Since the JWST design started, there's been a revolution in the "easiness" of launches.
I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one.
Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie.
And rather than have a fearsomely complex integrated sunshield, you could have a similar swarm of simpler satellites that provide a large cool area at L2, and then the observers just need to handle their own heat.
I suppose this could be described as microservices...in spaaaaace. Draw what parallels you will from that!
Astronomer here, we are thinking about doing interferometers in space[1,2], but it won't be a catch-all for everything. One reason is that the instrumentation is equally as important as the telescope optics itself, and it's non-trivial to have your swarm of satellites both collect light, but also do science experiments with the light. One thing we are thinking of is to fly more proto-typing missions to get the technology readiness of various components to mature stages before assembling it all together for the real thing (I would say we did not do this as well for JWST).
Is there any sense in using internet providing sattelites for astronomy? Like if starlink published it's noise data from all sattelites in realtime could it be used as one huge radiotelescope?
> Since the JWST design started, there's been a revolution in the "easiness" of launches.
Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs.
> I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one.
With space recovery and repair mission capabilities like https://nexis.gsfc.nasa.gov/osam-1.html growing, a single large asset could be easier to repair than constant refresh.
Anyways, small satellites = small sensors.
There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now.
> Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie.
Keeping a swarm of space assets ideally situated over time, with proper attitudes and control is a non-trivial problem. Look at Magnetospheric Multiscale Mission, that is considered a hard problem.
Software solutions don't always translate to hardware.
> Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs.
This is exactly the point: launch costs are coming down, and there is widespread anticipation that they will start to plummet as the next generation of launchers comes online. If/when Starship (a) becomes available + (b) has any significant competition, launch costs could plummet by an incredible factor.
Right, and the GPS constellation has been active for almost thirty years too. I think the GP is probably right that it would be great if the risk associated with a single mega launch/deployment could be spread over a fleet, but ultimately it does no good if you can't use that configuration to get the observations you want, hence the question. It has less to do with it being a "software solution" and more just whether it would actually practically work.
To their point, though, lots of ground-based radio telescopes are now also arrays of many dishes [1], so it's not at all hard to imagine that a similar configuration could be of value in space.
Well of course its not going to be simple, and I doubt it would even be possible for the JWST successor, which I assume are already being sketched out, but its an interesting idea to think about. Satellite swarms are a very active area of research, along with cheap launches enabling cheap hardware based on substantially COTS electronics, which means 10 "unreliable" things, of which 9 may fail may be cheaper than 1 gold-plated one that will definitely not fail.
And yes, they have small elements, that's the whole point. A small element is disproportionately easier to produce than a bigger one. The point of The Swarm would be to offset the small area individually small elements with a large number of them. ALMA does this, and they even pick the dishes up with giant forklifts and move them around to reconfigure the array.
Optical interferometric arrays are very hard and only recently even possible, so it's unlikely you could do it in space "soon" (even LISA is still a long way out, and that's been planned since I was at school). I obviously don't have a handle on if the added noise from positioning errors outweighs the literally astronomical baseline advantage.
And yes, Hubble might have lasted 30 years, but JWST has about 10 years life, and then it's dead and will fall away from L2 unless they can get a refuel/regas mission launched (it does have the ports for it) to it in time.
Of course any number of practical issues can torpedo such a thing from the phase space of feasible implementations, but they're still fun to think about.
> There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now.
Is there anything other than manoeuvring/orbit-correction propellant that puts an upper limit of t5he James Webbs projected life? (At least until micro meteors trash too much of the optics?) Is it possible a resupply mission capability could effectivel7y extend its useful life indefinitely? (Did they even bother putting a fuel filler on it?)
The other thing to bear in mind is the size of up coming launch vehicles. SpaceX Starship will be 9m and Blue Origin’s New Glen is expected to be 7m in diameter. Both of those could take a telescope the size of James Webb with much lest or no “unfolding” required.
Annother option with some of these cheaper launch vehicles is to build the telescope into the upper stage, using it as a bus/platform. So for example you could convert a Starship upper stage into a telescope, using its full 9m diameter for a mirror. Fully assembled on the ground before launch.
