Can telescopes in space replace ground based telescopes?

[Marci]

"Astronomers should be happy about SpaceX. Cheap access to space will enable a lot of space telescopes, no worries about mega constellations disturbing ground based astronomy"


This is one of the most common answers one can read when talking about effects of starlink and other satellite constellations on ground based telescopes. Even from people like Everday Astronaut or Elon Musk himself. My feeling is that this is not a very realistic argument but I want to learn more about it and hear some thoughtfull opinions on this topic?

Let's say Starship will be flying soon and it will actually be very very cheap. Can you really replace ground based telescopes? What types of research/wavelengths could be done in space? And what types of research need to be done on the ground and why?

[Proponent]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

[TorenAltair]

I think neutrino telescopes are better on or more precise under Earth.

[su27k]

The idea is not to totally replace ground based telescopes, at least not in the short term, but to compensate the loss of the ground based observation time caused by mega constellations. This latter loss would require a lot less space telescopes than a total replacement, especially considering space telescope can work 24x7 while ground telescopes can only work at night and under good weather conditions.

[hop]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

Yeah, "we'll just put the telescopes in space" is just fantasy. All else being equal being in space would be generally better for optical and radio, but in real life things aren't remotely equal. Doing things in space is really expensive, even if the launch is free.

Large ground based telescopes are already ~billion-dollar projects, with development timelines measured in decades. The big ground based observatories that will operate though the 2030s are already being built, with billions of dollars committed in hardware and multinational agreements. Even if Starship were available tomorrow and launch was free, LSST, GMT, TMT and ELT aren't going space. Designing space missions to accomplish the same goals would mean starting over from scratch, at the cost of many billions of dollars and years (if not decades) of development. The instruments for these things can already cost hundreds of millions. Building equivalent systems to operate in space could easily cost an order of magnitude more.

It's equally absurd at the low end: A lot real astronomy is done with small telescopes on tiny budgets. The budget for something like Dragonfly would be absolutely swamped by the cost of a spacecraft bus capable of supporting it.

[ZChris13]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

Yeah, "we'll just put the telescopes in space" is just fantasy. All else being equal being in space would be generally better for optical and radio, but in real life things aren't remotely equal. Doing things in space is really expensive, even if the launch is free.

Large ground based telescopes are already ~billion-dollar projects, with development timelines measured in decades. The big ground based observatories that will operate though the 2030s are already being built, with billions of dollars committed in hardware and multinational agreements. Even if Starship were available tomorrow and launch was free, LSST, GMT, TMT and ELT aren't going space. Designing space missions to accomplish the same goals would mean starting over from scratch, at the cost of many billions of dollars and years (if not decades) of development. The instruments for these things can already cost hundreds of millions. Building equivalent systems to operate in space could easily cost an order of magnitude more.

It's equally absurd at the low end: A lot real astronomy is done with small telescopes on tiny budgets. The budget for something like Dragonfly would be absolutely swamped by the cost of a spacecraft bus capable of supporting it.

SpaceX are also trying to bring down the cost of a satellite bus, with their Starlink production line. Of course, getting good enough pointing accuracy might not be so easy, and Starlink isn't the best form factor for a telescope, but they're not alone. The costs for a cubesat is also quite low.

[meberbs]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

Yeah, "we'll just put the telescopes in space" is just fantasy. All else being equal being in space would be generally better for optical and radio, but in real life things aren't remotely equal. Doing things in space is really expensive, even if the launch is free.

...The instruments for these things can already cost hundreds of millions. Building equivalent systems to operate in space could easily cost an order of magnitude more.

Things are expensive in space because you cant fix them if they break, and other overdesigning issues that are required for special one off missions. If Starship is running cheap launch of large things, you don't have to worry about that so much, and the marginal cost of doing it in space will be in the noise relative to the rest of the project cost

It's equally absurd at the low end: A lot real astronomy is done with small telescopes on tiny budgets. The budget for something like Dragonfly would be absolutely swamped by the cost of a spacecraft bus capable of supporting it.

Yeah, not like anyone could put a hundred cheap telescopes in orbit today capable of operating 24/7. Oh wait, that has already been done, they just pointed them at the Earth. With cheap frequent launch there is no reason reasonable size telescopes like that could not be supported on equal inexpensive buses.

And as has been mentioned above, the near term bar should just be eliminating the net impact to observations due to upcoming constellations. That whole being in Earth's shadow while overhead during the night really kills the visibility impact of most satellites over most of the sky most of the time. Few telescopes have significant need for near horizon observations for science work that I know of, often it is less useful due to more interference from the air. One exception I have heard suggested was searches for PHAs, but those should be particularly helped by IR sats in orbit. In general productivity, one telescope on orbit probably could replace at least 2 slightly more capable ones on the ground completely. If all you want to do is replace the bit of interference that upcoming constellations will cause with certain observations, it doesn't take all that much.

We have another thread on actual impacts going on for a while, but I haven't read the whole thing, has anyone actually done a calculation/simulation yet showing what real impacts would be? Preferably one that accounts for the fact that satellite passes are predictable and can be dodged entirely in many cases.

[ZChris13]

No, unfortunately meberbs that entire thread is two or three people arguing the same points back and forth. It's mostly quieted down now, so it's safe to skim it, but there hasn't been a whole lot more math than pointing out that the math used to fearmonger was kind of bogus.

[meberbs]

No, unfortunately meberbs that entire thread is two or three people arguing the same points back and forth. It's mostly quieted down now, so it's safe to skim it, but there hasn't been a whole lot more math than pointing out that the math used to fearmonger was kind of bogus.

Thanks, that is what I thought, I had looked at the thread some. (And I admit to being one of the 2 or 3 people in certain other threads (usually new physics) that ended up similar, so I get how that happens.)

It has been long enough that if a specific astronomy mission was going to have major irrevocable impacts, someone probably would have quantified them by now, and knowing this site, someone would find that quickly. In my mind, the lack of such a report puts a loose bound on how severe the impacts can get. I expect one will eventually get published one way or another to guide future missions.

[woods170]

Can telescopes in space replace ground based telescopes?

Yes, technically they can. Hubble in particular is a very fine example.

A large part of the electromagnetic spectrum is not visible to ground-based telescopes anyway. Think Gamma ray, X-ray, Ultraviolet, most of the Infrared spectrum and long wavelength Radio.

In the past several decades, a very substantial number of space-based telescopes has gone into orbit to observe said parts of the electromagnetic spectrum. A whole bunch of X-ray telescopes and Ultraviolet telescopes, a good number of Infrared observatories and some Gamma ray missions as well (Compton, BeppoSAX, HETE-2, Swift, INTEGRAL, Fermi and AGILE).
Heck, there have been even a few Radio astronomy satellites: HALCA and Spekr-R.

[libra]

No. They are complementary, and adaptative optics can cancel most of atmospheric disturbance.

Also, astronomers are no idiots - the fact that  30 m and 39 m ground-based telescopes (EELT) are currently build can not only be explained by the high cost of space launch, with or without SpaceX.

Incidentally, even with BFR/BFS, sending a 30 m or 39 m mirror into space won't be easy anytime soon.

As for multiple mirror telescopes like the defunct TPF & Darwin, ground-based variants also exists. Antoine Labeyrie, a genius astronomer that pioneered visual light interferometry, has explored ground-based and spaceborne concepts.

Ground-based with adaptative optics and smaller spaceborne telescopes are complementary, not mutually exclusive.

[libra]

Yeah, not like anyone could put a hundred cheap telescopes in orbit today capable of operating 24/7. Oh wait, that has already been done, they just pointed them at the Earth.

Bouncing off this even if I don't agree with Meberbs arguments.

Fact is that the NRO launched
- 144 KH-7 and KH-8 GAMBIT spysats, each one with a 48 inch mirror
- 20 and counting, KH-11 and whatever followed them, each one with a 94-inch mirror

- plus the cancelled KH-10 DORIAN MOL
- of which six 72-inch mirrors were build and later handled to Aden Meinel for the Arizona MMT telescope.
- Plus the NRO declassified documents showing that NASA wanted these mirrors in 1969
- and also asked the spooks if, someday, they could point a KH-10 at Mars or Jupiter to try and get some interesting pictures.

So the NRO kind of launched 170 high-tech mirrors in space since the first KH-7 in 1963  ! makes one think... it is no surprise NASA was either jealous or willing to collaborate with the spooks... to get their technology. 

[meberbs]

No. They are complementary, and adaptative optics can cancel most of atmospheric disturbance.

Most is not all, this does nothing to support your argument, as you don't list a single capability that is lessened by being in space (they really isn't a meaningful one.)

Also, astronomers are no idiots - the fact that  30 m and 39 m ground-based telescopes (EELT) are currently build can not only be explained by the high cost of space launch, with or without SpaceX.

No, astronomers are not idiots, so it is simply insulting when you use their name to make such baseless assertions. The inability to launch said telescopes to space at an affordable price is plenty of reason to build them on the ground instead.  You provide no other explanation.

Incidentally, even with BFR/BFS, sending a 30 m or 39 m mirror into space won't be easy anytime soon.

Such telescopes are already built out of numerous bite sized mirrors, And if that wasn't enough, the telescope could be launched in pieces, and even have astronauts assemble it on orbit (cheap human launch is also a capability of BFR/BFS.)

As for multiple mirror telescopes like the defunct TPF & Darwin, ground-based variants also exists. Antoine Labeyrie, a genius astronomer that pioneered visual light interferometry, has explored ground-based and spaceborne concepts.

Why would ground based equivalents of some space based telescopes existing have any relevance to the question at hand, whether space based equivalents can exist for ground based telescopes?

Ground-based with adaptative optics and smaller spaceborne telescopes are complementary, not mutually exclusive.

No one has said that they are exclusive, the topic of the thread asks if there is anything that needs to be done on the ground, where interference from Starlink or other large constellations could not be mitigated by instead doing it from an on orbit telescope, given cheap, highly capable launch.

