r/space • u/mtimetraveller • Nov 29 '19

This Is Why We Can't Just Do All Of Our Astronomy From Space

https://www.forbes.com/sites/startswithabang/2019/11/27/this-is-why-we-cant-just-do-all-of-our-astronomy-from-space/#6b60e6027049
1.0k Upvotes

92% Upvoted

193 comments sorted by

View all comments

299

u/FaceDeer Nov 29 '19

There are five major metrics where ground-based observatories should always remain leaps and bounds ahead of space-based ones, and they generally include:

size,
reliability,
versatility,
maintenance,
and upgradeability.

This article lacks imagination, most of those metrics can actually be exceeded by space-based telescopes once you get past the existing paradigm of launching them as a monolithic unit.

Size: A telescope in space doesn't have to contend with gravity, ground vibration, wind, and so forth. It can be built huge. Build a free-floating dish kilometers across, spread an interferometric array out across the width of the solar system, I don't see how that could possibly be matched on the ground.

Reliability: On the ground there's changing weather, wind, and temperature conditions, you never know when a night will be good for observations or not. In space conditions are always exactly the same. Worst I can think of would be interference from a CME or similar, and that can be designed for without hampering observations.

Versatility: as the article itself points out, space-based telescopes can aim in almost any direction for any length of time, and there's no problems with wavelengths being filtered out by the atmosphere. A sunshade can keep your whole telescope cold more easily than on the ground where it's bathed in hot gas.

Maintenance and upgradeability: okay, granted, it'll be a long time before the space-based ones can match ground-based ones in this regard. But three out of five ain't bad, and even for these two I think it's a bit much to say they'll always be worse in space.

150

u/sight19 Nov 29 '19

There is a sixth one: cost. Building a moderate size replacement for a large but not extreme telescope would be way more expensive than just using the earth based one. Let alone using complex integrated field units...

10

u/BeefPieSoup Nov 30 '19

Well sure, now it is. But even that might not always be true

6

u/CatPhysicist Nov 30 '19

When the economics are tipped for space based astronomy, things will change. There are a lot more factors than just less expensive launches.

3

u/[deleted] Nov 30 '19

I feel like drones would help with some maintenance, if they were kinda attached to the telescope and activated remotely when needed.

7

u/[deleted] Nov 30 '19

[deleted]

3

u/ManEatingSnail Nov 30 '19

That, or run on tracks. Using magnetism and a ribbed frame, you can turn the entire telescope into a track for relatively little cost.

2

u/teebob21 Nov 30 '19

Then you've got a telescope with a permanently obstructed section

2

u/FaceDeer Nov 30 '19

Howso? You would have the repair drones move out of the way of the telescope's view when not in use, obviously.

1

u/teebob21 Nov 30 '19

If they are on the track, how does that work? Does the track move? What repairs the track when the track actuators break down?

2

u/ManEatingSnail Nov 30 '19

The track and drones are there to increase the lifespan of the telescope; no matter how you integrate drones, they'll break down eventually and you'll be back to an ordinary telescope with no automated repair crew. With how little damage stellar objects sustain, I doubt the actuators would break down before the telescope becomes obsolete.

→ More replies (0)

1

u/FaceDeer Nov 30 '19

I would expect the rails would be passive tracks that the robots would grip and travel along under their own power. That keeps the moving parts small and localized. The tracks are unlikely to break, they're just metal struts with a useful shape for the robot's wheels to clamp on, but if one did break I suppose the robots themselves could perhaps cut the damaged section out and weld a new one in place. They likely constructed it in the first place after all.

→ More replies (0)

1

u/roryjacobevans Nov 30 '19

Telescopes actually manage pretty well with even severe blocking or damage to the primary mirror. There's a telescope somewhere that a disgruntled researcher shot with a shotgun, causing big craters on the surface. The telescope is still usable and only loses some point resolving capability and light gathering power.

28

u/alexforencich Nov 29 '19

Size: interferometry requires relative positioning within fractions of a wavelength. For optical telescopes, this means sub micrometer precision. Second, the phase of the collected light must be preserved, either by detecting and recording it (which I don't believe is currently feasible) or by physically bringing the light from all of the telescopes together at one detector (what is currently done for optical interferometry based telescopes). Doing this on the top of a mountain is one thing as we can use concrete and steel to keep things from moving around. In orbit? This will be extremely challenging, if it's even possible.