Now that the folding trick has been proven and loaded into institutional memory, I'd rather use it, e.g. LUVOIR-A at 15m in diameter, planned for the 8.4m fairing on SLS but suitable for the 9m fairing on Starship.
Instead I believe JWST will be the last telescope with reflective optics we will launch. The new thing will most likely be based on diffraction based optics (Aragoscope). It is much easier to launch in space a disc of some light and bendy material of some lightweight material than a set of hyperdelicate and precise mirrors.
According to the simulations performed in [1], an aragoscope of 1km would be able to directly image objects the size of Jupiter's moons (so basically exoplanets even on the small side) 23 light-years away.
EDIT: Took the time to scavenge the numbers: JWST has 0.1 arcseconds angular resolution, a 100m aragoscope would have a 1 milli-arcsecond angular resoulution, a 1km aragoscope 0.1 milli-arcsecond which translates to be able to alpha centauri in a 70x70 pixels patch (and so see its sunspots) or as I mentioned above exoplanets on the smaller scale at 23 light years away (Europa is 1560 km in diameter).
for that matter, how many people have seen the beginning of Half Life 1 (dated, but still one of the best intros to a game I've seen, althiough it takes a bit to get to the good part)? https://www.youtube.com/watch?v=hsTEoGoAxUk
Yes, small satellites are simpler and cheaper. Larger systems are complicated and expensive.
But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics.
At what point do we want to accept the financial tradeoffs involved? Humans and the economy also benefit from the large projects, and the management structures also teach efficiency to more people who can go on to create other exciting new sensors.
We could start with a small satellite like Sputnik, and make them grow. Eventually it will reach a point of stability with the neighbouring environment. That could be much larger than we expect. "That's no moon, it's a spaceship!"
One advantage of L2 is that it's a point of gravitational metastability when entropy inevitably hits, your satellite will slowly fall away from the point, and either depart for a long, initially slow, fall back to something rocky, or spiral out from the Earth-Moon system into interplanetary space.
An L2 swarm isn't bound together by gravity, it actually has to maintain active control to stay there, so it's a "self cleaning" area.
> But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics.
I'm going to go and assume that you used the strong force and gravity as metaphors here.
To be brutally honest, this project being fourteen years behind schedule and two thousand percent over budget damaged mine. Selling a program to taxpayers as a 500 million dollar endeavor and then extracting ten billion dollars from them is the kind of thing that should put people in prison for life.
One can reasonably argue that an over time, over budget project should be considered a failure even if it ultimately meets its objectives is a defensible comment. Arguing that people should be put in prison for such, absent actual malfeasance, is an argument that no one should ever do anything risky that's exposed to personal risk. Go away.
> this project being fourteen years behind schedule and two thousand percent over budget damaged mine.
There is a cogent response to that, as a series of questions.
1 - Which requirements changed?
2 - Which hard science & engineering problems had to be solved, and how trivial, or monumental were they?
3 - Which components failed, or passed testing, requiring rework, or re-engineering?
> Selling a program to taxpayers as a 500 million dollar endeavor and then extracting ten billion dollars from them is the kind of thing that should put people in prison for life.
Initial estimated costs were higher than 500 million. The 500 million number was an NGST estimate, right? I don't think lifecycle costs were ever estimated at 500M, it seems crazy to be that low. Are you sure you are correct on the type of costs you are providing?
14 years late, 2000% over budget even while getting a free ride from ESA -- and loudly exclaiming this thing has no redundancy whatsoever: anything at all might brick it. It may be a great telescope, but it's a miserable failure as a project.
Budget for big projects like these is not an easy concept. 14 years behind schedule means 14 more years developing the science and technology, 14 more years of research grants that probably funded project-specific but also tons of side research, new labs, new knowledge and experience that will be useful and be used way beyond the single project that funded its advancement.
Sometimes it's good to overspend if it's an excuse to fund research that would otherwise struggle to find money to stay alive.
