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Andy, That was my guess. Not fiddle with what works. It's clear that the 10-14 days to reconfigure was not made up by the Phys.org writer, so likely a referred statement by the Ball personnel. Further, it seemed based on expectations of conditions in space and the mirror engineering. I think the Ball engineers and NASA have that part pretty well down at this point. But at this point in the program, Ball may not be driving this Ferrari! (edit: last sentence I meant, by the time routine imaging commences) My guess is any tweaks will consume very minor movements of any involved actuators. And as you see in the PowerPoint is these motors are capable of hundreds of thousands of rotations. It seems that any such tweak would be minor and if an actuator were to fail after such, it's likely to be a rather minor effect to the overall optics at that point. Also they do have options if any one actuator fails, for certain motions. Also, outside of a catastrophic failure, their monitoring of current draw allows them to predict motor failure and time to failure. But it sounds like the operators are shooting for perfection in the performance of this optic. |
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and FWIW: this thread made me go and check my collimation on my Newtonian  I spent 15 minutes finding out that I didn't need to have bothered and have probably ended up moving the rotation alignment of my camera which I wish I hadn't done. On the positive side: with temperature changes over the past few months, my lock nuts on the primary mirror had loosened slightly, so at least I got to tighten those up. Bottom line: don't change what isn't broken.
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| For those interested, the Webb progress page now has a mirror segment deployment graphic that shows progress of each segment. A very slow process! |
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| Wow! The mirror deployment team are making great progress. 16 of the 18 primary mirrors and the secondary are fully deployed. Two mirror segments had failed secondary coils on their LVDTs (things that measure the amount of deployment) before launch and as such had to be treated separately. They are now deploying and are at -8mm from their fully deployed position. I'm guessing that they will be fully deployed in the next 48 hours and then they can start tweaking the mirrors to turn them into a single primary that acts as one mirror. |
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I heard they caught the problem during the dry run in the cryo/vacuum chamber. This was a while ago. If they had replaced them at the time it would have been a considerable delay. Clearly they were very confident on their work-around. That they are now deploying well suggests the work around is working. It would be neat to see if they have a way to show us progress on tuning. |
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Hooray! All mirror segments have now been fully deployed  Now they can move on to aligning all those segments to act as one primary mirror.
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JWST has reached L2, congratulations! The alignment will keep on going until the end of April. After the alignment finished, JWST engineers are going to focus the telescope. Waiting, waiting, waiting... |
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I thing it's silent here because everyone has held the breath  JWST detects its first target, a star named HD 84406. It is located in the constellation Ursa Major. https://twitter.com/NASAWebb/status/1487094799408762881?s=20&t=n4V8kThuFKKWB4kpacQSCA |
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| James Webb Space Telescope sees its first star using all 18 of its primary mirror segments: Digital Photography Review (dpreview.com) Clear skies Wolfgang |
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And another nice step on the long journey towards the first JWST apod: Webb Mirror Alignment Continues Successfully – James Webb Space Telescope (nasa.gov) Clear skies Wolfgang |
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Webb is in full focus, amazing how smooth this challenging project proceeds: NASA’s Webb In Full Focus, Ready for Instrument Commissioning – James Webb Space Telescope Clear skies Wolfgang |
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FYI: NASA shares test image from Webb's Fine Guidance Sensor, the deepest image of the universe ever captured: Digital Photography Review (dpreview.com) Clear skies Wolfgang |
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The list.... https://www.nasa.gov/feature/goddard/2022/nasa-shares-list-of-cosmic-targets-for-webb-telescope-s-first-images |
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I couldn't believe my eyes: The James Webb Space Telescope uses a 68GB SSD to store its incredible images & data: Digital Photography Review (dpreview.com) Sounds like a crazy design decision ... Clear skies Wolfgang |
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james webb telescope is in my opinion a great big nothing burger I think you will find that you are in the minority here. It has the potential to make some great discoveries. I suggest you go back and hide in your negative hole. |
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| Did I... did I just read basically a conspiracy theory and someone who thinks they know better than NASA? |