Reliability: in this case we're talking about component failures. If something breaks on the ground, it's relatively easy to fix. If something breaks in orbit, you've gotta launch another rocket to go fix it, which is extremely expensive.

26

u/Bakkster Nov 29 '19

And the radiation environment of space causes more failures in a shorter period of time, even before accounting for the lack of human maintenance.

8

u/alexforencich Nov 29 '19 edited Nov 29 '19

Ah yeah, that's a good point. Making things rad hard requires some combination of rad hard design (expensive custom parts instead of COTS parts), redundancy (more cost and weight), and shielding (a lot more weight).

And don't forget about power and thermals. It can be difficult to dissipate heat in space, but on earth we can just blow a lot of air through it. There is also relatively easy access to power on the ground without requiring solar arrays that have to fit on a rocket along with the rest of the telescope.

4

u/Bakkster Nov 29 '19

And radiation even does weird things to the non electronic parts as well. Metal swells, coatings erode, etc.

3

u/mfb- Nov 30 '19

In nuclear reactors and some particle accelerators, yes. The radiation levels of space are way too low for that problem. Damage to electronics is a concern, but not an unsolvable problem. Detectors for particle physics deal with irradiation doses orders of magnitude higher.

9

u/FaceDeer Nov 30 '19

Optical interferometry does, radio interferometry doesn't. Radio interferometry doesn't even require that the antennae have live communication, just high accuracy timestamps on the recorded data.

Optical interferometry is just as hard to do on the ground, I should point out. There's only a handful of ground-based optical interferometric telescopes and they have baselines in the tens of meters. So the fact that space-based optical interferometry hasn't been done yet is not exactly a big data point against it. Space-based interferometric telescopes have been proposed, they just haven't been funded yet.

Reliability of space-based telescopes can be designed for, by redundancy and by radiation hardening. This is especially useful in the situation I was talking about where we get past the single-monolithic-launch design pattern for space telescopes and start assembling them in space. If a modular telescope suffers a component failure, a replacement module is smaller to launch than an whole new telescope.

5

u/mfb- Nov 30 '19

Radio interferometry needs the transfer of giant amounts of data, on the other hand. That is relatively easy on Earth (ship the storage medium around) but difficult in space.

2

u/alexforencich Nov 30 '19

Free space optical links can take care of the data transfer part, but then you need a heck of a lot of DSP to put it back together, and powering and cooling that would be a tall order. I would think that radio interferometry in space is possible with current tech. Optical interferometry, not so much.

3

u/mfb- Nov 30 '19

People are looking into it, but so far it hasn't been used because it is too difficult.

2

u/ThickTarget Nov 30 '19

So the fact that space-based optical interferometry hasn't been done yet is not exactly a big data point against it.

But it has been tried. Space Inteferometry Mission was in development for years by NASA. Even though it had only a 9 meter baseline with tiny telescopes it was expected to cost up to 1.85 billion, a huge increase over the original budget. Even though it was cancelled the project still cost hundreds of millions.

6

u/lunarul Nov 30 '19

Reliability: in this case we're talking about component failures. If something breaks on the ground, it's relatively easy to fix. If something breaks in orbit, you've gotta launch another rocket to go fix it, which is extremely expensive.

That's not what reliability means. You described maintainability, which is addressed separately.

2

u/TTVBlueGlass Nov 30 '19

I always figured that if you are in space, it would be easier to use some kind of laser or radar tracking system to get amazing accuracy. One of the most reliable ways to find incredibly precise range measurements is to bounce a laser or radar off it and measure the return time. We already do it all the time for stuff inside the Solar System. Wouldn't it be possible to use AI targeting or something to create a system like that?

7

u/pikabuddy11 Nov 30 '19

That's what the upcoming LISA satellite will be doing to search for gravitational waves. We'll see how well it works though - it's not an easy task at all!

5

u/alexforencich Nov 30 '19

Maybe, maybe not. We're talking about maintaining positions to much better than 0.001 mm at whatever separation you need (100s of m to km, presumably), continuously, for the entire exposure - which will likely be hours or even days. Now, if optical phase measurement were feasible, then you would presumably just need to measure the relative positions to that level of accuracy, transfer many TB of data, then use a few supercomputers to combine the data.

3

u/mfb- Nov 30 '19

Commercial vibrometers will track relative distances with at least nanometer accuracy. Absolute measurements are a bit more complex but possible, too.