If you’re worried about a $10b telescope, you going to lose your mind when you find out how much taxpayers overpaid on the F35 and the War in Afghanistan.
When we are talking about "directly observing a part of space and time never seen before. Gazing into the epoch when the very first stars and galaxies formed, over 13.5 billion years ago." I guess 2000% over budget seems fine to me. Even if you are thinking only about profit, I think the discoveries will pay for themself.
Plus I think the budget didn't jump from 500 million to ten billion dollars in on day, project grew and budget grew with it, and someone had to approve it, we are talking about multinational project, so I think everything is well documented and well approved from people who knows the project well better than us.
I do agree with you that if that was military budget, I would think that something is really wrong.
Why do downvoted and clearly negative comments like this nonetheless end up at the top of responses to the parent comment? Is it because it fomented a lot of responses?
On another article today, again the top response to the top comment was so negative that dang stepped in, and yet again, it's the first thing you see.
It's frustrating, because HN is doing a great job keeping things pretty constructive, but this still seems to reward negativity by thrusting it into view. Shouldn't it at least be below less-downvoted responses?
>Selling a program to taxpayers as a 500 million dollar endeavor and then extracting ten billion dollars from them is the kind of thing that should put people in prison for life.
Would you say the same about LIGO, for example? Originally thought to be easy, it turned out to be a 40 years long endeavor.
I celebrate when I see first images come out. Feels premature to now say that it is going to work. How long did it take until we noticed and understood the flaws of Hubble?
That's an overly negative comment for a project that yourself said learned from Hubble mistakes. They are exactly trying to avoid Hubble mistakes by being able to correct mirrors in absurd units, and much more. I get the idea that failure levels are so high that "everyone" get a drug shot from them. I just expected better. Hope, if you wanna call it in some way, with evidence that indicates that things are going good.
I've been thinking a lot about how much easier this could have been using orbital assembly (crewed or robotic). So, so many human years must have been spent designing and testing deployment mechanisms that simply had to function the first time.
In 2019, NASA's Astrophysics Division finished up two years assessing the feasibility of assembling a large-aperture observatory in-space. The In-Space Astronomical Telescope (iSAT) Assembly Design Study [1] concluded that In-Space Assembly (ISA) is the only option for building observatories with aperture diameters over 15 m and would still likely be strongly beneficial for smaller ones like the JWST (6.5 m aperture diameter). Efforts like Northrop Grumman’s successful Mission Extension Vehicles, the upcoming DARPA RSGS and NASA OSAM-1 missions, and the usage of Canadarm2 to install instruments with standardized interfaces on the outside of the ISS all demonstrate the increasing maturity of robotic servicing and assembly. The iSAT study describes a telescope composed of modules with standardized interfaces, launched with a spacecraft bus that has attached Canadarm2-like robotic arms that can assemble and deploy modules delivered by space tug from multiple launches. The benefits over launching monolithic spacecraft with hundreds of single points of failure (cough JWST cough) are clear: the mission won’t be limited by a single launch vehicle’s lift ability or fairing size; the same inchworming robotic arm that does initial ISA can later perform repairs and upgrades, either with freshly delivered replacement modules or by debugging malfunctioning parts (see Mars Insight); the final deployed structure doesn’t need to be designed to handle harsh launch conditions; and, design and development will be faster without needing to design and test super reliable deployment mechanisms—if a part fails during orbital checkout, launch a replacement. The primary challenge is designing hardware that today’s limited-dexterity robotics can manipulate, and figuring out supervised autonomy with fallback telerobotics for bringing humans into the loop when needed. There are definitely challenges, but this feels like the right approach. If you could do it near a crewed station for infrequent debugging EVAs, even better. After it's assembled, raise the orbit to L2 with solar electric propulsion.
> The procedure and associated hardware are verified in simulated 0-g (neutral buoyancy) assembly tests of a 14-m-diam precision reflector mockup. The test article represents a precision reflector having a reflective surface that is segmented into 37 individual panels. The panels are supported on a doubly curved tetrahedral truss consisting of 315 struts. The entire truss and seven reflector panels were assembled in 3 h and 7 min by two pressure-suited test subjects.
