range of systems while on the way to the L2. https://youtu.be/RzGLKQ7_KZQ https://youtu.be/RzGLKQ7_KZQ
gadnuk 5y ago
Here's another video expanding a bit more on that deployment sequence: https://www.youtube.com/watch?v=WY9KckPI68Y https://www.youtube.com/watch?v=WY9KckPI68Y The observatory has around 7000 moving parts with complex structures for the primary and secondary mirrors and more importantly, the sunshield that would be used to keep the observatory instruments at a specific low temperature. It will take roughly 30 days for Webb to reach the start of its orbit at L2. At the end of 30 days, the telescope should have stabilized itself in an orbit around L2. But I would assume it takes that many days for deployment and unfolding everything because of the sheer number of parts and motions involved coupled with things like getting to L2, stabilizing orbit, temperature stability and all the checks for the instruments on board along with the mirror deployment (since it's not one big sheet of mirror). Here's a link which gives an idea about the logistics involved (along with a cool video series of the journey embedded): https://hackaday.com/2021/11/02/30-days-of-terror-the-logistics-of-launching-the-james-webb-space-telescope/ https://hackaday.com/2021/11/02/30-days-of-terror-the-logist... To fathom how complex the sunshield deployment is (and that's just a part of the whole sequence), from the link above: "Full deployment of the sunshield is without a doubt the sketchiest part of the whole process. The sunshield consists of five separate metalized Kapton sheets, each the size of three tennis courts. Each one must be unrolled, extended to its full size, tightened, and spaced out vertically for the sunshield to do its job. This takes the coordinated action of 140 release mechanisms, 70 hinges, eight deployment motors, about 400 pullies, and nearly 400 meters of cable to accomplish, not to mention the sensors, wiring harnesses, and computers to control everything. It’ll take the better part of two days to complete the sunshield deployment." The whole thing is just insane. From this talk by Dr. John Mather: https://www.youtube.com/watch?v=2RLGx_wgyAw https://www.youtube.com/watch?v=2RLGx_wgyAw Around 1:47 you can see the number of people involved. 3 space agencies (ESA, NASA, CSA), over 3000 engineers and technicians and 100 scientists worldwide.
- sophacles 5y ago
  Woah - this thing is really freaking cool. Thanks for all this info - I feel equipped to go on a long "nerd out" after work today.
konschubert 5y ago
I guess every time after you unfold a thing, you want to check it behaves as expected and keeps behaving as expected before you unfold the next thing.

Cool videos thanks. Do you have any handy links to why it takes 30 days to unfold everything? I assume there are good reasons, but I just can't imagine what they are.

spaetzleesser 5y ago

I think there is a lot of testing done after each step. It also may have to do with the cooling.

cogman10 5y ago
AFAIK, the equipment is super sensitive as well. They likely don't want to proceed to the next stage until they are absolutely sure the previous stage happened successfully, otherwise they'll risk damaging things which will hose the whole mission.

smarx007 5y ago

I think most critical phases you’d want to happen when the satellite is in direct contact with the ground stations (they probably make extensive use of relay satellites to maximize windows of telemetry/payload data transmission, but here we are talking about issuing critical command sequences). Those windows are not 8 hours long. Further, it apparently takes almost 30 days to travel to the L2 Lagrange point and not all systems deploy until then. Edit: nope, I was wrong, it’s going to deploy a whole range of systems while on the way to the L2. https://youtu.be/RzGLKQ7_KZQ https://youtu.be/RzGLKQ7_KZQ

gadnuk 5y ago

Here's another video expanding a bit more on that deployment sequence: https://www.youtube.com/watch?v=WY9KckPI68Y https://www.youtube.com/watch?v=WY9KckPI68Y The observatory has around 7000 moving parts with complex structures for the primary and secondary mirrors and more importantly, the sunshield that would be used to keep the observatory instruments at a specific low temperature. It will take roughly 30 days for Webb to reach the start of its orbit at L2. At the end of 30 days, the telescope should have stabilized itself in an orbit around L2. But I would assume it takes that many days for deployment and unfolding everything because of the sheer number of parts and motions involved coupled with things like getting to L2, stabilizing orbit, temperature stability and all the checks for the instruments on board along with the mirror deployment (since it's not one big sheet of mirror). Here's a link which gives an idea about the logistics involved (along with a cool video series of the journey embedded): https://hackaday.com/2021/11/02/30-days-of-terror-the-logistics-of-launching-the-james-webb-space-telescope/ https://hackaday.com/2021/11/02/30-days-of-terror-the-logist... To fathom how complex the sunshield deployment is (and that's just a part of the whole sequence), from the link above: "Full deployment of the sunshield is without a doubt the sketchiest part of the whole process. The sunshield consists of five separate metalized Kapton sheets, each the size of three tennis courts. Each one must be unrolled, extended to its full size, tightened, and spaced out vertically for the sunshield to do its job. This takes the coordinated action of 140 release mechanisms, 70 hinges, eight deployment motors, about 400 pullies, and nearly 400 meters of cable to accomplish, not to mention the sensors, wiring harnesses, and computers to control everything. It’ll take the better part of two days to complete the sunshield deployment." The whole thing is just insane. From this talk by Dr. John Mather: https://www.youtube.com/watch?v=2RLGx_wgyAw https://www.youtube.com/watch?v=2RLGx_wgyAw Around 1:47 you can see the number of people involved. 3 space agencies (ESA, NASA, CSA), over 3000 engineers and technicians and 100 scientists worldwide.

sophacles 5y ago
Woah - this thing is really freaking cool. Thanks for all this info - I feel equipped to go on a long "nerd out" after work today.

konschubert 5y ago

I guess every time after you unfold a thing, you want to check it behaves as expected and keeps behaving as expected before you unfold the next thing.