James Webb Space Telescope (Technical Post ONLY !)

Flyaway

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First of Two Sunshield Mid-Booms Deploys​

The Webb mission operations team has extended the first of the sunshield’s two “arms” – the port (left side) mid-boom.

The critical step of the port mid-boom deployment was scheduled to begin earlier in the day. However, the team paused work to confirm that the sunshield cover had fully rolled up as the final preparatory step before the mid-boom deployment.

Switches that should have indicated that the cover rolled up did not trigger when they were supposed to. However, secondary and tertiary sources offered confirmation that it had. Temperature data seemed to show that the sunshield cover unrolled to block sunlight from a sensor, and gyroscope sensors indicated motion consistent with the sunshield cover release devices being activated.

After analysis, mission management decided to move forward with the regularly planned deployment sequence. The deployment of the five telescoping segments of the motor-driven mid-boom began around 1:30 p.m. EST, and the arm extended smoothly until it reached full deployment at 4:49 p.m.
As Webb’s deployment steps are all human-controlled, the schedule for deployments could continue to change – as today’s activities showed. Shortly before 6:30 p.m., the team decided to proceed with deploying the starboard mid-boom tonight, and the initial steps of that deployment began at 6:31 p.m.

 

TomS

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All 107 membrane release mechanisms holding the sunshield layers have released as designed, apparently.

Also, they had the first reported problem -- the sensors that were supposed to report that the sunshield pallet covers had retracted did not work. But they were able to confirm the retraction via other methods so all is well and they were able to keep going with the mid boom deployment.

 

FighterJock

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All 107 membrane release mechanisms holding the sunshield layers have released as designed, apparently.

Also, they had the first reported problem -- the sensors that were supposed to report that the sunshield pallet covers had retracted did not work. But they were able to confirm the retraction via other methods so all is well and they were able to keep going with the mid boom deployment.


More good news about the James Webb, strange that the sensors did not work as they were supposed to. Any reasons as to why this happened?
 

Grey Havoc

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TomS

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All 107 membrane release mechanisms holding the sunshield layers have released as designed, apparently.

Also, they had the first reported problem -- the sensors that were supposed to report that the sunshield pallet covers had retracted did not work. But they were able to confirm the retraction via other methods so all is well and they were able to keep going with the mid boom deployment.


More good news about the James Webb, strange that the sensors did not work as they were supposed to. Any reasons as to why this happened?

No word. They're taking a rest day until the 2nd before they start tensioning the sheets.
 

Flyaway

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"Work on the deployment of Webb’s sunshield mid-booms went late into the night yesterday. Webb mission management decided this morning to pause deployment activities for today and allow the team to rest and prepare to begin Webb’s sunshield tensioning tomorrow, Sunday, Jan. 2. That deployment is still expected to take place over at least two days.

This will likely affect the full timeline for Webb’s deployment. The timeline will be updated as major deployments resume."
 

Flyaway

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Deployment Timeline Adjusted as Team Focuses on Observatory Operations

Taking advantage of its flexible commissioning schedule, the Webb team has decided to focus today on optimizing Webb’s power systems while learning more about how the observatory behaves in space. As a result, the Webb mission operations team has moved the beginning of sunshield tensioning activities to no earlier than tomorrow, Monday, Jan. 3. This will ensure Webb is in prime condition to begin the next major deployment step in its unfolding process.

Specifically, the team is analyzing how the power subsystem is operating now that several of the major deployments have been completed. Simultaneously, the deployments team is working to make sure motors that are key to the tensioning process are at the optimal temperatures prior to beginning that operation.

Using an approach to keep mission operations focused on as few activities as necessary at a time, mission managers have chosen to wait to resume sunshield deployment steps after better understanding the details of how Webb is functioning in its new environment.

“Nothing we can learn from simulations on the ground is as good as analyzing the observatory when it’s up and running,” said Bill Ochs, Webb project manager, based at NASA’s Goddard Space Flight Center. “Now is the time to take the opportunity to learn everything we can about its baseline operations. Then we will take the next steps.”