Yeah, not like anyone could put a hundred cheap telescopes in orbit today capable of operating 24/7. Oh wait, that has already been done, they just pointed them at the Earth.

Bouncing off this even if I don't agree with Meberbs arguments.

Fact is that the NRO launched ...

You seem to have missed my point, I thought it was clear that I was referring to a much more recent commercial company. You aren't exactly helping your case here either way though.

[Proponent]

A large part of the electromagnetic spectrum is not visible to ground-based telescopes anyway. Think Gamma ray, X-ray, Ultraviolet, most of the Infrared spectrum and long wavelength Radio.

A minor point about the graphic:  astronomers do observe the heavens at wavelengths below 1 mm from the ground, albeit only from very elevated portions of ground.  From a very good site like Mauna Kea, observations down to 0.3 mm are possible, say, one night in ten  -- it depends on the amount of water vapor in the atmosphere.

[Hobbes-22]

There's a list of astronomical observatories on Wikipedia. It has ~800 entries, and that's just the professionals. There's also an amateur community that provides professional-grade observations. It'll take quite a few launches to replace those.

I'm not convinced comparisons with the NRO are valid. Those sats weren't exactly cheap, and they weren't suitable for astronomy either (optimized for Earth observations at much higher light levels than astronomy).

[hop]

Things are expensive in space because you cant fix them if they break, and other overdesigning issues that are required for special one off missions. If Starship is running cheap launch of large things, you don't have to worry about that so much, and the marginal cost of doing it in space will be in the noise relative to the rest of the project cost

Cheaper, sure, but "in the noise relative to the rest of the project cost" is totally unsupported. Space is still an extreme environment. Radiation, vacuum, thermal extremes, micro gravity, launch loads all impact the cost of developing an instrument. Free-flying satellites still need a whole bunch of systems and greater reliability than some COTS electronics in a dome you can send a grad student out to bang on with a hammer.

On the ground, if a component goes bad, one low wage operator goes and swaps it out in an afternoon. That's going to be orders of magnitude cheaper than launching someone into space to do an EVA. Even if your telescope is bolted onto an already crewed space station, the overhead of a space station is going to be a lot more than a telescope operators shack.

Easy access to space doesn't completely negate the need for higher reliability. On the ground, if your software crashes someone can go and reboot it. In space, if you don't have high redundancy and complicated safing systems, it can mean LOM. Even if you have on-orbit repair capability, losing command capability will make it more complicated and run the risk of cascading failures, like batteries and propellant systems exceeding thermal limits or instruments frying themselves by looking at the sun. You can engineer your way out of all that of course, but it costs money.

Yeah, not like anyone could put a hundred cheap telescopes in orbit today capable of operating 24/7. Oh wait, that has already been done, they just pointed them at the Earth. With cheap frequent launch there is no reason reasonable size telescopes like that could not be supported on equal inexpensive buses.

Cheap launch would certainly be great for smallsat astronomy. There's interesting, useful things to be done with satellites in the class of Planet's doves. But it's a big leap from that to assuming it can replace everything that's done on the ground for similar cost. BRITE has done some cool stuff in this area, but if you read their papers, you'll find there's a lot more to it than just shoving a cubesat out the door.

That whole being in Earth's shadow while overhead during the night really kills the visibility impact of most satellites over most of the sky most of the time.

This is not as mitigating as SpaceX fans seem to think. When you think about the geometry, you need to include inclination and seasons. The reality these constellations will be a minor annoyance for some, and a significant issue for others. It is already impacting LSST planning (SpaceX is working with LSST to help mitigate the impact, but that doesn't include putting LSST into space ). The recent AAS 235 meeting had a session https://aas.org/meetings/aas235/press-kit#Sun_am and press conference on this subject.

[yg1968]

Can telescopes in space replace ground based telescopes?

Of course not. There is more and more discoveries by amateurs because it's impossible to be looking everywhere at the same time. There is strenght in numbers. Very large telescopes are still being built in Chili and elsewhere despite Hubble and other space based telescopes.

[meberbs]

Things are expensive in space because you cant fix them if they break, and other overdesigning issues that are required for special one off missions. If Starship is running cheap launch of large things, you don't have to worry about that so much, and the marginal cost of doing it in space will be in the noise relative to the rest of the project cost

Cheaper, sure, but "in the noise relative to the rest of the project cost" is totally unsupported.

Read the context of what I was responding to. They were talking about $100 milllion dollar telescopes becoming billion dollar ones. Starlink/One Web type satellites should be on the order of $1 million a piece scale that up some for bigger satellites and then down for decreasing costs as cheap launch and expanded use of space etc. In the noise seems about right compared to the driving costs including precisely ground mirrors etc contributing to the baseline cost. I never claimed that the other things you mention can be ignored completely.

Also as far as spacewalks and such for repair, there is a fundamental difference in risk between a 10% chance that you lose a $100 million instrument and a 10% chance that you spend $5 million sending someone to repair it. It fundamentally changes the acceptable risks and how much needs to be spent mitigating them.

Cheap launch would certainly be great for smallsat astronomy. There's interesting, useful things to be done with satellites in the class of Planet's doves. But it's a big leap from that to assuming it can replace everything that's done on the ground for similar cost. BRITE has done some cool stuff in this area, but if you read their papers, you'll find there's a lot more to it than just shoving a cubesat out the door.

You are mixing things here. Every capability can clearly be replicated on the ground. There is however no short term need to only do things in space. The assumption you are arguing against is a strawman.

That whole being in Earth's shadow while overhead during the night really kills the visibility impact of most satellites over most of the sky most of the time.

This is not as mitigating as SpaceX fans seem to think.

Your links do not support your assertion. In fact after looking over the linked presentations, I am becoming more convinced that this will be completely negligible. I haven't watched the whole video since it is an hour long. If there is anything in it that actually describes a real significant impact please provide the relevant time stamp. (There are a number of assertions in the video/papers that seem to be using the brightness level of the orbit raising state and applying it to everything, same presenter later makes relevant mitigating marks.) Nothing in the video says that the factors I list are not significant mitigating factors. Some are actually listed as relevant factors in fact.

When you think about the geometry, you need to include inclination and seasons.

If you think about the seasons, you see that it is better for half the year and worse for half the year. This doesn't really change anything.

The reality these constellations will be a minor annoyance for some, and a significant issue for others. It is already impacting LSST planning (SpaceX is working with LSST to help mitigate the impact, but that doesn't include putting LSST into space ).

From as far as I got in the video, it sounds like there would be no reason to put LSST in space because by planning around satellite passes and other potential mitigations, there was no assertion that there would be a net impact to the science once this was complete.

[hop]

They were talking about $100 milllion dollar telescopes becoming billion dollar ones.

You have offered no evidence that this is incorrect. Space qualifying something like the LSST camera or one of the ultra high precision spectrographs would be super expensive, even if you have a very generous mass budget.

Also as far as spacewalks and such for repair, there is a fundamental difference in risk between a 10% chance that you lose a $100 million instrument and a 10% chance that you spend $5 million sending someone to repair it. It fundamentally changes the acceptable risks and how much needs to be spent mitigating them.

Sure, it changes the risks, but $5 million is a lot more than sending your $40k/year telescope operator out to change out a $10 non-space rated electrical component they picked up at the hardware store.

Your links do not support your assertion. In fact after looking over the linked presentations, I am becoming more convinced that this will be completely negligible.

The people building LSST came to the opposite conclusion you do. The AAS abstracts unfortunately don't include the details of their analysis, but I'm sure they will be published in due course.

Fundamentally, a large number of professional astronomers believe this is a significant issue for some types of observations (though not an existential threat for most), and SpaceX enthusiasts (edit: though aside from some ill-considered tweets, not SpaceX themselves) insist it's not, often by implying astronomers don't know when satellites are visible, or saying "just put all the telescopes in space!!!!"

One of these positions is informed by deep knowledge of the relevant details.

If you think about the seasons, you see that it is better for half the year and worse for half the year. This doesn't really change anything.

That is not correct, because the value of the time at the extremes isn't equal. The point is that satellites like this can be illuminated at relatively high elevation in prime observing time.

edit:
To be clear, I agree with you that there is no need to put all ground based astronomy in space, and that many types of astronomy won't be severely impacted by mega constellations.

Where we disagree is over the idea that cheap launch would make moving ground based astronomy into space a viable option in the foreseeable future.

[meberbs]

They were talking about $100 milllion dollar telescopes becoming billion dollar ones.

You have offered no evidence that this is incorrect. Space qualifying something like the LSST camera or one of the ultra high precision spectrographs would be super expensive, even if you have a very generous mass budget.

I didn't try to prove it in general, because it is too general of a statement to do that. I gave numeric examples to support my statement though, which is significantly more evidence than your list of specific issues that you incorrectly claimed I was ignoring.

Sure, it changes the risks, but $5 million is a lot more than sending your $40k/year telescope operator out to change out a $10 non-space rated electrical component they picked up at the hardware store.

Worst case, the risk happens and you add $5 million to a $100 million budget. This is small enough relative to the budget as a whole that it is a rounding error in these order of magnitude estimates. Comparisons to what it would have cost to fix the same thing on the ground aren't relevant.

Your links do not support your assertion. In fact after looking over the linked presentations, I am becoming more convinced that this will be completely negligible.

The people building LSST came to the opposite conclusion you do. The AAS abstracts unfortunately don't include the details of their analysis, but I'm sure they will be published in due course.

The abstracts do not make the assertion that there would be non-negligible impacts to science after mitigation. Nothing I saw in the video does either. I asked for you to point specifically to where they say otherwise and you failed to do so. There is no reason to think that they have a detailed analysis which supports an assertion they don't make to begin with. As far as I can tell you are now just lying, asserting that they say something that they don't just to spread FUD.

Fundamentally, a large number of professional astronomers believe this is a significant issue for some types of observations (though not an existential threat for most), and SpaceX enthusiasts (edit: though aside from some ill-considered tweets, not SpaceX themselves) insist it's not, often by implying astronomers don't know when satellites are visible, or saying "just put all the telescopes in space!!!!"