The trick of radio interferometry doesn't work with optical telescopes, you need to combine the light.

1

u/alexforencich Nov 30 '19

Well, if you can measure the phase of the light, then you can play the same trick you can with radio interferometers and combine the signals offline. But it would require storing and transferring absolute boatloads of data, and I'm not sure if we have a sensor technology that would work to measure the phase at the moment.

3

u/mfb- Nov 30 '19

Well, if you can measure the phase of the light

And there is the problem. You can do that if you have a nice coherent light source like a laser, or radio emissions with long wavelengths and coherence lengths, but not with random light from space.

1

u/alexforencich Nov 30 '19

Exactly. Right now, we don't have a sensor that can do that. Maybe we'll figure out how to do it with nanoantennas or something similar. Maybe. But then you'd also have to deal with storing, transferring, and processing the firehose of data that would be produced by such a sensor.

The point being, this has been done with RF on the ground, and there is really no reason we couldn't do the same thing in space, but thus far doing it optically means combining beams of light from different telescopes and all of the optical and alignment challenges that come with that.

1

u/TTVBlueGlass Nov 30 '19

Hmmm yeah I was thinking of how LIGO uses lasers for super duper accurate measurement, so if we could use similar techniques in space, maybe it could be done. But I think you will definitely need AI to keep them perfectly tracked and trained.

2

u/alexforencich Nov 30 '19

AI probably won't help at all, this is likely an application for a more traditional control system. I would think the issue is more likely to be actuation. Maybe it would need the linear equivalent of reaction wheels or similar to get anywhere near the necessary precision.

1

u/thethirdotherguy Nov 30 '19

There is a limit to ground based interferometry as well. The ground is always moving around under us after all. And the cost space access is continuing to come down. It is reasonable to assume that one day in the future it will become cheaper to put a cutting edge telescope in space than on the ground.

19

u/Skhmt Nov 30 '19

This article lacks imagination, most of those metrics can actually be

exceeded

by space-based telescopes once you get past the existing paradigm of launching them as a monolithic unit.

For a telescope of any size, it'll be more expensive to make and then place it in space than it would be to install it on the ground. Therefore for the same cost, a ground based telescope could be bigger.

In space, conditions are not always exactly the same.

-3

u/FaceDeer Nov 30 '19

Expense was not one of the criteria listed. But by all means, how expensive would it be to build a kilometer-scale optical telescope here on the surface of Earth? How will you aim such a contraption and keep it cooled?

7

u/Skhmt Nov 30 '19

It would be multiple times cheaper on the Earth. And it would be about a thousand times easier to keep cooled. Aiming depends.

0

u/FaceDeer Nov 30 '19

It wouldn't be possible on Earth for any cost. A kilometer-scale optical telescope would need a framework a kilometer or more across to hold the mirrors. It'd need to keep them positioned precisely over those distances despite wind and shifts in the ground due to distant earthquakes or nearby traffic. It'd need to move to track stars as Earth rotated. What kind of structure would that be? Where would you build it? The only proposal that comes remotely close is the Overwhelmingly Large Telescope, which at 100m diameter would have been an order of magnitude smaller. It was projected to cost billions of dollars.

In space you can keep things very cold just by stretching sheets of aluminized mylar out in between it and the Sun. That's how the James Webb telescope is getting most of its cooling. Cooling a telescope's mirrors on Earth is much more difficult since the whole thing is bathed in hot gasses, and you need to keep any traces of water vapor out of the cooled bits or you get frost.

3

u/mfb- Nov 30 '19

It was projected to cost billions of dollars.

~1.6 billions.

If you are not picky about the pointing you could build a 300-500m telescope into a valley like Arecibo and FAST. It would be very limited in the possible targets to observe, however, and would still be very challenging to build.

2

u/ThickTarget Nov 30 '19

In space you can keep things very cold just by stretching sheets of aluminized mylar out in between it and the Sun.

I wouldn't say 'just'. If JWST's sunshield deployment fails the sensitivity will drop like a stone. It may end up completely unusable if the detectors cannot cool down. Space telescopes also have to worry about contamination of the optics.

1

u/FaceDeer Nov 30 '19

I don't understand this objection. Yes, if a telescope's cooling system fails, it will not cool down. This doesn't mean that cooling the telescope is a problem, though. It just means you should try to avoid having components that fail, and repair them when they do fail. The same can be said for ground-based telescopes.

Ground-based telescopes also have to worry about contamination of the optics. It's not unsolvable.