Webb’s deployment was designed so that the team could pause deployments if necessary. In this case, Ochs said, they are relying on that flexibility in order to properly address how the massive and complex observatory is responding to the environment of space.

“We’ve spent 20 years on the ground with Webb, designing, developing, and testing,” said Mike Menzel, of NASA’s Goddard Space Flight Center, Webb’s lead systems engineer. “We’ve had a week to see how the observatory actually behaves in space. It’s not uncommon to learn certain characteristics of your spacecraft once you’re in flight. That’s what we’re doing right now. So far, the major deployments we’ve executed have gone about as smoothly as we could have hoped for. But we want to take our time and understand everything we can about the observatory before moving forward.”

The timeline for deployments and NASA coverage will be updated as major deployments resume.
 

TomS

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Basically, the one-day delay seems to be down to some fairly routine adjustments -- tweaking the solar panels to improve their power output and repointing the telescope a little to cool down the motors a bit to give them plenty of operating margin. Sunshield #1 tensioning was underway when the press conference began.
 

Flyaway

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"Today, at 3:48 pm EST, the Webb team finished tensioning the first layer of the observatory’s sunshield– that is, tightening it into its final, completely taut position. "

Second and Third Layers of Sunshield Fully Tightened

The Webb team has completed tensioning for the first three layers of the observatory’s kite-shaped sunshield, 47 feet across and 70 feet long.

The first layer – pulled fully taut into its final configuration – was completed mid-afternoon.

The team began the second layer at 4:09 pm EST today, and the process took 74 minutes. The third layer began at 5:48 pm EST, and the process took 71 minutes. In all, the tensioning process from the first steps this morning until the third layer achieved tension took just over five and a half hours.

These three layers are the ones closest to the Sun. Tensioning of the final two layers is planned for tomorrow.

“The membrane tensioning phase of sunshield deployment is especially challenging because there are complex interactions between the structures, the tensioning mechanisms, the cables and the membranes,” said James Cooper, NASA’s Webb sunshield manager, based at Goddard Space Flight Center. “This was the hardest part to test on the ground, so it feels awesome to have everything go so well today. The Northrop and NASA team is doing great work, and we look forward to tensioning the remaining layers.”

Once fully deployed, the sunshield will protect the telescope from the Sun’s radiation. It will reach a maximum of approximately 383K, approximately 230 degrees F, while keeping the instruments cold at a minimum of approximately 36K or around -394 degrees F.
 

Archibald

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Banking off of the northeast winds
Sailing on a summer breeze
...
So hoist up the John B's sail
See how the mainsail sets
 

Hobbes

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Mission requirement is 5 years, expected life until fuel runs out is 10 years, it can be refueled. We'll see how much margin they built in by then.
 

TomS

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The life expectancy of this multi-billion dollar satellite is 5-10 years?

They're now saying significantly more than 10 years based on the lower than planned fuel use during the initial orbital insertion. But yes, JWST's life expectancy is limited. The vehicle basically has to live in deep space to be effective and its sensors are relatively fragile by necessity. It has to use fuel to stay pointed correctly and protect the sensors from heat. Eventually that fuel will run out. There are some hopes that they might be able to design a robotic mission to refuel JWST, but there are huge risks that such a mission would damage JWST (directly or through excess heat) so it won't be attempted until it is very nearly dead (if at all -- they may just move on to even better sensors on a different mission).
 

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I feel like almost all of NASA's projects were limited to five years, probably even Hubble when it first lifted off. Definitely all of the mars rovers were rather low balled in how long they were projected to last. I assume this is because there are so many single points of failure with no hope of maintenance for most any mission that one has to lower expectations. Then again the Voyager probes are still talking and Hubble has had its mission extended past three decades. Webb due to the fragile nature of the craft likely won't be updated or repaired; it probably is too expensive and high risk to justify the costs.
 

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The life expectancy of this multi-billion dollar satellite is 5-10 years?