They "believe" it is for "some types" of observations. That is about as wishy-washy of an assertion as you can get. It does not assert evidence of even a potential issue, or specifically list anything that would be negatively impacted. You then move on to talking about extreme strawmen on the other end of the spectrum rather than providing any facts.

One of these positions is informed by deep knowledge of the relevant details.

Nope, neither of them is. None of what you just listed is supported by a single fact, nor is what you just listed equivalent to what I am saying.

If you think about the seasons, you see that it is better for half the year and worse for half the year. This doesn't really change anything.

That is not correct, because the value of the time at the extremes isn't equal. The point is that satellites like this can be illuminated at relatively high elevation in prime observing time.

For what reason is the value of the observing time different? Your second statement has nothing to do with the seasons, and is the kind of thing that show be supported by math and an explanation of what you consider "relatively high elevation"

To be clear, I agree with you that there is no need to put all ground based astronomy in space, and that many types of astronomy won't be severely impacted by mega constellations.

Where we disagree is over the idea that cheap launch would make moving ground based astronomy into space a viable option in the foreseeable future.

There are a couple ways I can interpret the last sentence. One is that you are claiming that no moving of ground based astronomy to space would happen in the foreseeable  future, which is absurd because astronomy is happening in space and reduced cost of access to space will only increase how much happens there.

Another is you arguing against the point of moving all ground spaced astronomy to space in the near term, which again would just be you trying to force an idiotic strawman argument into my mouth.

I am not really sure what you could be trying to say in between, since I am only arguing that near term enough can be put into space to mitigate any impacts and you just agreed that many types of astronomy will not be severely impacted. The real disagreement seems to be whether there are any significant to severe impacts, and while I cannot go through every conceivable desired type of astronomy to prove that there is none, if there is one that is significant, it shouldn't be too hard to point out specifics, so I am not going to accept that there are such impacts without evidence. (And if there are then the question of whether those can be easily addressed with space based telescopes can be a lot more specific.)

It was mentioned above how a related thread devolved into an argument between a couple people, lets not do that again here. If you have some facts to share please do. If you are just going to argue against strawmen, or point to vocal astronomers on twitter making vague complaints, please don't.

[hop]

For what reason is the value of the observing time different? Your second statement has nothing to do with the seasons, and is the kind of thing that show be supported by math and an explanation of what you consider "relatively high elevation"

This is astronomy 101. Higher elevations, lower airmass, darker sky. To what extent this matters depends on the details, but in general, you can go deeper/get better data if you're looking straight up in full darkness. Hence, people trot out the "you only see starlink at twilight and they're mostly in shadow" argument to claim (incorrectly) that the impact on real astronomy is negligible.

This is doubly wrong: Some observations necessarily have to look at low elevations near twilight, and satellites in LEO orbits can be seen quite high and late.

there is no reason to think that they have a detailed analysis which supports an assertion they don't make to begin with.

They have done the analysis and made the statement:
https://www.aura-astronomy.org/news/aura-statement-on-the-starlink-constellation-of-satellites/

The LSST Project Science Team has been simulating the potential impacts to LSST observations. Their latest update of preliminary results from November 2019 indicates that (assuming the full deployment of planned satellites) nearly every exposure within two hours of sunset or sunrise would have a satellite streak.

(my emphasis)

I've seen first hand statements from LSST people that they are very concerned and have done significant analysis. They are modifying their observing strategy and even the camera readout to try to mitigate it. The observing strategy is something that's been subject to years of debate and optimization, so it's likely that science will suffer, even if they manage to meet the baseline goals. It also depends a lot on how many of the constellations get built, what orbits they end up on, and how bright they end up being.

This thread has some details from the actual presentation at AAS:
https://twitter.com/Thomas_Connor/status/1215010589791019009

I also know first hand that other surveys like Super-ASASSN are significantly affected. NEO searches are also likely to be heavily affected, since they necessarily need to look relatively close to the sun. Some statements from Pan-STARRS
https://www.mauinews.com/news/local-news/2019/06/more-satellites-in-space-streak-mar-telescope-images/

Another is you arguing against the point of moving all ground spaced astronomy to space in the near term, which again would just be you trying to force an idiotic strawman argument into my mouth.

That "strawman" is literally the subject of the thread "Can telescopes in space replace ground based telescopes? ", and common refrain of the people who claim Starlink won't be a problem, including Musk himself in his initial reaction.

edit:
I recognize you aren't making the argument that we can just put everything in space. I think your assumptions about how cheap lift will affect the cost of doing astronomy in space are extremely optimistic, but I'll freely admit the uncertainties are large.

[Lar]

My take: The answer to the question posed by the OP? No. Space telescopes cannot completely replace ground ones (and vice versa). BUT SpaceX could easily give astronomy and astronomers access to new telescopes that make up for the loss and even exceed current capabilities for not a lot of coin.

[Coastal Ron]

We may need someone to come up with a new generation of low cost space telescopes in order to leverage the lower launch costs that the SpaceX Starship provides in order to fully replace Earth-based observation platforms.

But I think the success of the (now) 30 year old Hubble Space Telescope has shown us what a small 2.4m diameter telescope can do in space. Imagine if we could build lower cost 8m diameter telescopes and do final assembly in space, then move them to regions of space that provide unobstructed views?

In the Project Management Triangle you have the option of Good, Fast, and Cheap, but you can only have two of them (at most). The Hubble Space Telescope took 20 years from proposal to launch, and the James Webb Space Telescope will have taken 25 years if it launches in 2021.

It is the cost of the telescopes, and the speed at which they are built, that will determine if space telescopes can leverage the significantly lower cost of transportation that New Glenn and Starship will be able to provide.

We will need an Elon Musk for space telescopes... 

[Zed_Noir]

<snip>
It is the cost of the telescopes, and the speed at which they are built, that will determine if space telescopes can leverage the significantly lower cost of transportation that New Glenn and Starship will be able to provide.

We will need an Elon Musk for space telescopes... 

Please stop giving the SX CTO more ideas for shiny objects.

[Eka]

Something that fundamentally needs to be acknowledged is near Earth space will increasingly get more and more crowded over the next few decades. SpaceX's Starship, with it's low cost to orbit, will help make sure this starts to happen. Others will copy and follow in it's wake. Starlink is just the start.

<snip>
It is the cost of the telescopes, and the speed at which they are built, that will determine if space telescopes can leverage the significantly lower cost of transportation that New Glenn and Starship will be able to provide.

We will need an Elon Musk for space telescopes... 

Please stop giving the SX CTO more ideas for shiny objects.

He could be a great resource for setting up a space telescope manufacturing facility. One of the big issues I see with all space telescopes so far is everything is a one off part. They need to be built in batches to get the cost per telescope down. Making 10 or 20 of a part is often far cheaper per part than making one. Once the design is done and the machinery is setup for the first, why not make a few more copies and save all that design and setup costs.

Now if you have a new telescope going up every few months, adding some new instrument design isn't a long wait. It becomes how long does it take to design, build it, and how long the queue for instrument slots is.

Incremental changes to the design can be done. Major changes will need to wait for the next series.

Service will also be cheaper because of the lower cost to orbit, plus "ride share". Have an old space telescope that needs cleaning and updating, or has broken down. Send the next new one up in it's orbit, and have the delivery Starship grab the old one and bring it home. It can then be cleaned, refurbished, and have new instruments mounted, and be sent back up.

[envy887]

This thread has some details from the actual presentation at AAS:
https://twitter.com/Thomas_Connor/status/1215010589791019009

Jonathan McDowell posted the slide deck for that presentation on his website:

https://planet4589.org/space/misc/Seitzer.pdf

[hop]

My take: The answer to the question posed by the OP? No. Space telescopes cannot completely replace ground ones (and vice versa). BUT SpaceX could easily give astronomy and astronomers access to new telescopes that make up for the loss and even exceed current capabilities for not a lot of coin.

Yes, there's no doubt that cheap, routine access to space would be a huge boon to astronomy, and if the optimistic scenarios pan out, ultimately do more to advance the science than anything lost to the LEO constellations. However, it should be clear that this isn't a mitigation for impacts on programs like LSST that will be operating over the next decade.

One other thing to note, just being in space isn't enough to avoid the impacts. Starlinks are above ISS, and some of the proposed constellations would be well above Hubble. Satellite trails interfering Hubble observations is already a thing that happens. Of course, astronomy satellites can be in higher orbits, or L2 etc, but that brings it's own complications.

[meberbs]

For what reason is the value of the observing time different? Your second statement has nothing to do with the seasons, and is the kind of thing that show be supported by math and an explanation of what you consider "relatively high elevation"

This is astronomy 101. Higher elevations, lower airmass, darker sky. To what extent this matters depends on the details, but in general, you can go deeper/get better data if you're looking straight up in full darkness. Hence, people trot out the "you only see starlink at twilight and they're mostly in shadow" argument to claim (incorrectly) that the impact on real astronomy is negligible.

You apparently did not understand my question at all, you had asserted that the value of observing time is different depending on season to cancel out that impacts from seasons where there is more of a problem or less of a problem cancels out. Most of what you just said is simply irrelevant.

This is doubly wrong: Some observations necessarily have to look at low elevations near twilight, and satellites in LEO orbits can be seen quite high and late.

"Some observations" my next question should be obvious: what specific observations? (Check back in this thread, I already addressed the only one I have seen mentioned specifically)

there is no reason to think that they have a detailed analysis which supports an assertion they don't make to begin with.

They have done the analysis and made the statement:
https://www.aura-astronomy.org/news/aura-statement-on-the-starlink-constellation-of-satellites/

Thank you for providing this, I have been asking for an actual analysis with numbers since the first post I wrote in this thread.

I would be significantly more grateful if you didn't make me ask for it 3 times before actually supporting any of your assertions with facts.

