First images from James Webb telescope exceed expectations
cosmosmagazine.com
cosmosmagazine.com
"The Webb telescope will use 132 small motors (called actuators) to position and occasionally adjust the optics as there are few environmental disturbances of a telescope in space. Each of the 18 primary mirror segments is controlled by 6 positional actuators with a further ROC (radius of curvature) actuator at the center to adjust curvature (7 actuators per segment), for a total of 126 primary mirror actuators, and another 6 actuators for the secondary mirror, giving a total of 132. The actuators can position the mirror with 10 nanometer (10 millionths of a millimeter) accuracy.
"The actuators are critical in maintaining the alignment of the telescope's mirrors, and are designed and manufactured by Ball Aerospace & Technologies. Each of the 132 actuators are driven by a single stepper motor, providing both fine and coarse adjustments. The actuators provide a coarse step size of 58 nanometers for larger adjustments, and a fine adjustment step size of 7 nanometers."
The actuator breaking wasn't as concerning after seeing the design.
Hmm, can you elaborate on that? What is the strong lesson for software people specifically?
Don’t get me wrong it is a beautiful design, and I’m a big fan of flexure designes in general. There is this amazing open source project which uses similar flexure mechanisms for very accurate positioning of microscope samples: https://openflexure.org/
But I fail to see any obvious takeaways which would generalise to software development. Other than perhaps “Think and work on the same problem for a decade and more and you might find a compact and elegant solution.” Which is nice, when one has that luxury.
The thing about any problem, is that "the devil is in the details." It may seem simple, from a high level, but, once we start to "drill down" into the issue, the "rough edges" appear.
At that point, we start to break out the baling wire and bubblegum, to kludge our original "graceful" design to meet the facts on the ground.
It doesn't just happen for software. Hardware suffers from the same issue, but software makes it easy to start coding before modeling the requirements and context completely.
I actually leverage this, in my own work. I call it "Evolutionary Design"[0]. It's not for the faint of heart, because a big part of it is recognizing when I'm rabbitholing, and tossing out what may be weeks of code, wholesale. I'm actually going through that process right now, with the app I'm developing. I'm working on the final feature set.
[0] https://littlegreenviper.com/miscellany/evolutionary-design-...
"There's always an easy solution to every human problem; Neat, plausible and wrong."
"The fact that I have no remedy for all the sorrows of the world is no reason for my accepting yours. It simply supports the strong probability that yours is a fake."
-- H. L. Mencken
“When the map and the terrain disagree; believe the terrain.”
-- Swiss Army Maxim
I think the actuator is an equivalent of a very clever Perl one liner.
It reminded me of a collaboration I had with a small Swiss company that did wonders with electro-discharge machining such as this flexure-based mechanism machined from a single block of aluminium: https://i.imgur.com/PDAVDmJ.jpg
Unrelated: reaction wheel assemblies (used for attitude control) typically would have one extra wheel as a "spare." Redundancy is important enough on spacecraft you expect it wherever it is practicable. I used to work in aerospace - spent enough time coding spacecraft simulation tools that I had to develop at least a working familiarity with how some of the common satellite bus systems are supposed to work :)
Doing each mirror separately would observe the photons before their wave functions are combined and so it would be the same as many small low resolution cameras instead of one big high resolution one. It defeats the purpose of a large mirror.
Before I saw the experiments in that video, I assumed photons were about as wide as their wavelength.
[1] "It's a golden oldie..."
[2] "... just to give the setup a nice high tech look and feel."
[3] "The physics behind this is pretty hefty, and not, like, youtube video material."
The laser used by the presenter has a coherence length longer than (or in the same ballpark as) the difference in optical paths in their experiement, so they get a clear interference pattern.
The Wikipedia article may explain. https://en.wikipedia.org/wiki/Coherence_length
Since you can measure coherence length (and higher-order temporal and spatial coherence statistics), it is part of the information carried by light from a luminous object that is available for imaging by a suitably designed camera.
Without phase information, you can combine different captures to improve SNR, but it won't improve the resolution. To improve resolution you need light interference, which requires phase information to be preserved.
While my example here isn't photo recognition, the same principle applies. I recently sat for a deposition where the stenographer used an "AI"transcription system. The result was literally pages of errata (vs the standard errata sheet that has space for about a dozen lines).