The difference between automated deployment mechanisms and robotic[1] orbital assembly is that we have ~60 years of experience doing the former, whereas the latter is a completely brand-new, zero-experience field.
It would be good to develop that capability, but maybe do some trial runs on assembling something a little smaller, and less critical?
[1] Human orbital assembly of the JWST is not possible, because we do not have any crewed vehicles that can make the trip.
> Human orbital assembly of the JWST is not possible, because we do not have any crewed vehicles that can make the trip.
I was assuming that GP meant "assembly in Earth orbit" and then the JWST could then rocket off on its own, fully-assembled. (Or, if they didn't mean it that way, I mean it that way.)
Assembly and testing was very difficult using humans on earth with proven techniques; it would seem impossible using novel assembly and testing technology in a novel environment.
Or conversely we'd figure out ways to solve those problems and those advances would have had even more compound value than the conservative approach. The challenge I suspect was more one of the political machinations to keep the project afloat. A more aggressive approach might have killed the project from a budget/politics perspective.
> I can only imagine the utter delight of astronomers, physicists, and scientists who have worked directly on this project. Bravo to you all.
Perhaps Berger should also credit the engineers, team leaders, administrators, etc. who proved Berger wrong, and the American, European, and Canadian citizens who had enough vision to fund it.
Gotta really appreciate everyone that put in the effort to make this particular project not a horrific, graphic failure. Of course the science returns haven't come in yet and there's still plenty to go wrong but at least it got off the ground and unfolded.
This was a lot of money for some very pure science. If it had blown up on the launch pad (a French launch pad, where government employees were presumably paid to be on a tropical island in December) it would have been Exhibit A in the case against government funding of science for the next 50 years.
the French launch pad isn't on an island, but rather in the continental South America, at the start of the rain season, so it's not exactly my type of dream posting
Learning about the intricacies of the design and especially the deployment process, and then following the team's incredible badass successes has been one of the most heartwarming and inspiring experiences of this otherwise awful epoch. Bravo, and thank you, and can't wait to see the pictures.
There were DARPA-funded projects back in 2004 to try to avoid doing it like this, while it was being built. They were funding investigations into assembling the satellite on orbit, e.g. send up the segments one at a time and dock them together on orbit. Those projects were cancelled in W. Bush's second term after he pushed for manned missions again. To this day, I still think in space assembly would have been cheaper and possibly lower risk.
Is it that? Or is it maybe a sign that the current era is a little hyper-critical and in that hyper-criticality lost touch with what's actually possible and acceptable risks? This was no small engineering feat. It's also a good demonstration of the world of the possible.
Not too many other stars around, and none that are brighter than it within almost a half degree radius. If I zoomed in to the 0.0367 degree FOV of Webb's NirCam instrument, we would only see one other very faint ~21 mag star. However, Webb (and Hubble) can see much fainter stars than Gaia.
You don't want to calibrate against something interesting, because of you see something crazy, you'll never really be all that sure it isn't because your instrument is goofy.
Astronomy has long had an issue with this. Back in the late 19th century when the magnitude system was being formalized, an astronomer named Norman Pogson chose Vega to calibrate the system because it is easy to observe in the northern hemisphere. In this system, which came to be the most dominant magnitude system, Vega by definition has a magnitude of 0 in any filter.
There turned out to be two issues with this choice. The first is that Vega has a very unusual spectrum for a star. This means that more normal stars appear to have weird differences in their magnitudes between different colors. But it's not the stars themselves that are weird, it's just a weird choice of zero points!
A more serious issue became apparent when CCDs became more common in the 1970s and 80s. It turns out that Vega is somewhat variable. You can define the zero point of the magnitude system to be the average brightness over a long period of time, but that doesn't really help you on any given night since the equipment needs to be calibrated daily (or more frequently --- temperature and atmospheric changes require re-calibration).