I have significant questions about what they used as inputs to the analysis, because "nearly every" does not seem like a plausible result. At the least this probably ignores the mitigations mentioned in your previously provided links. The statement you quoted does not clarify how much of the 2 hours is actually useful to begin with, and the next sentence almost seems to contradict it with statements about 40% (or less) of twilight observing time impacted. The statements about saturation in the link in particular are questionable since Starlink sats in operation should be +4 to +7 magnitude There are thousands of stars in the night sky in this range, with half visible at any time (unlike the incorrect claims about Starlink satellites where relatively little of the constellation has line of sight at any given moment.) The motion would further increase the brightness required to cause saturation.

I've seen first hand statements from LSST people that they are very concerned and have done significant analysis. They are modifying their observing strategy and even the camera readout to try to mitigate it. The observing strategy is something that's been subject to years of debate and optimization, so it's likely that science will suffer, even if they manage to meet the baseline goals. It also depends a lot on how many of the constellations get built, what orbits they end up on, and how bright they end up being.

So in other words, while no one ever claimed the impact would be 0, there is currently not enough basis to be certain that the impacts would not be negligible.

I also know first hand that other surveys like Super-ASASSN are significantly affected. NEO searches are also likely to be heavily affected, since they necessarily need to look relatively close to the sun. Some statements from Pan-STARRS
https://www.mauinews.com/news/local-news/2019/06/more-satellites-in-space-streak-mar-telescope-images/

I mentioned NEOs already, if you have a comment on them you can look at my previous post first. Your comment about Super-ASASSN being "significantly affected" is simply worthless at this point as you have not provided any definition for significant. We are well past the point in the conversation where you should have any illusion that I will accept vague assertions without data.

Another is you arguing against the point of moving all ground spaced astronomy to space in the near term, which again would just be you trying to force an idiotic strawman argument into my mouth.

That "strawman" is literally the subject of the thread "Can telescopes in space replace ground based telescopes? ", and common refrain of the people who claim Starlink won't be a problem, including Musk himself in his initial reaction.

The OP says nothing about it being done in the near term, and clearly clarified with questions about which types of research are able to be done on the ground versus in space. A partial answer to the questions is that there is no research that needs to be done on the ground, although for now there is a significant amount that is cheaper to do on the ground. (The inverse is not true as there are some wavelengths essentially unusable from the ground.) A fairly obvious corollary to the OP's questions that was quickly brought up is what it would take in the near term to offset near term impacts from satellite constellations. The first step to answering that requires determining how significant or not the impacts are to begin with.

I recognize you aren't making the argument that we can just put everything in space. I think your assumptions about how cheap lift will affect the cost of doing astronomy in space are extremely optimistic, but I'll freely admit the uncertainties are large.

And here I agree with you in a sense. There is adequate room for disagreement on how much Starship may lower in-space astronomy costs, as the data simply does not exist yet to be certain. However a 10x factor compared to a ground based telescope is what you would expect in today's market, not a future one with cheap launch as assumed by the OP. personally I think that pretty much no one is prepared for the impacts of Starship, and if it meets half of what it is supposed to in double the time frame, somewhere between few and no one will be ready to fully leverage it.

[redliox]

If you could rebuild ground telescopes on the Moon, the lunar versus terrestrial telescopes would give science less obstructed by an atmosphere.  The advantage terrestrial telescopes have, and likely will have for decades if not centuries to come, is all the staff and replacement parts are down here on Earth.  It's a superior view versus superior support is what it comes down to.

Personally, I believe sooner rather than later a time's coming where ground telescopes will produce less science than space ones (lunar or orbital-based).  However, there are still numerous "tricks" ground 'scopes still have that'll make them worthwhile for a decent while yet.  The shift, when it happens, likely will come with the higher wavelengths first (gamma to UV) since those are the most disturbed by the atmosphere while you can still gain some optical, infrared, and radio science on the ground.

[Rebel44]

If you could rebuild ground telescopes on the Moon, the lunar versus terrestrial telescopes would give science less obstructed by an atmosphere.  The advantage terrestrial telescopes have, and likely will have for decades if not centuries to come, is all the staff and replacement parts are down here on Earth.  It's a superior view versus superior support is what it comes down to.

IMO, it would massively help the cost as well as reliability if we stopped building telescope parts that are unique for every telescope and instead switch to standardized modular construction. Cheap access to space and modular architecture would also make replacing faulty parts much easier/cheaper (so we wouldn't need to spend so much time and money testing and checking every part).

[hop]

You apparently did not understand my question at all, you had asserted that the value of observing time is different depending on season to cancel out that impacts from seasons where there is more of a problem or less of a problem cancels out.

I think you misunderstood the answer. I didn't claim that the value of the observing time changed with the season. How long the satellites are visible after twilight changes with the season (and observatory latitude). Since the dark time is more useful for astronomy, the seasonal effects don't cancel out. But this is a minor point. The main point is that common refrain of "you only see them around twilight" is simply not accurate as a general statement.

See Patrick Seitzer's presentation that envy887 posted for how this works out near the LSST site. Higher latitudes suffer more.

"Some observations" my next question should be obvious: what specific observations?

I'm not going to review the whole field for you. It's a simple, obvious fact that people take data when they think they can get useful data, and this varies widely depending on the instrument and target. People trying to cover the whole sky use as much of the night as they practically can. People observing dynamic phenomena don't get to choose when their targets are observable. 2I/Borisov is a recent high-profile example where the immediate post-discovery observations pushed the limits.

I have significant questions about what they used as inputs to the analysis, because "nearly every" does not seem like a plausible result. At the least this probably ignores the mitigations mentioned in your previously provided links. The statement you quoted does not clarify how much of the 2 hours is actually useful to begin with, and the next sentence almost seems to contradict it with statements about 40% (or less) of twilight observing time impacted. The statements about saturation in the link in particular are questionable since Starlink sats in operation should be +4 to +7 magnitude There are thousands of stars in the night sky in this range, with half visible at any time (unlike the incorrect claims about Starlink satellites where relatively little of the constellation has line of sight at any given moment.) The motion would further increase the brightness required to cause saturation.

If you think your off-the-cuff reaction is more likely to be right than analysis by people responsible for one the flagship astronomy programs of the decade, you're welcome to that opinion. I would however suggest the LSST team are aware of the existence of bright stars and the fact satellites move, so you might want step back and think about which analysis is more likely to be lacking sufficient detail.

As I mentioned earlier, years have been spent debating, simulating and optimizing LSST observing strategy. It's a topic the community takes seriously and is well equipped to analyze. See https://github.com/LSSTScienceCollaborations/ObservingStrategy for starters. Many more papers can be found on arxiv.

I'm honestly baffled by your reaction here. You don't have to follow astronomy very closely to know that many professional astronomers are deeply concerned by the impacts of these mega-constellations. It isn't news or controversial among people who actually do this stuff.

[meberbs]

I think you misunderstood the answer. I didn't claim that the value of the observing time changed with the season. How long the satellites are visible after twilight changes with the season (and observatory latitude). Since the dark time is more useful for astronomy, the seasonal effects don't cancel out. But this is a minor point. The main point is that common refrain of "you only see them around twilight" is simply not accurate as a general statement.

See Patrick Seitzer's presentation that envy887 posted for how this works out near the LSST site. Higher latitudes suffer more.

Here is what I originally had to say on seasons:

When you think about the geometry, you need to include inclination and seasons.

If you think about the seasons, you see that it is better for half the year and worse for half the year. This doesn't really change anything.

At this point everything you just stated supports my point. Your counterargument that "value of the time at the extremes isn't equal" is something you still have failed to explain. And again, you jump back to making it sound like I am trying to defend a different point which is both wrong and not something I had stated.

I'm not going to review the whole field for you. It's a simple, obvious fact that people take data when they think they can get useful data, and this varies widely depending on the instrument and target. People trying to cover the whole sky use as much of the night as they practically can. People observing dynamic phenomena don't get to choose when their targets are observable. 2I/Borisov is a recent high-profile example where the immediate post-discovery observations pushed the limits.

Astronomy is a field of science. Quantifying things like the impacts of  is what is expected. Anecdotes are less important than hard data and specifics. If the impacts are really as bad as certain social and news media seem to imply, there should be scientific papers documenting that.

I have significant questions about what they used as inputs to the analysis...

If you think your off-the-cuff reaction is more likely to be right than analysis by people responsible for one the flagship astronomy programs of the decade, you're welcome to that opinion. I would however suggest the LSST team are aware of the existence of bright stars and the fact satellites move, so you might want step back and think about which analysis is more likely to be lacking sufficient detail.

I specifically said that I questioned the assumptions they used as their inputs. They did not specify things like exactly how many satellites in what orbital planes, or assumptions about brightness. They did not even give results about whether saturation would occur. I also pointed out that 2 of the stats they gave seem contradictory at a glance. Right now their analysis has not been provided in the detail to judge these things.

You mentioned Patrick Seitzer's analysis above. I have looked at that, and it shows the 550 km altitude only impacts for about 1 hour after twilight, and even multiplied by 10 for number visible for a final state, does not seem consistent with the claims on the LSST site you linked. The LSST claims are based on "full deployment" but the meaning of that is not clear, did they use the 10s of thousands that SpaceX filed with the ITU with no defined orbital parameters? Most of SpaceX's future plans with defined orbits are for VLEO satellites even lower than current deployments. LSST's release states 200 satellites visible at any one time. Seitzer's worst case with 1500 sats at 1150 km shows a bit over 20 visible near twilight, multiply number of sats by 10, and you would get around 200 only for parts of the night. This is both an exaggeration of altitude and an assumption of more satellites than SpaceX has explicit plans for (should be closer to 11k than 15k).

I have expressed no opinion related to my off the cuff reaction being more valid than their analysis, I have just requested more detail on their inputs, since at first glance it does not seem consistent with other analysis that does specify exactly what orbits it is assuming.

As I mentioned earlier, years have been spent debating, simulating and optimizing LSST observing strategy. It's a topic the community takes seriously and is well equipped to analyze. See https://github.com/LSSTScienceCollaborations/ObservingStrategy for starters. Many more papers can be found on arxiv.

The only thing this says for sure is that it will take analysis from experts to actually determine the significance of impacts.