The consistent error I noticed was that the erroneous words were (probably) the word most expected in that position, and NOT the word that I said.
So, at a glance, it seemed like a really good transcription. In fact, many errors were barely noticeable to me and I had to go back to the audio recording to confirm. And these were errors that substantially changed the meaning, or even inverted it.
This is not merely information loss — the least surprising/lowest information item was inserted instead of the real item — this is actual information CORRUPTION.
I'd fully expect parallel phenomena from image - "AI - filling in the item most expected from the training set, and actively corrupting the data by stripping out the highest-value info bits and replacing them with the most expected.
Beware
But accurate reconstruction in the wild is just sooo far away. And for good reason - it would need to have insane amounts of experience and exposure to every bit of unusual data that existed in the world to get it right...
A engineering friend of mine was working on hardware related to mil satellite imagery, and was sent to a course that covered all the kinds of post-processing techniques they had to improve resolution and what could help those techniques upstream. He said that at the end of the course, the instructor said the bottom line was that while they could do all kinds of 'magic' to improve & enhance the photos, the best input to all their techniques that would yield the best end result, was to take a better photo in the first place.
So, yes, there really is no substitute to a good original image.
Think of the csi ‘enhance’ meme and why that is physically impossible without introducing potentially fake information.
In radio astronomy the phase information is actually collected and sometimes recorded, which is why you can have arrays of radio telescopes far apart that combine. The most extreme version of this is Very Long Baseline Interferometry (https://en.wikipedia.org/wiki/Very-long-baseline_interferome...) which was used to image the black hole at the centre of our galaxy (https://en.wikipedia.org/wiki/Event_Horizon_Telescope).
At infra-red and visible wavelengths, it is technically possible to collect some phase information, subject to noise though. So in principle it is possible to collect images including some phase at each mirror location instead of using a mirror, and then stitch them in a similar way to how it's done with radio. However, collecting the phase would be difficult and complex, especially with current technology, and likely to degrade the image so much that it's not worth doing anyway. Using mirrors is better.
In future, it is plausible that this will be done to combine images from optical telescopes far apart in space, for a very wide aparture. But it seems just as likely that they will use mirrors far apart in space, directing the incoming light to a small number of focal locations to combine the light in the optical domain first, before converting it to image data.
The full paper describing it is an excellent read:
https://www.esmats.eu/amspapers/pastpapers/pdfs/2006/warden....
I think the latter was posted to HN a few months ago.
It is their crewed program that is completely screwed by politics.
https://www.youtube.com/watch?v=VVAKFJ8VVp4
The most interesting part of the video explains why even your naked eye viewing the sky at night will cause this effect -- it's due to imperfections in the lens of your eye.
Made me laugh and learn at the same time :-)
https://phillipreeve.net/blog/best-lenses-for-sunstars/#The_...
Interestingly, some modern photography lenses have achieved aperture mechanisms with much rounder geometry, sometimes with near perfect circles at multiple apertures. This can result in a more desirable bokeh, at the cost of well defined sun stars.
https://en.wikipedia.org/wiki/Diffraction_spike
One deficiency is why apertures (effectively, the support structure in a telescope is an aperture) observe this behavior.
> No matter how fine these support rods are they diffract the incoming light from a subject star and this appears as diffraction spikes which are the Fourier transform of the support struts.
Like why is that the case?
https://en.wikipedia.org/wiki/Airy_disk
Read this if you don't immediately understand why. This is the shape of the image you see when the aperture is circular. This is the Fourier transform of a circular aperture, which, in 1D, is a sinc function.
I can't give a straightfoward answer to elucidate further, but if you've done signal processing stuff before you can probably handwavey explain that if there is a Fourier-transform relationship with one function, due to linearity and spacial invariance, you can say that it holds for all functions.
I presume that only happens if the star is far enough away, as there are plenty of images of our Sun (which is much closer) that don't look like this.
http://simbad.u-strasbg.fr/simbad/sim-id?Ident=2MASS+J175540...
Click on fullscreen icon on right-hand side, then zoom out until FoV on bottom left says about 10.63' to 12.23'.
Best I understood, that should be about the same field as the Webb image, based on the instrument definitions I read about. And I wasn't able to line up any dots visually - the new Webb image was taken with a red filter, so I thought it's likely showing photons no one's seen before.
Paging any astros for corrections.
https://twitter.com/gbrammer/status/1504369779540480002?s=21
https://www.nasa.gov/sites/default/files/thumbnails/image/te...