Another source of annoyance here is that Vega is also very bright. This was a benefit in the days of photographic plates. But modern telescopes with CCDs cannot observe such a bright star. It almost immediately. So this makes calibrating the equipment trickier. (You essentially need a two step process where you use a small, specialized device to calibrate against Vega and then measure the flux from a dimmer reference star, and then measure the reference star with your telescope.)
It may be that they don't want to use too bright a star because it would saturate their detectors, so perhaps they picked dim, but not too dim, in the right direction.
Edit: the link posted by muds while I was writing this gives the explanation.
Readit News
I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one.
Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie.
And rather than have a fearsomely complex integrated sunshield, you could have a similar swarm of simpler satellites that provide a large cool area at L2, and then the observers just need to handle their own heat.
I suppose this could be described as microservices...in spaaaaace. Draw what parallels you will from that!
[1]: https://www.life-space-mission.com/ [2]: https://lisa.nasa.gov/
Producing novel observation platforms is going to be expensive regardless of which platform, because of launch costs.
> I wonder if a future evolution of space telescopes will be some kind of interferometric (obviously extremely hard for IR or visible light, but easier for radio and microwaves) swarm of cheap semi-disposible telescopes than one enormous one.
With space recovery and repair mission capabilities like https://nexis.gsfc.nasa.gov/osam-1.html growing, a single large asset could be easier to repair than constant refresh.
Anyways, small satellites = small sensors.
There is a big difference between a projected life of 1-3 years, and a prestige mission with a long lifespan. Hubble has been operating for ~30 years now.
> Then you can add to the swarm, upgrade elements, and retire failed elements without having to eat a multi-billion helping of humble pie.
Keeping a swarm of space assets ideally situated over time, with proper attitudes and control is a non-trivial problem. Look at Magnetospheric Multiscale Mission, that is considered a hard problem.
Software solutions don't always translate to hardware.
This is exactly the point: launch costs are coming down, and there is widespread anticipation that they will start to plummet as the next generation of launchers comes online. If/when Starship (a) becomes available + (b) has any significant competition, launch costs could plummet by an incredible factor.
Right, and the GPS constellation has been active for almost thirty years too. I think the GP is probably right that it would be great if the risk associated with a single mega launch/deployment could be spread over a fleet, but ultimately it does no good if you can't use that configuration to get the observations you want, hence the question. It has less to do with it being a "software solution" and more just whether it would actually practically work.
To their point, though, lots of ground-based radio telescopes are now also arrays of many dishes [1], so it's not at all hard to imagine that a similar configuration could be of value in space.
[1]: https://public.nrao.edu/telescopes/vla/
And yes, they have small elements, that's the whole point. A small element is disproportionately easier to produce than a bigger one. The point of The Swarm would be to offset the small area individually small elements with a large number of them. ALMA does this, and they even pick the dishes up with giant forklifts and move them around to reconfigure the array.
Optical interferometric arrays are very hard and only recently even possible, so it's unlikely you could do it in space "soon" (even LISA is still a long way out, and that's been planned since I was at school). I obviously don't have a handle on if the added noise from positioning errors outweighs the literally astronomical baseline advantage.
And yes, Hubble might have lasted 30 years, but JWST has about 10 years life, and then it's dead and will fall away from L2 unless they can get a refuel/regas mission launched (it does have the ports for it) to it in time.
Of course any number of practical issues can torpedo such a thing from the phase space of feasible implementations, but they're still fun to think about.
Is there anything other than manoeuvring/orbit-correction propellant that puts an upper limit of t5he James Webbs projected life? (At least until micro meteors trash too much of the optics?) Is it possible a resupply mission capability could effectivel7y extend its useful life indefinitely? (Did they even bother putting a fuel filler on it?)
Annother option with some of these cheaper launch vehicles is to build the telescope into the upper stage, using it as a bus/platform. So for example you could convert a Starship upper stage into a telescope, using its full 9m diameter for a mirror. Fully assembled on the ground before launch.