I'm honestly baffled by your reaction here. You don't have to follow astronomy very closely to know that many professional astronomers are deeply concerned by the impacts of these mega-constellations. It isn't news or controversial among people who actually do this stuff.

I am baffled by your hostile reactions to simple requests for data. You don't have to follow this very closely to see that plenty of people are making a lot of noise without data to back it up. (For example, check this post where someone realized they had been supporting a significant misrepresentation of the impact of Starlink on the night sky.)

[envy887]

You apparently did not understand my question at all, you had asserted that the value of observing time is different depending on season to cancel out that impacts from seasons where there is more of a problem or less of a problem cancels out.

I think you misunderstood the answer. I didn't claim that the value of the observing time changed with the season. How long the satellites are visible after twilight changes with the season (and observatory latitude). Since the dark time is more useful for astronomy, the seasonal effects don't cancel out. But this is a minor point. The main point is that common refrain of "you only see them around twilight" is simply not accurate as a general statement.

See Patrick Seitzer's presentation that envy887 posted for how this works out near the LSST site. Higher latitudes suffer more.

"you only see them around twilight" is pretty much exactly what Seitzer's presentation was showing. In general, the number of satellites visible at a given time before twilight is double the number visible the same time after twilight, and within ~1 hour after evening twilight, and up to 1 hour before morning twilight, that number generally goes to zero. At least at CTIO-ish latitudes.

This behavior is independent of the total number of satellites, but does strongly depend on their orbital altitude, with lower satellites being much brighter, but also much quicker to lose illumination around twilight.

Unfortunately for inner solar system observations, the last satellites to lose illumination in the evening, and the first ones to re-illuminate in morning, are probably near the the ecliptic and low to the horizon, which is also where those observations tend to need clear skies.

[hop]

"you only see them around twilight" is pretty much exactly what Seitzer's presentation was showing. In general, the number of satellites visible at a given time before twilight is double the number visible the same time after twilight, and within ~1 hour after evening twilight, and up to 1 hour before morning twilight, that number generally goes to zero. At least at CTIO-ish latitudes.

Note the red bars are astronomical twilight (which is well past the everyday use of the term), meaning everything in between would normally be prime observing time. So yeah, for a broad value of "around" it's true (edit: at ~30 deg latitude), but it does not mean the impact is negligible. In practical terms it means a couple hours per night are affected.

Things are much worse at higher latitudes, as the map on that wiki page should make clear.

[envy887]

"you only see them around twilight" is pretty much exactly what Seitzer's presentation was showing. In general, the number of satellites visible at a given time before twilight is double the number visible the same time after twilight, and within ~1 hour after evening twilight, and up to 1 hour before morning twilight, that number generally goes to zero. At least at CTIO-ish latitudes.

Note the red bars are astronomical twilight (which is well past the everyday use of the term), meaning everything in between would normally be prime observing time. So yeah, for a broad value of "around" it's true (edit: at ~30 deg latitude), but it does not mean the impact is negligible. In practical terms it means a couple hours per night are affected.

Things are much worse at higher latitudes, as the map on that wiki page should make clear.

The impact on observing time near twilight is not negligible, but the impact for the large majority of the night is zero.

CTIO is at 31 degrees. All of the world's 6+ meter optical telescopes and 90% of the 3.5+ meter optical telescopes are within 35 degrees of the equator, largely for the same reasons that Starlinks will be less visible there... twilight is shorter, and summer nights are longer.

[jbenton]

We will need an Elon Musk for space telescopes... 

There have been some intriguing ideas for decreasing the costs of space telescopes coming down the pipeline.

1) NASA and a company called Lightweight Telescopes, Inc. started this project:
https://www.nasa.gov/feature/goddard/2016/nasa-eyes-first-ever-carbon-nanotube-mirrors-for-cubesat-telescope
They've developed a way to impregnate an epoxy resin with carbon nanotubes, pour it into a mold for the correct shape, and then put a thin metallic film over it (after it hardens). This process is much faster and cheaper than the conventional method and allows for easy mass production.
The current prototypes are only 3 inches (~7.62cm) across and are intended for CubeSats, though apparently they could be scaled up to larger 'scopes, eventually. The researchers believe that this technology will be especially useful for segmented mirrors. Given what I've read in the article, it seems that these would be pretty useful for Ground-based observatories as well.

Of course it's not just the mirrors. The mirror for WFIRST was donated to NASA free of charge, and the spacecraft will still cost >= $3.2 billion - not including launch costs. (Though the mirror itself is estimated to be worth $250 million - which is over $1 million per cm in diameter). Building large sats in general is really expensive. The new carbon nanotube mirrors are lighter than their predecessors, but they still require significant bulk to carry.

2) "Orbiting Rainbows":
https://www.nasa.gov/jpl/tech/glitter-cloud-may-serve-as-space-mirror
This idea is to use lasers to maneuver strips of metal into a telescope mirror like formation. The resulting picture is very "noisy" but according to tests, existing computer technology is sufficient to clean it up. Theoretically a spacecraft could fly that is smaller than the mirror it uses with this technique. Radio telescopes are easier to make this way than visual light ones. However according to this article:
https://www.npr.org/2014/12/23/372468028/could-glitter-help-solve-nasas-giant-telescope-problem
this project is decades away from producing anything on a large scale.

[OTV Booster]

No, unfortunately meberbs that entire thread is two or three people arguing the same points back and forth. It's mostly quieted down now, so it's safe to skim it, but there hasn't been a whole lot more math than pointing out that the math used to fearmonger was kind of bogus.

Thanks, that is what I thought, I had looked at the thread some. (And I admit to being one of the 2 or 3 people in certain other threads (usually new physics) that ended up similar, so I get how that happens.)

It has been long enough that if a specific astronomy mission was going to have major irrevocable impacts, someone probably would have quantified them by now, and knowing this site, someone would find that quickly. In my mind, the lack of such a report puts a loose bound on how severe the impacts can get. I expect one will eventually get published one way or another to guide future missions.

Working my way up thread so apologies if I hammer a nail already driven.

Let’s look at what would go into a calculation starting with only one sat of some arbitrary angular size and one telescope with some arbitrary angular resolution. WARNING: my math sucks but I do have a reasonably good grasp of what the calculations need to represent.

If the sat angular dimension is less than the scopes resolution, and the sat is ‘dark’ there is no problem - sometimes. If the sat occultates (passes in front of) a star under observation the light curve will change and trigger questions. If the sat is bright it’s a different set of problems.

Some observations are extended objects such as nebula and galaxies. Bright and dim sats have effects roughly the same as above.

Then there is the question of the chances of this happening. Here we move away from one sat and one telescope. How many sats and how many scopes? It’s not just starlinks at one angular size. Many different sats of different sizes and altitudes and many many more coming. Many scopes of different capabilities. Some nailing one target at a time some doing survey work.

In short, a deep and hairy question. Any calculation would have so many assumption built in it would only be an easily demolished target for anybody who didn't like the answer.

So, the only answer I can come up with is tomorrow there will be ‘some’ impact on astronomy and the day after tomorrow there will be ‘more.’

I am a life long amateur astronomer. Amateur and professional both bemoan light pollution. Professionals bemoan RF pollution. Seismologist bemoan things that rumble. Things aren’t the way they used to be...

It will piss off a lot of people. People will adapt. They are currently building the third generation of scopes within my lifetime. One reason they are so expensive is the few locations with both no light pollution and acceptable atmospherics. By definition the are built out in the boonies.

The generation currently abuilding will probably have truncated lifetimes and a higher operating cost:discovery ratio than desired in part due to having to work space traffic into the observing runs. As the cost of operations goes up and the cost of space flight goes down, the following generation of scopes will move to the new boonies: space.

It won’t be a forklift move. Onesie twosie.  Forty years down the road astronomers will nostalgically admire all the old hardware (I still get a rush from an old scope with a brass tube) but shake their heads at even thinking of using it for productive work.

Phil

Edit to add: wow, talking about a nail already driven.  Children, behave!

[envy887]

Suppose, hypothetically, we wanted to replace LSST's wide-fast-deep capabilities with an in-space constellation, and that launch costs are in the $100/kg range?

What would this constellation look like? What is the cost-optimal:

1) size for each observatory?

2) number of satellites in the constellation?

3) orbit for surveying (considering accessibility, viewing area/time, and data return)?

With a constellation, it should be possible in theory to trade light collecting area for longer exposures, making up the the lost speed by having more scopes with smaller fields of view to get a fast revisit rate.

[OTV Booster]

Suppose, hypothetically, we wanted to replace LSST's wide-fast-deep capabilities with an in-space constellation, and that launch costs are in the $100/kg range?

What would this constellation look like? What is the cost-optimal:

1) size for each observatory?

2) number of satellites in the constellation?

3) orbit for surveying (considering accessibility, viewing area/time, and data return)?

With a constellation, it should be possible in theory to trade light collecting area for longer exposures, making up the the lost speed by having more scopes with smaller fields of view to get a fast revisit rate.

Classic answer: it depends.

I did a long windy reply and on reread I realized I’d not quite hit your question. But because I’m as much in love with my own word as the next guy I’ll leave it be.

On a re reread I think I did answer it but from my own weird angle.

Here goes:

First question is where would you put it?

LEO has thermal issues, a planet in the way half the time and perturbations from the moon and masscons. E-M L1 2 &3 are better but still are less than ideal. L 4&5 have some promise if there isn’t too much junk already there.

E-sun Lagrange points might be a very stable position but my guess is sun-Jupiter L1 could be really good. I’m not sure exactly how far in that is. If it gets too close to Mars that might be a deal breaker.

With interferometry two mirrors of any size spaced such that their outer edges are as far apart as a large mirrors diameter will have the same resolution as the large collector but not the light gathering ability.

Let’s look at this for S-J L1. Assuming Mars isn’t a problem there is a strong advantage in cryo cooling working very well. Especially if observations are always far from the sun. A combo PV/sunshade will get the temp down real nice. Next there will be minimal differential thermal effects inducing vibration.