Spitballing.
Might there be some space/time mechanism at play whereby we're actually seeing the same handful or so of galaxies? Like maybe some lensing thing.
Or weirder, we're actually seeing right around the universe itself — as though seeing the back of your head in a mirror if you look far enough. Not a topologist, but seems a toroidal universe would have a property like this: look far enough and you see the back of your head. So perhaps the same galaxies seen from multiple angles at the same time appear to be a greater number of galaxies than there actually are.
https://en.m.wikipedia.org/wiki/Shape_of_the_universe#:~:tex....
It is not a bad thought, though. It may well do some sort of wrapping around, just at a larger scale than we can see. It's an open problem.
This might be us being in an isotropic bubble where outside of the bubble is forever gone for us to see due to expansion of universe... Not sure how CMBR falls into that however.
Per [2]:
> The actual value for critical density value is measured as ρcritical = 9.47×10−27 kg m−3. From these values, within experimental error, the universe seems to be flat.
[1] - https://en.m.wikipedia.org/wiki/Friedmann_equations#Density_...
In other words eventually the nearest galaxies will one day become the CMB as the universe continues to expand until they are on the edge, until even they fall outside the visible universe and no photons/light outside our own galaxy will be capable of reaching us and the CMB disappears.
But yes, in the distant future, it will not be possible to detect the CMB anymore (and it's entirely possible that alien civilisations that evolve at that time would probably never have a model of the Big Bang because there would be no remaining evidence of it).
I understood that the CMB is not photons from plasma but the first photons following recombination (when the universe cooled enough that electrons and protons formed first hydrogen atoms). In other words the universe was plasma just before the CMB.
I suppose though, that if space is still expanding but the universe is infinite, this might temper it out but it doesn't seem like enough - it would have to be an expansion precisely tuned to on average send radiation to 4 kelvin so we only see a cosmic microwave background, and don't wind up being bathed in an infinite amount of whatever frequency of radiation.
Infinity is funny like that.
Isn't that only true if the universe is infinitely old as well as infinitely large?
Particularly when you get into issues like entropy, which is the only real determinant of time even existing. A finite universe has a natural direction of entropy - whereas an infinite one does not, since there's an infinite amount of mass and energy and as such no possible lowest possible entropy state.
It's actually worse then that though: an infinite massed universe by definition would contain every possible configuration of that mass somewhere within it. So you and I talking right now like this, our past and future conversations would also all be somewhere else in the infinite universe happening simultaneously.
A universe with an infinite amount of mass and energy in infinite space doesn't really have any sensible notion of past, present or future - because all possible pasts, presents and future, exist at all times somewhere within it.
This is actually untrue for many reasons, but one is that there are different kinds of infinities. For instance, there are an infinite amount of real numbers between 0.0 and 1.0, and none of them are pi. Just because something is infinite, doesn't mean everything is possible within that infinity. Again, there are an infinite number of integers, but none of the are pi or 0.1 or 37.5
That was the statement, a universe with a 1kg blob of matter every billion light years would be infinite massed, but would not have all possible configurations.
It turns out #3 is wrong, so it’s still possible we live in an infinite universe.
(Imagine an infinite, unchanging universe filled with stars that magically popped into existence a billion years ago. You wouldn’t have a uniformly bright sky because even though every line of sight will theoretically terminate on a stellar surface, in most cases there hasn’t been enough time for light traveling along that line of sight — e.g. from a star 10 billion light years away — to reach your eyes.)
You are inferring infiniteness also translates somehow to cosmic density and luminosity. By definition of an infinite universe the vast majority will necessarily fall outside the observable universe and never be visible to us.
As to luminosity, even now when we look up and see dark patches in the sky, they are in fact are full of stars and galaxies. The most famous picture ever taken by the Hubble, the “Hubble Deep Field”, was taken by pointing towards a dark patch revealing 10s of thousand of galaxies. These 10s of thousands of stars and galaxies still appear as dark patches in our skies because they are not sufficiently luminous to appear in out sky as light without the aid of telescopes to collect their dim light.
You've just looped it back around: expanding space gives finite, shrinking, observable universes. Which is just exactly the Big Bang theory.