They're now saying significantly more than 10 years based on the lower than planned fuel use during the initial orbital insertion. But yes, JWST's life expectancy is limited. The vehicle basically has to live in deep space to be effective and its sensors are relatively fragile by necessity. It has to use fuel to stay pointed correctly and protect the sensors from heat. Eventually that fuel will run out. There are some hopes that they might be able to design a robotic mission to refuel JWST, but there are huge risks that such a mission would damage JWST (directly or through excess heat) so it won't be attempted until it is very nearly dead (if at all -- they may just move on to even better sensors on a different mission).

I think that the next telescope Super Hubble or Hubble 2 is already being designed, in fact I have seen many designs online demonstrating the possible layout and size of the proposed successor to Hubble which will dwarf both Hubble and James Webb.
 

TomS

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I think that the next telescope Super Hubble or Hubble 2 is already being designed, in fact I have seen many designs online demonstrating the possible layout and size of the proposed successor to Hubble which will dwarf both Hubble and James Webb.


This is one of several options considered for the New Great Observatory in the latest Decadal Survey.

 

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In the future, might something the diameter of starship, or even just its booster, make a much wider diameter main mirror cheaper and easier to deploy? As in, theoretically NASA could make a solid mirror nearly 9 meters wide?
 

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In the future, might something the diameter of starship, or even just its booster, make a much wider diameter main mirror cheaper and easier to deploy? As in, theoretically NASA could make a solid mirror nearly 9 meters wide?
Potentially, the exoplanet observatory backers seem to be angling for a large monolithic mirror on SLS or Starship, but there's still going to be a bunch of things like solar panels and sun shields to deploy on any long-duration observatory. So while you may save some time, money, and hair loss without the mirror deployments it's not going to make all the troubles go away.
 

Flyaway

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In the future, might something the diameter of starship, or even just its booster, make a much wider diameter main mirror cheaper and easier to deploy? As in, theoretically NASA could make a solid mirror nearly 9 meters wide?
By the time the next great observatory is ready hopefully starship would be able to deploy it directly into something like an L2 orbit or maybe something more exotic. Though I imagine as fragile as these observatories are starship would still have distance itself once the telescope deployed. Though that mission of manned would be demanding in of itself at something like four times the distance to the moon.
 

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big monolithic mirrors tend to be heavier than segmented mirrors of the same size. It's also easier to get the correct shape with segmented mirrors. So you'll still get hexagonal tiles like JWST, you can just skip the folding frame.
 

Flyaway

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Cool down analysis for JWST via NSF:

that water band is critical and 99% defines the cooldown sequence…….

the biggest enemy of any cold detector in space is water-ice and you don’t want any (any significant amount) on the detectors because of its effect on the signal ie signal-noise.

When the satellite is launched it has a little bit of surface water contamination (not much due tho the controlled environments in the ground), but unfortunately there can be quite a lot of moisture within some of the structures, especially the composite materials used for strength and weight-saving.

So as soon as these “damp” materials hit the vacuum of space, all the moisture starts wicking and evaporating away (which is good). It behaves as an orbital body, so unless it is ejected with high velocity it will generally follow the same orbit as the satellite (which can be bad in a circular orbit, less so for L2). The worst thing that can happen is that the water vapor reaches any cold surface that is at or below that water band temperature. If it does, it freezes to the surface. This is bad news for these sort of missions because the coldest bits are usually the detectors, so the risk of water-ice collecting on the detectors has to be minimised.

To do this there is an extended “warm phase” at the start of the mission, which you can see on the plot up to about Day 32. During these 32 days dedicated heaters (or decontamination heaters) are kept on which keeps the sensitive parts above the water-ice temperature. The period is calculated, along with a “decontamination analysis”, such that sufficient embedded water is wicked/ evaporated/ dissipated into space and away from the satellite.

Around L+32 days the heaters are switched off, and the “cold bits” of the payload are allowed to start cooling below the water-ice temperature. This is a “passive cooling” phase.

At this stage, the satellite is not ready for science so the cryo-coolers used to achieve final detector temperature are not needed. These are switched on around Day 80, once everything else is passively sufficiently cooled and the satellite is close to its final operational orbit and configuration. This “active cooling” phase takes the detectors down to their operating temps in the 5-20K range. I’m not sure what MIRI CCC is on that graph, but it could be Cryo Contamination Cover or similar, so possibly MIRI has yet one more way to keep water-ice away until the last minute.
 