A light weight CF truss could hold the sub mirrors at 8.4m (LSST) or 10m or ... 

One thing I am not clear on. More mirrors can be added to the truss to increase light gathering. I do not know if they must be part of the interferometry setup or if they can add useful data without. Either way is doable. Just a question of complexity.

The truss can be simple, a large ‘X’ or even a pie pan covered with mirrors.

And yes, because this is, at least in theory, super stable, very long exposures will go deeper on point sources. It’s a little trickier on extended objects. Planets, exoplanets, resolvable stars and nebula will behave differently - I think.

The problem here is that if the gathering surface (a couple small mirrors) is small compared to the aperture (distance between them) not only is the image dimmer but the contrast is also lower for extended objects.  This is argument for filling in with a lot of mirrors.

A note on extended objects and contrast.  This is my semi informed take on it. It is what I understand from years of reading but I’ve never focused on it and could be wrong. I’ll probably consult the oracle later and put out a Yup or Mia Culpa.

If I’ve got all this right what it boils down to is, just as all the engineering/customer desires/money trade offs that went into LSST resulted in a particular design and set of capabilities, doing it again in a space environment will not result in an exact duplicate. If LSST capabilities are a target you’ll either get something better in some way and worse in others, or you’ll spend much more for incremental gains.

Phil

[OTV Booster]

While I was doing the pervious post I remembered a space telescope design I noodled a long while back.

Take a ring of arbitrary diameter and a few cm thickness. Glue a sheet of Mylar or other suitable material to either side. Mildly pressurize the then enclosed space.

Edit to ad: do this in space.

The two sheets will bulge into catenaries. Spray the backs with something that will set up hard. Aluminize the interior surfaces and you are the proud owner of two fine mirrors.

An amateur telescope maker rule of thumb is that a mirror ground to F/16 or longer need not be configured from spherical to parabolic. I would venture that this is true for visual work and the f ratio would have to go up significantly with modern instrumentation.

The difference between a catenary and a parabola is much smaller than sphere and parabola. There is probably some f ratio where the difference is beyond significance. For faster systems the mildest of corrector lens would do.

If this can be robotized, the optics and the transportation of the optics gets less expensive. Same for station keeping props and reaction wheels or CMB’s for aiming.

If E. Musk has his way (go Elon!) we are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history rewoven with a fresh pattern. (Damn, did I just say that?)

Envy, I think this is a better reply to your question and maybe to the question this this thread poses.

Phil

[envy887]

LSST isn't trying to resolve anything, AFAIK. It's just gathering light. So there's no point in interferometry, and if you can run longer exposures, then there's no need for the huge mirror. Using smaller mirrors and building more of them gives a double helping of cost savings.

Also, ISTM the problem with deep space orbits for a survey constellation is getting all the data back. DSN is slow and already too busy. I think a TESS-like elliptical orbit where download happens near perigee at high data rates solves this nicely.

[Swedish chef]

Take a ring of arbitrary diameter and a few cm thickness. Glue a sheet of Mylar or other suitable material to either side. Mildly pressurize the then enclosed space.

I'm somewhat fond of this idea, to get rid of the expensive and heavy main mirror and launch or perhaps fabricate something of lesser quality, then when that not so ideal mirror is in space use adaptive optics to straighten it out. If you can bend a perfectly ground mirror out shape to overcome the trouble of atmosphere here on earth I'm guessing the same thing could be used in space on a mirror of lesser quality.

Now the adaptive optics on a telescope here on earth are constantly moving to adjust for the atmospheric effects, my suggestion would only have to be actuated once, or every few days to overcome heat issues deforming the main mirror. (I would probably try the adaptive optics on the secondary mirror since they need something sturdy and therefore heavy and expensive to act upon)

Might this work or is there they usual problem of garbage in, garbage out?

[OTV Booster]

LSST isn't trying to resolve anything, AFAIK. It's just gathering light. So there's no point in interferometry, and if you can run longer exposures, then there's no need for the huge mirror. Using smaller mirrors and building more of them gives a double helping of cost savings.

Also, ISTM the problem with deep space orbits for a survey constellation is getting all the data back. DSN is slow and already too busy. I think a TESS-like elliptical orbit where download happens near perigee at high data rates solves this nicely.

I’m not sure one way or the other on the interferometry. The resolution is seeing limited at .7”. Not sure what diameter is needed to get this in the optical range.

Wikipedia has a good overview of both the optics and the data handling. The data flow is incredible. They are budgeting for ONLY 1.28 petabytes/year because there will be down time for maintenance and weather. I don’t know the breakdown on that.

There is nothing out there now or in the foreseeable future that can handle a data pipe that big. That’s where making projections through the disjunction comes in.

In the 10 or 15 years (did you see me wave my arms <g>?) it will take for the next generation of space scopes to show up it’s impossible to know what sort of space coms will be available. Whatever it is, the coming revolution in access to space means we can not do a linear projection.

Future comms could range from a solar system wide StarLink on steroids to something wacky like a signal carrying laser pumping a spot on Jupiter or the suns corona for observation from earth. Don’t spend too much time shooting down that last. It’s a place holder for ‘something completely new that we’ve never thought of.’

The StarLinks that will degrade surface observation will contribute to the revolution that will allow observations we can only dream of now.

Here’s a standing bet: within the next 20 years we will be able to image the Alpha Centauri system in the optical range at the same resolution the 200” can give at Jupiter, and it will be done from space. I’d cut that down to 15 years but predictions are hard, especially if they’re about the future.

Phil

Edit to add: I’d make the bet a beer but if I’m still around in 20 years my doctor probably won’t let me drink it. 

[OTV Booster]

Take a ring of arbitrary diameter and a few cm thickness. Glue a sheet of Mylar or other suitable material to either side. Mildly pressurize the then enclosed space.

I'm somewhat fond of this idea, to get rid of the expensive and heavy main mirror and launch or perhaps fabricate something of lesser quality, then when that not so ideal mirror is in space use adaptive optics to straighten it out. If you can bend a perfectly ground mirror out shape to overcome the trouble of atmosphere here on earth I'm guessing the same thing could be used in space on a mirror of lesser quality.

Now the adaptive optics on a telescope here on earth are constantly moving to adjust for the atmospheric effects, my suggestion would only have to be actuated once, or every few days to overcome heat issues deforming the main mirror. (I would probably try the adaptive optics on the secondary mirror since they need something sturdy and therefore heavy and expensive to act upon)

Might this work or is there they usual problem of garbage in, garbage out?

Adaptive optics are heavy and take a fair amount of power by satellite standards. ISTM that any curvature problems can be dealt with through corrective optics.

Mylar has a great level of smoothness but it’s probably not a fraction of a wavelength. Maybe another material or maybe a microgravity manufacturing technique can fix this.

Any thermal distortion is best handled by avoiding it in the first place. That’s why my first instinct was to station far out and do a stand off heat shield.

It may be that innovative space built mirrors will not be of inferior quality. Once launch becomes relatively inexpensive and infrastructure is built up the scope itself may become much less expensive per meter of aperture with no loss of quality. It will be exciting to watch.

Adaptive optics also work to adjust mirror sag with changing angle. Another problem that goes away with space based scopes.

Phil

[Zed_Noir]

<snip>
Also, ISTM the problem with deep space orbits for a survey constellation is getting all the data back. DSN is slow and already too busy. I think a TESS-like elliptical orbit where download happens near perigee at high data rates solves this nicely.

A wacky idea about transferring survey data back from a deep space location.

Packed a large unmanned space vehicle with a few hundred tonnes of SSDs along with a short range laser communication system to retrieved the data in the vicinity of a constellation data nexus.

There could be a relay of SDD packed data retrieval vehicles to retrieved the data periodically from each nexus.

Of course a few hundred tonnes of high capacity SSDs will not be cheap for even a single data retrieval vehicle. Think you need at least a handful of such vehicles.

[OTV Booster]

<snip>
Also, ISTM the problem with deep space orbits for a survey constellation is getting all the data back. DSN is slow and already too busy. I think a TESS-like elliptical orbit where download happens near perigee at high data rates solves this nicely.

A wacky idea about transferring survey data back from a deep space location.

Packed a large unmanned space vehicle with a few hundred tonnes of SSDs along with a short range laser communication system to retrieved the data in the vicinity of a constellation data nexus.

There could be a relay of SDD packed data retrieval vehicles to retrieved the data periodically from each nexus.

Of course a few hundred tonnes of high capacity SSDs will not be cheap for even a single data retrieval vehicle. Think you need at least a handful of such vehicles.

Woo Hoo. Someone as wacky as me and braver about it too.

I was thinking about a passel of thumb drives brought back my cube sats. Treat each cubesat like a RAID drive and if you miss one, de nada.

The investigators will go nutso waiting for the pipeline to fill.

Phil

[OTV Booster]

<snip>
Also, ISTM the problem with deep space orbits for a survey constellation is getting all the data back. DSN is slow and already too busy. I think a TESS-like elliptical orbit where download happens near perigee at high data rates solves this nicely.

A wacky idea about transferring survey data back from a deep space location.

Packed a large unmanned space vehicle with a few hundred tonnes of SSDs along with a short range laser communication system to retrieved the data in the vicinity of a constellation data nexus.

There could be a relay of SDD packed data retrieval vehicles to retrieved the data periodically from each nexus.

Of course a few hundred tonnes of high capacity SSDs will not be cheap for even a single data retrieval vehicle. Think you need at least a handful of such vehicles.

On a more serious note looking ~15 years down the road we can expect a more robust space comm infrastructure.

DSN will be far surpassed. Here comes the hand waving.

StarLink and it’s competitors will have the capacity to link to anything below GEO. GEO will have ability to link to anything cislunar including L1 halo and Earth-Sun L4&5 which in turn can link to E-S L1. These in turn will be able to link to Mars- Sun L4&5... etc.

That’s probably overkill for solid uninterrupted comms between Earth, Luna and Mars but you get the idea. Comms for an ongoing investigation beyond Mars will need a commitment for an extension of the comms infrastructure or it won’t be feasible.