EDIT: Dark patches in the sky though don't work with infinite light sources - at the very least you have to explain why far away ones apparently switched on in a finite time in the past. But that's the issue too - we're deliberately ignoring evidence in this discussion which points away from that - i.e. the red shift which shows us galaxies are rushing away from us.
There is nothing about Big Bang theory that explains the current expansion of our Universe (i.e. dark energy). In fact the Big Bang theory predicted our Universe should have stopped expanding and began collapsing on itself due to gravity (i.e. the Big Crunch), and that’s exactly why whoever can explain why the Universe is continuing to expand has a Nobel Prize waiting.
If somehow the Universe were as you propose and wrapping around itself so we were able to stare at the back of our heads, we would only see objects from the past to a point, and then the objects would begin to appear closer in time again until the furthest point where we would once again be looking at the present.
The universe is flat as far as our best measurements go, if it is curved, it is with a much larger radius than the ~100 billion light year width of the observable universe.
It is indeed difficult to conceive but it is how it is, the universe is very big and has a whole lot of unique stuff in it.
Occasionally there is a lensing thing where we see the same galaxy twice or so, but not in any way to diminish the 10^11 other galaxies out there.
Our size as a percentage of the size of the universe is tiny, and our age as a percentage of the universe's age is still tiny. But the second number is gargantuan in comparison to the first.
And then will there simply be way less stars in the universe than there are today?
This is interesting to me because there are a lot of seemingly arbitrary ways you can try to make the size and age of the universe comprehensible, and relative to a human scale is arbitrary but at least kinda means something.
And the commenter above measured our point on a cosmic time scale by looking at where on that timeline our sun formed relative to other sunlike stars. By that metric we are kind of "in the middle." But for me the natural next question is compared to stars in general, as "sunlike stars" is maybe a bit of a texas target.
For me, in my position of refraining from associating life with particular types stars, I at least feel a bit more reassurance to think of us as in the company of stars writ large, by which measure we're not so close to the end of the cosmic span of time.
That said, I think sun-like stars is a perfectly legitimate measure to put alongside the others when casting about for intuitive ways of assessing where we stand on a cosmic timeline.
Don't worry, there are many times more galaxies in the observable universe than neurons in the human brain. Nobody can conceive of it.
The rest, as they say is history. Galaxies went from being rare things to abundant ones. Turns out the universe is teeming with them.
https://www.nationalgeographic.com/science/article/when-hubb...
There was input from galaxy researchers on such an idea, and I think it was viewed as a bit of a calculated risk compared to other normal proposals to spend the telescope time on well-known targets visible with a few hours of observing. Especially when proposals outnumber available time by a factor of approx. 7, people will question why you should gamble on something unproven. Hence "director's discretionary time".
But of course it was a smart move in setting up the field for "what's the next big thing", because if you were to find something interesting, it obviously drove the call for larger and larger telescopes to study farther and farther things. Just studying the crap out of brighter nearby things would have been relatively predictable/boring by comparison. (I exaggerate a little)
The universe would be an odd old place if that was true.
Good question. People have been wondering this and have studied whether it is possible a la periodic boundary conditions for example.
https://aapt.scitation.org/doi/abs/10.1119/1.13499?journalCo...
That strikes you as the sort of thing nobody would have noticed throughout centuries of study?
Nope. Current evidence is that space is infinite. Even if that was all wrong, then its incredibly large due to inflation and our past light cone is one tiny bit of it. As time goes on we're seeing more and more of it, and parts that used to be in contact before inflation are only just coming back into contact again (their past light cones overlapping). Those are all unique galaxies. An awful lot of physics would have to be wrong for that to not be true.
"Space, is big. Really big. You just won't believe how vastly hugely mindboggingly big it is. I mean you may think it's a long way down the road to the chemist, but that's just peanuts to space."
But that was a high-school idea, and I'm sure some clever physicists and astronomers will tell me why this isn't the case.
This image is fantastic, even though we can easily see that more work needs to be done with the alignment. It hopefully proves that alignment is all that's left.
I hope they have long life.
"The Webb telescope will use 132 small motors (called actuators) to position and occasionally adjust the optics as there are few environmental disturbances of a telescope in space."
The starburst pattern is part of the intrinsic PSF, not a signal of alignment error.
Some of the remaining misalignment is rather obvious in the higher resolution image. For example, look left of the main star and notice an "echo" of the main diffraction pattern that is not centered on a star.