Flyaway

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Webb’s Specialized Heat Radiator Deployed Successfully

At about 8:48 a.m. EST, a specialized radiator assembly necessary for Webb’s science instruments to reach their required low and stable operating temperatures deployed successfully. The Aft Deployable Instrument Radiator, or ADIR, is a large, rectangular, 4 by 8-foot panel, consisting of high-purity aluminum subpanels covered in painted honeycomb cells to create an ultra-black surface. The ADIR, which swings away from the backside of the telescope like a trap door on hinges, is connected to the instruments via flexible straps made of high-purity aluminum foil. The radiator draws heat out of the instruments and dumps it overboard to the extreme cold background of deep space.

The deployment of the ADIR – a process that released a lock to allow the panel to spring into position – took about 15 minutes.

Webb’s final series of major deployments is planned to start tomorrow, Jan. 7, with the rotation into position of the first of two primary mirror wings. The second primary wing – Webb’s final major spacecraft deployment – is planned for Saturday, Jan. 8.
 

Flyaway

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January 06, 2022
MEDIA ADVISORY M22-001
NASA to Host Coverage, Briefing for Webb Telescope’s Final Unfolding

When the James Webb Space Telescope’s primary mirror wings unfold and lock into place in space, the observatory will have completed all major spacecraft deployments.

Credits: Northrop Grumman

NASA will provide live coverage and host a media briefing Saturday, Jan. 8, for the conclusion of the James Webb Space Telescope’s major spacecraft deployments.

Beginning no earlier than 9 a.m. EST, NASA will air live coverage of the final hours of Webb’s major deployments. After the live broadcast concludes, at approximately 1:30 p.m., NASA will hold a media briefing. Both the broadcast and media briefing will air live on NASA TV, the NASA app, and the agency’s website.
As the final step in the observatory’s major deployments, the Webb team plans to unfold the second of two primary mirror wings. When this step is complete, Webb will have finished its unprecedented process of unfolding in space to prepare for science operations.

To join the briefing, media must RSVP no later than two hours before the start of the call to Laura Betz at: laura.e.betz@nasa.gov. NASA’s media accreditation policy for virtual activities is available online.

Webb, an international partnership with the ESA (European Space Agency) and the Canadian Space Agency, launched Dec. 25 from Europe’s Spaceport in Kourou, French Guiana. Webb is now in the process of unfolding into its final configuration in space, a human-controlled process that provides the team with the flexibility to pause and adjust as needed.

As a result of this process, the timing of these milestones may change. NASA provides regular updates on the Webb telescope blog. The public can also follow Webb’s deployments online via a “Where is Webb?” interactive tracker and a Deployments Explorer webpage.

Once fully operational, Webb will explore every phase of cosmic history – from within the solar system to the most distant observable galaxies in the early universe, and everything in between. Webb will reveal new and unexpected discoveries and help humanity understand the origins of the universe and our place in it.
Additional Webb Resources:
•Digital media kit
•Image and video galleries
•Media interview request form
For more information about the Webb mission, visit:
-end-
Press Contacts
Alise Fisher / Natasha Pinol
Headquarters, Washington
202-358-2546 / 202-358-0930
alise.m.fisher@nasa.gov / natasha.r.pinol@nasa.gov
Laura Betz
Goddard Space Flight Center, Greenbelt, Md.
301-286-9030
laura.e.betz@nasa.gov
 

Flyaway

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First of Two Primary Mirror Wings Unfolds

Webb’s iconic primary mirror is taking its final shape. Today, the first of two primary mirror wings, or side panels, was deployed and latched successfully. Each side panel holds three primary mirror segments that were engineered to fold back to reduce Webb’s overall profile for flight.

The process of deploying the port side mirror wing began at approximately 8:36 a.m. EST. At approximately 2:11 p.m. EST, engineers confirmed that the panel was fully secured and locked into place, and the deployment was complete.

Now that the port side wing panel is locked in place, ground teams will prepare to deploy and latch the starboard (right side) panel tomorrow. Upon completion, Webb will have concluded its major deployment sequence.

 

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