Using current technology the bandwidth would be inadequate. Extrapolating for 15 years is dicy but my guess is some subset of Moore’s law applies. Far UV or X-ray lasers come to mind along with all the multiplexing and phasing games that comes with multiple channels.

It really is impossible to extrapolate 15 years. My guess is that if space infrastructure does not progress to something along these lines (capability, not specific architecture) in 15 years it will be a sign that Musk’s plan to get all the eggs out of one basket is too little, too late. Mars will never thrive if it’s a communications backwater.

Phil


Edit: changed a couple L2’s to L1’s.

[hop]

A wacky idea about transferring survey data back from a deep space location.

Packed a large unmanned space vehicle with a few hundred tonnes of SSDs along with a short range laser communication system to retrieved the data in the vicinity of a constellation data nexus.

Note that near real-time alerts for transients is a major objective for LSST (see https://www.lsst.org/about/dm/data-products).

AFAIK expected overall data volume from is on the order of ~20TB/night. Not impossible to do from space, but definitely a substantial challenge compared to current missions, especially outside of LEO.

[Robotbeat]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

The cost could actually be *lower* due in part to lower gravity.

Large ground observatories are super expensive. Keck has to be constantly refrigerated to near-freezing during the day so that it's at the same temperature as at night (so as not to distort the telescope). They're enormous objects that need to be precisely pointed.

In space, you don't need a laser guide star. You're not perturbed by day, by clouds, by the Moon, etc. That means you probably have 3 times the observing time. You can observe in any direction. You can observe (fairly) close to the sun.

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

So I actually think you COULD replace ground telescopes with space-based ones.

The smaller scopes would also be needed.

But we need not just cheap launch, but cheap human workers in orbit.

[OTV Booster]

I doubt there is anything that must be done on the ground, but even if launch is free, the cost of reconstructing humanity's collective ground-based capabilities in space would be, er, astronomical.

The cost could actually be *lower* due in part to lower gravity.

Large ground observatories are super expensive. Keck has to be constantly refrigerated to near-freezing during the day so that it's at the same temperature as at night (so as not to distort the telescope). They're enormous objects that need to be precisely pointed.

In space, you don't need a laser guide star. You're not perturbed by day, by clouds, by the Moon, etc. That means you probably have 3 times the observing time. You can observe in any direction. You can observe (fairly) close to the sun.

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

So I actually think you COULD replace ground telescopes with space-based ones.

The smaller scopes would also be needed.

But we need not just cheap launch, but cheap human workers in orbit.

An advantage you missed is the optics would be refraction limited rather than atmospherically limited. For he cost of the time needed to collect more photons, a small scope can do the same job as a large scope.

The cost of human workers is less wages (as I’m sure you realize) than the cost of maintaining infrastructure. As launch costs drop, infrastructure costs drops. The meat bags can pull in $1m/year each and it’s not even a rounding error until launch costs drop to something ridiculous.

Phil

[Proponent]

The cost could actually be *lower* due in part to lower gravity.

Large ground observatories are super expensive. Keck has to be constantly refrigerated to near-freezing during the day so that it's at the same temperature as at night (so as not to distort the telescope). They're enormous objects that need to be precisely pointed.

In space, you don't need a laser guide star. You're not perturbed by day, by clouds, by the Moon, etc. That means you probably have 3 times the observing time. You can observe in any direction. You can observe (fairly) close to the sun.

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

The 39-m ELT has a price tag of about a €1.2 billion euros.  Allowing for some cost growth, that's perhaps one-fifth the cost of the 5.6-m JWST.  JWST employs robotic systems for deploying both mirror and sunshade, but I've never found in the GAO's reports any indication that those systems drive the bulk of the cost (I've looked, because advocates of Ares V and SLS used to claim that JWST would be much cheaper if only its mirror did not require deployment).  JWST's optical tolerances are looser, because it's optimized for the infrared, yet still it's mirror is made of beryllium, for thermal reasons.  I'm pretty sure refrigeration of large ground-based telescopes is far cheaper than JWST's method of refrigeration, namely sending it to Earth L2, with a whopping huge sunshade.

EDIT:  JWST's requirements for cooling are much more stringent than those for ELT, since JWST operates well into the infrared.  Hence, the comparison is not fair.

[su27k]

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

Is this just back of envelope guesstimate, or has this been studied?

I do hope NASA does some study on this subject, given we may have the launch capability for this in the near future.

[trm14]

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

Is this just back of envelope guesstimate, or has this been studied?

I do hope NASA does some study on this subject, given we may have the launch capability for this in the near future.

Yeah, I'd like to see some source for that, too. It sounds quite dubious to me.

[OTV Booster]

To assembly a 14m reflector assembly only takes about a 5 hour EVA for a couple astronauts. We could just build a whole bunch of large aperture telescopes in orbit. One crew could build dozens of them in a single 6 month stint. And the weight is lower than deployable structures. Much lower hardware cost, too.

Is this just back of envelope guesstimate, or has this been studied?

I do hope NASA does some study on this subject, given we may have the launch capability for this in the near future.

Five hours - maybe after getting a few under their belt. This would not include alignment and collimation. If it’s a segmented mirror this could be a slow job. Automated actuators could speed this up but add a lot of mass. They could be part of a tool kit and one set used for multiple mirrors.


Making the machine is hard. Making the machine that makes the machine is really hard. It would boil down to production numbers.


Phil

[eeergo]

Another data point:

https://twitter.com/jaynebirkby/status/1699410725184123149

GMT: 10x Hubble res, 4x JWST res, $2B-class project, NET 2029, decades of continuously upgreadable observations
LUVOIR (proposed): 5x JWST res, $10B-class project, NET 2039, 5-10 years of primary+extended mission

Ratio LUVOIR/GMT: 1.25x resolution, 5x cost, similar (?) development periods, substantially longer operations

[Robotbeat]

It will take a completely different approach to make space telescopes competitive. It’s possible, but it has definitely not yet been done. No one has taken an extremely cost-aggressive approach like Starlink for space telescopes.

(I do not mean to imply you’d use distributed satellites… monolithic has a lot of advantages. Secondly, Starlink has a massive commercial market whereas space telescopes don’t really.)

That said, a factor of 5 difference in cost is much smaller than I expected!

A space telescope can operate for 2-4 times as often (not limited by weather or daylight or seeing conditions), and it can see targets in both hemispheres without problem. It also has full spectrum capability.

[eeergo]

It will take a completely different approach to make space telescopes competitive. It’s possible, but it has definitely not yet been done. No one has taken an extremely cost-aggressive approach like Starlink for space telescopes.

(I do not mean to imply you’d use distributed satellites… monolithic has a lot of advantages. Secondly, Starlink has a massive commercial market whereas space telescopes don’t really.)

That said, a factor of 5 difference in cost is much smaller than I expected!

A space telescope can operate for 2-4 times as often (not limited by weather or daylight or seeing conditions), and it can see targets in both hemispheres without problem. It also has full spectrum capability.

Of course, $10B is the minimally credible budget that can be quoted after JWST - it's likely it will end up costing significantly more, just like JWST was supposed to be $1B in its infancy. Probably not such an extreme overrun in percentage ($0.1T is hardly justifiable) but still. The estimated running cost for those 10 years of ops, by the way, is between $8-14B, or around $1B/year. I didn't quote it because I couldn't find such a figure for GMT, but I'm fairly certain it won't be close to even the same order of magnitude, not even including upgrades or accounting for the extra observing time available.

[Robotbeat]

JWST was massively mismanaged. No one will believe it now that it has successfully launched, but JWST should’ve been canceled a decade or two ago. Its successful launch, normalizing this borderline corrupt incompetence by contractors (and dishonesty by the proposers, who knew it’d cost VASTLY more than they claimed), is a Pyrrhic victory.

[eeergo]

JWST was massively mismanaged. No one will believe it now that it has successfully launched, but JWST should’ve been canceled a decade or two ago. Its successful launch, normalizing this borderline corrupt incompetence by contractors (and dishonesty by the proposers, who knew it’d cost VASTLY more than they claimed), is a Pyrrhic victory.

Mostly every major innovative project in spaceflight (and outside of it, to be honest) should have been cancelled by that metric. Not trying to redeem the incompetence and dishonesty that I agree was avoidable, but it was hardly a one-off, except perhaps for the absolute and relative sizes of the overrun. That's why I made the caveat nobody should expect a 10x cost increase for LUVOIR, but neither the cost estimate made decades before its launch when it's just a concept. The GMT budget has much less play in it, if only because first light is expected in about 5 years and construction is well underway.

[Robotbeat]

Lots of projects were managed far, far better. Kepler, the Mars Exploration Rovers, etc. The most insidious idea is that the mismanagement doesn’t matter because “it costs what it costs.”

[joek]

Mostly every major innovative project in spaceflight (and outside of it, to be honest) should have been cancelled by that metric.

What "metric" are you referring to? Plenty of programs ("innovative" and otherwise) have been cancelled.

Not trying to redeem the incompetence and dishonesty that I agree was avoidable, but it was hardly a one-off...

But you are.

JWST was a mismanaged disaster by any measure. Let's all hope it was a "one-off". Excusing it is imply accepting the normalization of deviance.

[eeergo]

Mostly every major innovative project in spaceflight (and outside of it, to be honest) should have been cancelled by that metric.

What "metric" are you referring to? Plenty of programs ("innovative" and otherwise) have been cancelled.

Not trying to redeem the incompetence and dishonesty that I agree was avoidable, but it was hardly a one-off...

But you are.

JWST was a mismanaged disaster by any measure. Let's all hope it was a "one-off". Excusing it is imply accepting the normalization of deviance.

You're engaging in both a false equivalence and a non-sequitur at the same time, while skirting ad-hominems with your tone, and explicitly deleting the on-topic point in my post. Congrats.