Also, if you follow that pattern's downward arm to where it meets a diagonal arm of the main pattern you see a rectangular bar of increased brightness. Perhaps it indicates the need for calibrating that part of the sensor.
https://www.nasa.gov/sites/default/files/thumbnails/image/te...
HD 84406 is fairly bright, magnitude 6, eye-visible. In one of the blog posts they say it's too bright to be imaged in normal operations: https://blogs.nasa.gov/webb/2022/01/27/the-webb-team-looks-b... (You don't spend tens of billions to put a telescope into orbit just to look at HD catalog stars)
All the other sensor cruft would go away with dark-frame subtraction: https://en.wikipedia.org/wiki/Dark-frame_subtraction They're apparently not bothering with that for mirror alignment photos. Another safe bet is that a bunch of the sensor noise is because all the instruments are still warm. NIRCAM is still at 42K, and MIRI is hotter. https://www.jwst.nasa.gov/content/webbLaunch/whereIsWebb.htm... It doesn't look like they've turned on the instrument coolers yet.
It is amazing that this is done with only a single motor.
It works something like this: one direction of the motor sets which axis to align, the other direction sets the alignment of the chosen axis.
No. You misunderstood the video. There are 6 motors per mirror segment. Listen to video you linked at 9:11. It says:
“There are 6 actuators per mirror segment, and they are arranged in a hexapod or Stewart-platform configuration.”
What you are confused about is that there is only a single motor per actuator. One could naively think “oh we need a rough adjustment, and a fine adjustment so we will need two motors for each of those”. But they managed to make it more clever, and only use one motor for both the rough adjustment and the fine one. When they run the motor in one direction it adjusts the distance of the actuator roughly (minimum step size 0.058 micron) and when they run it in the other direction it adjusts finely (minimum step size is 7.7 nanometer).
If you reverse the motor, you get fine correction again until that gear turns one rotation and hits the other side of the stop, reverting to coarse correction.
Once you have things coarsely aligned, you back the motor a bit and then operate within the single rotation of that gear, staying with fine correction.
1- M60 blackhole
2- Proxima Centauri b
3- Tabby's Star
4- some apparently empty space
5- Mars surface
6- Sagittarius A*
7- Mercury's craters with water
Really curious if $10 Billion is just what it actually costs to build this incredible machine, or if the pioneering work will mean that we can do a better job making things like it now.
For perspective, $10 billion is like 1% of a single year budget in the US and I believe the estimate includes the entire lifetime operating cost of the instrument.
If it did in fact just "cost that much" I would probably "not be that bothered."
The entire astrophysics community suffered as a result of the ensuing suckout of resources. Lessons have been learned because a lot of careers were impacted.
There’s several successors to Webb on the horizon, and current thinking is to mature the technologies needed before such missions enter Phase A and is in effect committed to.
For a concrete reference on this, see the (very large) National Academies survey, which charts the course for NASA astrophysics over the next 10 years:
https://www.nationalacademies.org/our-work/decadal-survey-on...
A decent gloss on the above report is:
https://www.aip.org/fyi/2021/astro2020-decadal-survey-arrive...
which lays out the tech maturation plan under the “ Flagship mission maturation program” heading.
Compared to, oh, let’s say, $1.6 trillion dollars…
https://www.nbcnews.com/think/opinion/air-force-admits-f-35-...
But that’s just petty to point that out.
I too would like to see a debrief on “what went wrong”…if there is anything that really went wrong. I mean, there isn’t exactly an off-the-shelf solution for an infrared space telescope deployed to a phenomenally distant orbit. One might reasonably expect a few cost overruns, when you’re making mirrors that have no real precedence anywhere in human history.
I've already personally received way more value than that just following the "entertainment" of following along with the construction and launch. I would gladly pay that much again for a repeat endeavor.
Now that it looks like JWST will be able to perform actual science, I think we'll all get a lot more than $1.66/year of value out of it.
One example is comparing the final cost to the cost of the design phase. The starting point should be after the final design had been approved.
Additionally, costs need to be inflation adjusted.
I commented on this last year.
The next telescope being planned out is LUVOIR which be even bigger so they will still need to continue with folding mechanisms given the bigger size. They may need to eventually think of modular telescopes that are assembled in space.
https://en.wikipedia.org/wiki/Large_Ultraviolet_Optical_Infr...