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james webb telescope is in my opinion a great big nothing burger- my prediction is that it will discover nothing the hubble has not already. Mostly science works in the following way: You do experiments, measurements, observations (call it whatever you like, as long as it's empirical). It answers questions but the answera raise new questions These new questions require new experiments. New experiments answer questions but further questions will come up... ad infinitum. Therefore, HST answered questions but it has limits and scienticst want to answer them and wanted to have suitable equipment --> JWST ...my prediction is that it will discover nothing the hubble has not already. Max Planck's professor once told him to not study physics since everything has been discovered already and physics just needs a few tiny pieces for the puzzle being complete. I guess I don't have to say how history continued!? However if something "new" truly is discovered, it will be a dozen years before science announces/releases any information to the public. For instance- if the big bang is actually just a mirage from a gravitational wave front. The public will not be allowed to know this for 10 years minimum- The Astronomer Royal has once opposed publishing the discovery of the big bang with the argument that it might support religious groups in their views. He couldn't stop it. The science around JWST involves so many people, the probability that everybody would shut up is virtually 0. Besides that I find your hypothesis far fetched... In addition, looking at mandkinds history until to the present moment, to you really think that any politician gives a damn how the universe came into existence (or not... or whatever) w.r.t. public opinion? its just a research funnel for unlimited funding grants. Well, it certainly permitted and permits many people to feed their families. In addition, such a project can be a drive (or better: most certainly is a drive) for technology and research: In order to X we need to develop or research Y. I keep it up to the interested reader to learn more about JWST, it's technological challenges and solutions. oh look- bird shit that cost tax payers hundreds of millions of dollars.. Because project X failed, all other projects are a failure?! That's the problem with inductive reasoning. It just needs one counterexample to be proven wrong: - Apollo, Voyager missions, the most recent Mars missions, Space Shuttle, All of those are a great success IMHO. Certainly expensive...OR maybe all total nonsense, because why do any research? CS! |
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"Webb generates about 57GB of data each day" - i personally generate 860gb of solar data in just 45 minutes, with the lowest grade commercial camera. Creating data is easy. I could secure erase my computer's drives several times a day by random data and would essentially store several TB per day. The question is if it's valuable information. (data != information). "Specifically, IEEE Spectrum notes that the JWST is transmitting data on a 25.9GHz channel at up to 28Mb/second (0.0035GB/sec). That works out to about 12.6GB per hour." That question is often raised and the answer's simple: Nobody wanted to risk communication problems. If you can play safe, you'll do it. Especially if servicing missions are impossible. I strongly recommend to read more about the process of planning and managing such an extremely complex project. Even here on Earth, we often reject the most recent fancy tech because mission critical components need to be reliable and guaranteed to work. For many outsiders, things look simple and giving "advice" is easy unless you need to solve the problem yourself. |
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| The old adage applies: do not feed the troll! |
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I feel a little bit guilty that I started this discussion. I found it puzzling that JWST gets close to fill up the SSD every day and therefore if data transmission fails for whatever reason you either lose data by overwriting it with new one or you have to wait with imaging until the next attempt to transmit data. I assume at some point the long project runtime with all of delays is responsible for such non-optimal solutions. While it doesn't look like a big deal to replace an SSD by a larger model, you're introducing additional activities like housekeeping processes and efforts for retesting every process which uses the SSD. All in all the JWST was a very challenging project and getting it to run is a significant success. As Björn pointed out science will get a lot of data not yet available. Clear skies Wolfgang |
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Hi Wolfgang,I feel a little bit guilty that I started this discussion. Absolutely unneccesary! Your question is completely valid. I found it puzzling that JWST gets close to fill up the SSD every day and therefore if data transmission fails for whatever reason you either lose data by overwriting it with new one or you have to wait with imaging until the next attempt to transmit data. These projects undergro rigorous analyses and plannings. Assuming that it has be done appropriately (mistakes are always possible), they know in advance how much data they could possibly produce during a day and what download rate to expect. There's always a non-zero chance that at some point science has to wait since the storage is full but there's usually a definition of how often this may happen and how to mitigate such a risk (e.g., SSD full may happen once every n days in average). I assume at some point the long project runtime with all of delays is responsible for such non-optimal solutions. While it doesn't look like a big deal to replace an SSD by a larger model, you're introducing additional activities like housekeeping processes and efforts for retesting every process which uses the SSD. Some space technology seems outdated to us but the reason is: everything needs to operate under much harsher conditions and for periods of time, where the average consumer would have replaced the part several times. Björn |
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I couldn't believe my eyes: The James Webb Space Telescope uses a 68GB SSD to store its incredible images & data: Digital Photography Review (dpreview.com) That doesn’t seem at all unreasonable given that the observatory is constantly transmitting data. I haven’t added it up but that might be enough to buffer data for a day or two, which seems reasonable. The ultimate challenge is to maintain a reliable 24/7 data-link. Data stored on orbit isn’t useful. I now have my remote systems set up to constantly transmit data to a dual-site, backed up NAS system, which makes the on-site 1TB SSD complete overkill. It just allows me to be very lazy about cleaning it out every so often. John |