False equivalence: Cancellations having existed (or projects respecting budgets) does not imply there are plenty of important-to-egregious overruns whose continuation vs cancellation was justified a posteriori, just like JWST has been doing since launch. The most glaring example is ISS, without which the commercialization of LEO would most likely not have happened, international cooperation would have been stymied even further, and earlier, than current affairs have taken it, HSF would most likely have suffered a decade-long, if not more, gap in flights, etc. It was close to cancellation both during construction on the ground, on-orbit assembly and the early utilization phase.

Likewise, most HSF projects were close to cancellation at some point in their tenure, with rabid proponents of such measures: from Apollo (before and just after Apollo XI, and finally dramatically after Apollo XVII) to STS (throughout its lifetime) to SLS.

Beyond HSF, Hubble was as close to cancellation as JWST, including after its on-orbit incident after launch, and throughout its life due to (IMHO) shortsighted beancounting regarding STS servicing missions.

Most "Flagship" missions in NASA, ESA and other agencies had similar trajectories. WFIRST/Nancy-Roman has had to deal with such talk since the NRO mirros were unveiled, even though its cost increase has -for now, crossing fingers- been modest. Ditto for MSR. Cassini was under the sword of Damocles several times, as was MSL/Curiosity, GLAST, Suomi/NPOESS-PP, Glory, Europa Clipper is still feeling the breeze left over by its latest swoop... Internationally, ExoMars, Athena, Cluster, SOHO...

Outside of spaceflight, many transportation (both vehicles and civil engineering) and scientific projects suffer similar trends. A notable project that WAS cancelled and led to very bad outcomes for the community and related neighboring fields, far exceeding the cost savings, was the infamous SSC accelerator.

Most of these have in common that they were doing something unprecedented, as opposed to valuable yet more technically run-of-the-mill missions like the mentioned Kepler. The MERs were a virtuous exception in this field.

Non-sequitur: I explicitly said JWST's mismanagement is not redeemable, and that it was avoidable. No, the philosophy shouldn't be "it costs what it costs" barring specific, very well justified exceptions. Yet without much discussion to back it, you just call my qualifiers (nothing is black or white, especially in light of the above) "excuses", ignore the challenges associated with extremely innovative projects that push the state of the art forward, and mix in the ominous "normalization of deviance" in a context far from where it was coined.

[joek]

...

Said what I had to say about JWST long ago in other threads. Plenty of "backstory" if you've read those threads and the references. Simply put, JWST was a disaster. Let's not try and sugar coat it.

[JulesVerneATV]

Astro Brief: Lunar Radio Telescope
https://www.ksmu.org/show/astro-brief/2025-08-21/astro-brief-lunar-radio-telescope

[floss]

Build a 2 km optical telescope beside the radio telecom and we will be able to see the planet's around other stars .

[JulesVerneATV]

NASA's Hubble Space Telescope and Chandra X-ray Observatory joined forces to find an elusive intermediate mass black holes
https://www.yahoo.com/news/videos/hubble-spots-nearly-impossible-intermediate-190000812.html

A tiny detector could unveil gravitational waves we’ve never seen before
https://www.sciencedaily.com/releases/2025/10/251003033920.htm

DECi-hertz Interferometer Gravitational wave Observatory (or DECIGO) similar to cancelled LISA, is a proposed Japanese space-based gravitational wave observatory, LISA is supported by the ESA and expected to have a Launch date 2035,  .
https://web.archive.org/web/20230201204235/https://dcc.ligo.org/public/0038/G060318/000/G060318-00.pdf
Japan design is similar to LISA, with four zero-drag satellite clusters (two colocated) in a triangular arrangement, but using a smaller separation of only 1000 km

Hubble Space Telescope watches dying star chow down on a Pluto-like world filled with ice
https://www.space.com/astronomy/hubble-space-telescope/hubble-space-telescope-watches-dying-star-chow-down-on-a-pluto-like-world-filled-with-ice


Some estimate Starship can be ~$90 million but maybe as high as 200 million until costs drop

another US Private company New Glenn might also be there offering cheap payloads or a commercial company from China or India, the Russians are currently under sanctions after the Ukraine invasion. Titan IV was retired in 2005, ESA Ariane is falling behind with others going reusable, Germany and PLD Space are trying commercial.  Shuttle payload to LEO was approximately $54,500 per kg, The Shuttle derived SLS is another system for large payloads but perhaps too expensive. Since Elon Musk'sspace missions launching objects into low-Earth orbit has come down by "a factor of 20."

Musk's Space-X is on the 11th flight but still no payload to orbit

SpaceX completes 11th test flight of its Starship rocket
https://www.nbcnews.com/science/space/spacex-completes-starship-rocket-test-flight-rcna237463

[Hobbes-22]

DECi-hertz Interferometer Gravitational wave Observatory (or DECIGO) similar to cancelled LISA, is a proposed Japanese space-based gravitational wave observatory, LISA is supported by the ESA and expected to have a Launch date 2035,  .

Cancelled? Are you sure you intended to write that?

[JulesVerneATV]

Cancelled?

Sorry badly worded,  the various ideas for Gravity Wave observatories are on Earth and in outer space are complementary rather than competitive. LISA is alive and it has not been the only one to see troubles and cuts over the years https://web.archive.org/web/20110604121537/http://www.astrobio.net/exclusive/4005/rage-against-the-dying-of-the-light 2011 news on SIM and TPF

They discussed a joint mission between ESA and NASA in 1997, then NASA withdrew, 2008, 2009 cuts, back in for more science more cuts in 2016 then NASA joins again and usually missions that require "recovery actions" end up adding a lot to the overall budget and now more rumors of 'threats' but all is ok.

June, 2025 news

'European Space Agency reveals 3 key space missions threatened by Trump's NASA budget cuts'
https://www.space.com/space-exploration/european-space-agency-reveals-3-key-european-space-missions-threatened-by-trumps-nasa-budget-cuts

Venus orbiter EnVision also mentioned and largest X-ray observatory ever planned, 'NewAthena' so not just talk about 'LISA'

Lisa-pathfinder mission has already flown and that cost was 490 million 'Euros'
https://www.space.com/33094-lisa-pathfinder-gravitational-wave-tech-demonstration-results.html
the mission ended in 2017

2035 LISA launch date remained unchanged.
https://www.esa.int/Science_Exploration/Space_Science/LISA/Construction_of_ESA_s_ambitious_LISA_mission_begins

[ralfvandebergh]

Frankly, personally I don't like the premise of this reasoning. This is, of course, from an industrial perspective, a businessman's reasoning, which is understandable. No hate here. A better question would be: Is it worth filling the sky with satellites only for improved internet communication? Astrophotographers already have to use tricks to remove the many satellite trails from their photos just to take a nice picture, let alone professional astronomers with their scientific work. And with all the competing companies, this is just the beginning. Of course, you could argue that these are also celestial objects and belong there. But that's not the point here. Don't get me wrong, I'm even a satellite photographer; I just photograph almost exclusively satellites.

Then there's the telescope industry and the people who work on the ground in observatories, operators and (maintenance) technicians for instance. They'll lose their jobs too, right?

And to go slightly off-topic, I haven't even mentioned the environmental impact of all these launches, not to mention the subsequent atmospheric burn-ups of so many satellites. And what about the increased collision risks? Look, we have to take some responsibility, we can't just keep launching and assume all this has no impact on our environment. That's like a child in a toy store. I'm a rocket enthusiast too, but we also have to be willing to take responsibility. Of course, launches will always continue to increase in the era we live in, and I think that's great, but let's work hard on more environmentally friendly emissions and other solutions.

Mars really should be a backup location; we shouldn't go there because it has become uninhabitable on Earth.

Ralf Vandebergh

"Astronomers should be happy about SpaceX. Cheap access to space will enable a lot of space telescopes, no worries about mega constellations disturbing ground based astronomy"


This is one of the most common answers one can read when talking about effects of starlink and other satellite constellations on ground based telescopes. Even from people like Everday Astronaut or Elon Musk himself. My feeling is that this is not a very realistic argument but I want to learn more about it and hear some thoughtfull opinions on this topic?

Let's say Starship will be flying soon and it will actually be very very cheap. Can you really replace ground based telescopes? What types of research/wavelengths could be done in space? And what types of research need to be done on the ground and why?

[ralfvandebergh]

Comet picture with Starlink trails example:

https://www.reddit.com/r/astrophotography/comments/1oskm10/comet_lemon_and_satellites/

Frankly, I don't like the premise of this reasoning. This is, of course, from an industrial perspective, a businessman's reasoning, which is understandable. No hate here. A better question would be: Is it worth filling the sky with satellites for improved internet communication? Astrophotographers already have to use tricks to remove the many satellite trails from their photos just to take a nice picture, let alone professional astronomers with their scientific work. And with all the competing companies, this is just the beginning. Of course, you could argue that these are also celestial objects and belong there. But that's not the point here. Don't get me wrong, I'm even a satellite photographer; I just photograph almost exclusively satellites.

Then there's the telescope industry and the people who work on the ground in observatories. They'll lose their jobs too, right?

And I haven't even mentioned the environmental impact of all these launches, not to mention the subsequent atmospheric burn-ups of so many satellites. Look, we have to take some responsibility, we can't just keep launching and assume all this has no impact on our environment. That's like a child in a toy store. I'm a rocket enthusiast too, but we also have to be willing to take responsibility. Of course, launches will always continue to increase in the era we live in, and I think that's great, but let's work hard on more environmentally friendly emissions and other solutions.

Mars really should be a backup location; we shouldn't go there because it has become uninhabitable on Earth.

Ralf Vandebergh

"Astronomers should be happy about SpaceX. Cheap access to space will enable a lot of space telescopes, no worries about mega constellations disturbing ground based astronomy"


This is one of the most common answers one can read when talking about effects of starlink and other satellite constellations on ground based telescopes. Even from people like Everday Astronaut or Elon Musk himself. My feeling is that this is not a very realistic argument but I want to learn more about it and hear some thoughtfull opinions on this topic?

Let's say Starship will be flying soon and it will actually be very very cheap. Can you really replace ground based telescopes? What types of research/wavelengths could be done in space? And what types of research need to be done on the ground and why?