Now if we can only get those $800MM littoral combat ships to work, we’re building like 53 of them and they don’t launch up, they launch down a few feet. Not rocket science…
JWST has a 5-year science mission requirement, with 10-year propellant life. Unfortunately it has a relatively short upper-bound on its lifetime, compared to say Hubble. Though apparently there's ~20-years of propellant onboard thanks to a precise launch, still a far cry form Hubble's 31 years and still ticking.
Should we consider 20-years a long life for such an expensive instrument?
Which probably means it would have to be a "cloud" of millions of smaller shades.
[0]https://www.northropgrumman.com/space/space-logistics-servic...
I recall a thread here when it was launched where I suggested building a twin simultaneously, and that the increment in cost was likely to be 10% of the cost of one.
One of the critics of this idea said there was no need for another, as there was only so much the JWST could discover. But it's hardly been turned on before people are trying to figure out how to make it last longer. Sigh.
P.S. I found out later that in the past NASA would build probes in pairs, and made extra parts in case one was damaged or didn't work. So it really couldn't be that expensive to have built a twin.
I can't imagine how that could come about.
> There's no way that a twin of JWST would cost only 10%.
It's kind of the way building things works. The cost of the prototype is enormous compared to the next one. For one thing, the additional R+D cost is $0. The additional cost of the software (and I bet the custom software is a big chunk) is $0. The additional cost of committee meetings to discuss competing alternatives is $0. And on and on.
When cutting parts, the cost isn't in cutting the parts. The cost is setting up the machine to cut the parts. The cutting cost is trivial.
When you're building a one-off, you aren't setting up a machine to cut the parts. You're just cutting the parts more or less by hand. It'd be too expensive to set up the machine, and calibrate, and run all of the prototypes to make sure it works, if all you need is a couple of pieces out of it.
Most components of the JWST are not within spec as they leave the factory floor; for many components, the precision required cannot be achieved with machining metrology alone. Remember that system error compounds with every new component that is incorporated. Components have to be constructed, integrated, and then measured/validated with sophisticated metrology equipment after full assembly. If you're lucky, you can modify the components you have to achieve the desired overall tolerances. But a lot of the time, you have to bin the same component a dozen times until you get a batch which happens to be correct (much like in microchip manufacturing).
And this is just for physical manufacturing -- there are multiple other dimensions which are impossible to get right the first time, requiring multiple iterations until your integration tests pass. Many of these test scenarios are extremely expensive to simulate (e.g. full-size vacuum chambers, launch and zero-g simulators), and must be done to validate every single phase of a 5-year mission to an extremely high chance of success (from transport to launch site -> launch -> full deployment -> science operations). Something as simple as a wrongly-tensioned cable is enough to scrap an entire mission -- the validation is absolutely essential to ensure that anything from a manufacturing defect to a simple human error doesn't make it through to launch.
Even in spite of all the lessons learned from JWST 1, I would be surprised if JWST 2's cost was less than 50% of JWST 1 (realistically, I'd peg it at ~80%). The testing costs are a very high fixed cost that must be paid for every unit you make. There's no other way around it.
> The testing costs are a very high fixed cost
I'm sure they are. But you won't have to design the tests and build the test rigs and validate the test procedures a second time. Secondly, you'll inevitably learn from the first test runs to need less iteration.
For example, the full-size vacuum chamber. You would already have it on hand, and not need to build another one. Having already just run #1 through it, you'd know just what to do to get #2 through.
For example, the first time I took the heads off my Mustang it took 4 hours. The second time 2 hours. The third time 20 minutes. The procedure was already all laid out for me in the shop manual. But knowing just what to do cut the time enormously.
But they did come up with a design that worked. Phew!
The cost of that special building, the building's design, the special machinery that filled it, and all those months of testing various parachute designs must have been enormous, and all count for the cost of parachute #1. The construction of parachute #2, after all that, was likely insignificant in comparison.
Namely:
These devices are one of a kind items, fabricated, integrated, and tested manually, not on some kind of assembly line. There isn’t an economy of scale.
Your conjecture is just not correct. It’s remarkably hubristic to think the people who design these space telescopes have continued to do it wrong because making duplicates has not occurred to them.
I've fabricated many things with my hands and machine tools. The second one takes dramatically less time, in every case. Even the 2nd set of materials cost less. For example, I ordered a needle bearing the other day for $7, but with shipping the total came out to $20. If I ordered two bearings, the total cost would have been $27, not $40.