According to the simulations performed in [1], an aragoscope of 1km would be able to directly image objects the size of Jupiter's moons (so basically exoplanets even on the small side) 23 light-years away.
EDIT: Took the time to scavenge the numbers: JWST has 0.1 arcseconds angular resolution, a 100m aragoscope would have a 1 milli-arcsecond angular resoulution, a 1km aragoscope 0.1 milli-arcsecond which translates to be able to alpha centauri in a 70x70 pixels patch (and so see its sunspots) or as I mentioned above exoplanets on the smaller scale at 23 light years away (Europa is 1560 km in diameter).
[1] https://www.nasa.gov/sites/default/files/atoms/files/2014_ph...
in recognition of getting old(er), i wonder how many youngins even know there's a reference to be caught here.
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On duckduckgo I only found some references to The Muppets, a Springer article and a streaming playlist on archive.org
But the entropy of a large system is low, because it's physically attached with the Strong Force of physics. There is a low risk to other neighbouring satellites (space junk collisions). A swarm of small satellites has high entropy, and is loosely-coupled with the Gravity force of physics.
At what point do we want to accept the financial tradeoffs involved? Humans and the economy also benefit from the large projects, and the management structures also teach efficiency to more people who can go on to create other exciting new sensors.
We could start with a small satellite like Sputnik, and make them grow. Eventually it will reach a point of stability with the neighbouring environment. That could be much larger than we expect. "That's no moon, it's a spaceship!"
An L2 swarm isn't bound together by gravity, it actually has to maintain active control to stay there, so it's a "self cleaning" area.
I'm going to go and assume that you used the strong force and gravity as metaphors here.
I'm so pumped to see what science and images the Webb produces.
Could 2022 be the year we find an exoplanet with conclusive biomarkers?
Dead Comment
There is a cogent response to that, as a series of questions.
1 - Which requirements changed?
2 - Which hard science & engineering problems had to be solved, and how trivial, or monumental were they?
3 - Which components failed, or passed testing, requiring rework, or re-engineering?
> Selling a program to taxpayers as a 500 million dollar endeavor and then extracting ten billion dollars from them is the kind of thing that should put people in prison for life.
Initial estimated costs were higher than 500 million. The 500 million number was an NGST estimate, right? I don't think lifecycle costs were ever estimated at 500M, it seems crazy to be that low. Are you sure you are correct on the type of costs you are providing?
And you are posting this on a forum dominated by software engineers?
Sometimes it's good to overspend if it's an excuse to fund research that would otherwise struggle to find money to stay alive.
Plus I think the budget didn't jump from 500 million to ten billion dollars in on day, project grew and budget grew with it, and someone had to approve it, we are talking about multinational project, so I think everything is well documented and well approved from people who knows the project well better than us.
I do agree with you that if that was military budget, I would think that something is really wrong.
On another article today, again the top response to the top comment was so negative that dang stepped in, and yet again, it's the first thing you see.
It's frustrating, because HN is doing a great job keeping things pretty constructive, but this still seems to reward negativity by thrusting it into view. Shouldn't it at least be below less-downvoted responses?
Life in prison for being over budget...
Would you say the same about LIGO, for example? Originally thought to be easy, it turned out to be a 40 years long endeavor.
