Barely worth to launch another one. It would be more cost effective to invest some R&D into building a telescope with a different target wavelength to get more science than if you had two of the same telescope. The engineers will also absolutely want to fix any issues they found in Webb already.
The degree to which science has advanced since the Webb project started can't be understated either. We have a fundamentally better understanding of the technology available and what we even want to look at. Much better to simply move onto the next project, of which there are currently very many.
Was going to reply along these lines. I was fortunate to live with someone who was working on the James Webb and telling me excitedly about it — back in 2006! Surely even with the various upgrades/spec changes/delays, things have moved sufficiently that whatever is started even today will be a marked upgrade.
In any event, many many areas to aim at, and relatively limited funding unfortunately.
Paul Sutter has a great astronomy and physics podcast called "Ask a Spaceman". His "Five Exciting Missions After James Webb" episode (20 min) got me really excited for the future: https://www.youtube.com/watch?v=DiYVsoxbxAI
I'd like to see a deep space version of the Gaia astrometry space telescope.
It measures the parallax shift of stars, and is basically the one reliable way of directly measuring how far away a star is from us. Unfortunately, it's at L2, and therefore has a baseline of 1 AU. Another Gaia way out at 20AU would have capacities no Earth-based telescope could ever have.
This seems like the kind of thing where two would actually be useful. Is there any benefit to making both observations at the same time? Or are the scales so great that it doesn't really matter?
You'd almost certainly want to launch several. You get one data point per half-orbit, when you're at opposite sides of the Sun. This is tolerable for the Earth, where an orbit is one year. But a full orbit out at 20AU takes eighty four years! Collecting a useful number of samples with one spacecraft would take centuries, while two spacecraft in opposition on the same orbit can measure parallax instantly.
There has been a lot of work on earth based telescopes (eg the 30 meter, giant Magellan, and some array based telescopes) that are going online in the next decade.
For the most part, yes, with adaptive optics and corrective measures being taken to deal with more satellites in orbit, ground telescopes are superior or at least comparable to space telescopes given their ability to be much larger.
Space telescopes these days are primarily being designed for observations that simply can't be done while in the atmosphere (eg the wavelengths JWST and NGR look at). The value of a space telescope in the same wavelength range as what ground based telescopes usually use would mainly benefit in terms of being able to have much longer exposures.
Yes they are very much possible, and cheaper than space too.
What starlink does is ruin part of the images, and if the thing you were interested in observing happens to be blocked by a starlink trail you're hosed: a thing literally blocked what you tried to see and you lost the nigh (because usually you get just a bit of the a night for your observation). Other things that ruins your night is clouds, so starlink effectively makes the weather at a site worse, only you find out after the night that it was all a waste.
To some extent you can plan around it, but as the mega constellations grow they'll have to avoid each other more frequently and there's no rules for how that shits coordinated, so you maybe you can know in advance that the night is wasted.
But the risk that a satellite is in an undocumented orbit by the time you try to observe will likely be very high in the future.
Have you taken a photo while someone else used a flash? The flash is also only on for a fraction of the camera exposure but you sure as hell notice when it happened and it went off close to what you wanted to depict you will just have to take a new photo.
The length of the occlusion isn't very relevant when the thing going in front is orders of magnitudes brighter than what you are trying to observe.
a leo telescope doesn't look anything like a star (mainly because it's moving too fast). the way you deal with this is by not taking hour long exposures, and instead take thousands of second long exposures. then you can composite them all together, cropping out the bits that look like satellites from each frame. it's a little annoying, but pretty easy to automate.
My understanding is ground based telescopes imaging in the same wavelengths also have to deal with distortion in the atmosphere, star link interference would be easier to filter out compared to the other stuff (which is why locations for these mega ground based telescopes are chosen with utmost care )
Disclaimer. Not a physicals or astronomer, just a enthusiastic backyard amateur astronomer who reads a lot about telescopes .
How do you figure? A fleet of space telescopes research teams could interact with through an API without much cost and zero approval, would for sure advance science by a lot. I find it weird to see a statement like this, so maybe you have something else in mind. It's a stretch to go from "building a different one would give new classes of insights" to "having more people being able to use this thing we only have 1 of a kind is barely worth it".
> A fleet of space telescopes research teams could interact with through an API without much cost and zero approval, would for sure advance science by a lot.
100 % someone would point at the sun by accident and burn all the sensors within six months if access is unrestricted and the api is powerful.
In any case easy access to data will mostly result in data lying idle on disks somewhere because people are busy doing something more interesting. Analysing data is many months of work, and you don't get more months just because there is more data.
I wonder how feasible it would be to count on Starship to succeed, so that each flight could deliver one hexagonal mirror segment, eventually culminating in a giant composite mirror
Based on how JWST folded up, the width of the hexagonal segments is already a sizable chunk of its overall launch diameter. Doing what you suggest could absolutely result in a bigger overall telescope, but the complexity would be increased vastly more than the overall telescope diameter.
You would not need to fold it at all. Instead, launch dozens of Webb-scale scopes for a fraction of the price, able to point in that many directions at once.
I don't think you understood what I meant. If you launch the segments by themselves, the width of a single segment would still be limited to the internal diameter of the launch vessel, we're not going to just bolt a naked mirror to the front of a rocket.
If you compare how the JWST was folded, the width of the individual segments was already close to the maximum allowable diameter of the launch vessel. Leaving the rest of that launch vessel empty won't get you a much bigger final mirror.
JWST folded is about 3 tiles wide, in a housing 4.7m in diameter, unfolding to 6.5m. So a JWST style fold in a Starship would be double. A one-mirror-segment-per-flight would be something like 36m, in the same arrangement. But since you would be constructing from separate sections, the diameter is theoretically limitless.
Just stack the mirrors inside Starship, and assemble them in space.
Below, an example of a 300m diameter telescope using 8-meter mirror segments assembled in-orbit
I guess in-orbit assembly would then be a whole different can of worms. But, a very useful can of worms - once it's figured out, it's like horizontal scaling - you can just keep sending up more parts.