It took me 20 minutes or so to install it. If I installed it a second time, I could have done it in 5 minutes.
The reason is simple. I had the right tools laid out, and I knew exactly what to do the second time.
So, yeah, I was quite unconvinced in the last thread.
P.S. I did not say they were doing it wrong.
It wouldn't surprise me if there were already more than one made for many of the bespoke components used in the telescope. Nobody makes a one-off component without some iteration and covering of their own ass in case something goes awry in shipping or assembly.
I’d suggest that it’s on you to demonstrate why these analogies should hold.
The point is they wouldn't be one of a kind if #2 was built. Planning, designing, iterative prototypes, designing tests, designing test equipment, building test equipment, devising test plans, writing the enormous amount of software require for all of that, for the ground stations, etc., all add nothing to the cost of building #2.
Normally, people take the cost of a program and divide it by the number of units built, and call that the per-unit cost. That's an accounting fiction. The first one costs the bulk, the rest cost far less per unit.
> no reason
The reason is I can't think of any endeavor where the incremental cost of #2 doesn't drop dramatically.
But what would buy us the money spent on a second telescope. One often named reason is protection against failure. That is not so straigth forward, as it sounds. If there is a random chance for failure, then a second telescope lowers the risk accordingly. However, if there is a systematic problem with the design, you would have two defective telescopes. That means, you would have even wasted more money.
Then, if both succeed, you would have increased the "bandwidth", as they could be operated in parallel. But you wouldn't have added the capability to do things differently. With Voyager 1 and 2 and Spirit and Opportunity, they at least were sent on different mission profiles and thus justified the expense.
The thing is, 10 Billion is a huge amount of money, if another JWST had cost like 5 Billions, thats a lot of scientific projects not done because of building a second space telescope. I would rather see the money spent onto different capabilities. Hubble for example is failing, we should have another telescope in the visual range ASAP. As soon as Starship reaches orbit, plans should immediately start to convert one starship into a humungeous Hubble successor.
An instrument like the Thirty Meter Telescope costs just 1 Billion. There is so much other science those 5 Billion would finance. Even if you look around only in the field of astronomy and cosmology.
I really like what they did with Curiosity/Perseverance. They used a proven platform for a second mission with updated sensor and mission profiles. So in my eyes, it would be good to invest the money not spent on a second JWST to begin construction of a true successor, which should be operational before the end of the life time of JWST. With upgraded sensors and based on anything we learn in the first years JWST is used.
This is like switching on the first electron microscope when everyone has only ever had optical microscopes. We will see new and surprising things with unprecedented fidelity. The big question has always been, "will JWST's engineering actually work?" So far, it looks like it is working very well.
W.r.t the comparison to other science and engineering efficacy, defense spending is for total shit.
Look at wasted energy inputs and unrecyclable materials as the true wastes, and the offshored/oligarch-concentrated money as a time bomb for when it gets actually deployed from its base in Virgin Islands.
I wonder if the public can really grasp it, not just grains of sands on a beach but each one a beach with 100-MILLION grains of sand.
If we can't have FTL travel in my lifetime sure would be nice if they figure out FTL communication.
So, for the James Webb, I'm sure they will be able to do the same thing to help improve and bring out details in it's images - it's just that the scale will be shifted to the red a bit.
Article: https://asd.gsfc.nasa.gov/blueshift/index.php/2016/09/13/hub...
I didn't realise there was a planet-spotting remit to JWST though. Looking forward to the results of that.
And if it's fast, how is that even possible if it's so far away?
The JWST team knows the PSF from having designed, simulated, and now actually testing the telescope, and likely it will come useful in getting the last bits of scientifically valuable information out of the data, but in normal use those diffraction spikes in particular are unlikely to be any problem. They basically only show up because the star in the test image is highly overexposed.
Now let’s mass-produce 50 of them and put them all over any Lagrange point there is, and on the dark side of the moon.
https://en.wikipedia.org/wiki/Dark_Side_of_the_Moon_(disambi...
But building an infrared telescope in one of the permanently shaded polar craters? That just might make sense at some point, but likely not we have robust crewed infrastructure in place. The polar areas are very attractive from a crewed mission perspective as well, because we now know there are sizeable amounts of water ice there and at the same time on the crater rims you can get continuous sunlight for solar panels.