In 2019, NASA's Astrophysics Division finished up two years assessing the feasibility of assembling a large-aperture observatory in-space. The In-Space Astronomical Telescope (iSAT) Assembly Design Study [1] concluded that In-Space Assembly (ISA) is the only option for building observatories with aperture diameters over 15 m and would still likely be strongly beneficial for smaller ones like the JWST (6.5 m aperture diameter). Efforts like Northrop Grumman’s successful Mission Extension Vehicles, the upcoming DARPA RSGS and NASA OSAM-1 missions, and the usage of Canadarm2 to install instruments with standardized interfaces on the outside of the ISS all demonstrate the increasing maturity of robotic servicing and assembly. The iSAT study describes a telescope composed of modules with standardized interfaces, launched with a spacecraft bus that has attached Canadarm2-like robotic arms that can assemble and deploy modules delivered by space tug from multiple launches. The benefits over launching monolithic spacecraft with hundreds of single points of failure (cough JWST cough) are clear: the mission won’t be limited by a single launch vehicle’s lift ability or fairing size; the same inchworming robotic arm that does initial ISA can later perform repairs and upgrades, either with freshly delivered replacement modules or by debugging malfunctioning parts (see Mars Insight); the final deployed structure doesn’t need to be designed to handle harsh launch conditions; and, design and development will be faster without needing to design and test super reliable deployment mechanisms—if a part fails during orbital checkout, launch a replacement. The primary challenge is designing hardware that today’s limited-dexterity robotics can manipulate, and figuring out supervised autonomy with fallback telerobotics for bringing humans into the loop when needed. There are definitely challenges, but this feels like the right approach. If you could do it near a crewed station for infrequent debugging EVAs, even better. After it's assembled, raise the orbit to L2 with solar electric propulsion.
[1] https://exoplanets.nasa.gov/exep/technology/in-space-assembl...
I'll be writing about this more in Orbital Index (https://orbitalindex.com) sometime soon.
"Neutral Buoyancy Evaluation of Extravehicular Activity Assembly of a Large Precision Reflector" (https://arc.aiaa.org/doi/10.2514/3.26480)
> The procedure and associated hardware are verified in simulated 0-g (neutral buoyancy) assembly tests of a 14-m-diam precision reflector mockup. The test article represents a precision reflector having a reflective surface that is segmented into 37 individual panels. The panels are supported on a doubly curved tetrahedral truss consisting of 315 struts. The entire truss and seven reflector panels were assembled in 3 h and 7 min by two pressure-suited test subjects.
It would be good to develop that capability, but maybe do some trial runs on assembling something a little smaller, and less critical?
[1] Human orbital assembly of the JWST is not possible, because we do not have any crewed vehicles that can make the trip.
I was assuming that GP meant "assembly in Earth orbit" and then the JWST could then rocket off on its own, fully-assembled. (Or, if they didn't mean it that way, I mean it that way.)
Perhaps Berger should also credit the engineers, team leaders, administrators, etc. who proved Berger wrong, and the American, European, and Canadian citizens who had enough vision to fund it.
This was a lot of money for some very pure science. If it had blown up on the launch pad (a French launch pad, where government employees were presumably paid to be on a tropical island in December) it would have been Exhibit A in the case against government funding of science for the next 50 years.
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Here is a 1 degree wide view of the neighborhood around HD84406 rendered from Gaia EDR3 data:
https://bsrender.io/sample_renderings/hd84406-1deg-m18-ax100...
Not too many other stars around, and none that are brighter than it within almost a half degree radius. If I zoomed in to the 0.0367 degree FOV of Webb's NirCam instrument, we would only see one other very faint ~21 mag star. However, Webb (and Hubble) can see much fainter stars than Gaia.
There turned out to be two issues with this choice. The first is that Vega has a very unusual spectrum for a star. This means that more normal stars appear to have weird differences in their magnitudes between different colors. But it's not the stars themselves that are weird, it's just a weird choice of zero points!
A more serious issue became apparent when CCDs became more common in the 1970s and 80s. It turns out that Vega is somewhat variable. You can define the zero point of the magnitude system to be the average brightness over a long period of time, but that doesn't really help you on any given night since the equipment needs to be calibrated daily (or more frequently --- temperature and atmospheric changes require re-calibration).
Another source of annoyance here is that Vega is also very bright. This was a benefit in the days of photographic plates. But modern telescopes with CCDs cannot observe such a bright star. It almost immediately. So this makes calibrating the equipment trickier. (You essentially need a two step process where you use a small, specialized device to calibrate against Vega and then measure the flux from a dimmer reference star, and then measure the reference star with your telescope.)
Edit: the link posted by muds while I was writing this gives the explanation.
- Available for observation for a prolonged time
- A star that has just entered its field of view
- Don't want a star in a field that is too crowded
- The star should be bright, but probably not too bright