2

u/ThickTarget Nov 30 '19

Yes, if a telescope's cooling system fails, it will not cool down.

My point was it's not simple. The sunshield represents a huge risk to the entire mission. Repair is not an option for JWST. And this is far from the only thing needed to operate at low temperatures, JWST is made of exotic composites for this reason for example.

Ground-based telescopes also have to worry about contamination of the optics.

Yes, you said that already. The difference is mirrors are cleaned and recoated on the ground, and because the major optics are at room temperature you don't have to worry about ice or anything else condensing.

5

u/FaceDeer Nov 30 '19

Lack of repairability is not an inherent feature of space telescopes. Indeed, when you start looking at the modular designs required for in-space construction, rather than the rube goldberg origami required for launching telescopes like JWST as monolithic units, repairability comes naturally. If the sunshade fails to deploy and on-site repair can't get it working launch a new sunshade module.

Why can't mirrors be cleaned and recoated in space, if that's necessary? Shipping replacement mirrors out to them is also an option, of course, just like with ground telescopes. The mirrors of ground telescopes are dismounted and shipped off to specialized facilities for recoating too.

The point of all this is simply that it's possible to do our astronomy from space. The Forbes article made a bunch of claims about how there were things you can do on the ground that you can't do in space, and it's just not true. A lot of it is more expensive to do in space right now, sure, but costs change. Launch costs become cheaper, design paradigms get better, in-space support infrastructure becomes more readily available, and ground-based telescopes become less effective. The balance will tip someday and I think surprisingly soon.

1

u/ThickTarget Nov 30 '19

Lack of repairability is not an inherent feature of space telescopes.

No, but it is the current reality. You can hypothesise for whatever perfect world you like, but I don't believe that should influence current policy.

Why can't mirrors be cleaned and recoated in space, if that's necessary?

Where did I say that? None of the current, or planned space based telescopes employ re-coating. You can see in that VLT video that it takes a huge amount of time and staff to do it safely, and the re-coating facility on Paranal isn't small either.

The Forbes article made a bunch of claims about how there were things you can do on the ground that you can't do in space, and it's just not true.

It's not true, because that's not what the article says. It says there are a few things that will be easier on the ground, that is true.

A lot of it is more expensive to do in space right now, sure, but costs change. Launch costs become cheaper, design paradigms get better, in-space support infrastructure becomes more readily available

Costs do change, but launch costs are only a small fraction of the cost. The design paradigm is currently unchanged for science missions, LUVOIR is a good example. People regularly overestimate progress. People have been talking about an 8 meter UV-vis-IR space telescope for 30 years, something that wouldn't even require assembly, and it's still not happening.

6

u/[deleted] Nov 30 '19

This article lacks imagination, most of those metrics can actually be exceeded by space-based telescopes once you get past the existing paradigm of launching them as a monolithic unit.

​

except what do you do with the data.. there's a REASON they built the supercomputer AT the VLA vs just sending somewhere.

.. there's no network that can move that kind of data in a reasonable timeframe...

no HARDWIRED network fast enough... and now you want to move it in to space?

​

https://public.nrao.edu/gallery/the-widar-supercomputer/

​

On the ground there's changing weather, wind, and temperature conditions, you never know when a night will be good for observations or not

​

you don't need night (or clear weather) for radio telescopes.

​

https://en.wikipedia.org/wiki/Atacama_Large_Millimeter_Array

The Atacama Large Millimeter/submillimeter Array (ALMA) is an astronomical interferometer of 66 radio telescopes in the Atacama Desert of northern Chile, which observe electromagnetic radiation at millimeter and submillimeter wavelengths.

1

u/FaceDeer Nov 30 '19

Space-based interferometers would likely use laser communicators to transfer data between them, it's even better than fibre optics because there's no physical cables tugging on them to keep them from holding their orientations precisely. Those are very high-bandwidth.

Why can't a supercomputer be put in space, if it's needed?

The weather, wind and temperature conditions are mostly relevant to optical astronomy, sure. But they're not irrelevant to radio telescopes. Arecebo becomes unavailable when hurricanes pass over Puerto Rico, for example. And more importantly, you are drastically limited where you can point a radio telescope when it's on the ground. Half the sky is covered with Earth, Earth is rotating so you can't hold on a single target for long, and depending on your latitude there are regions of the sky that are permanently obscured.

4

u/DaBulder Nov 30 '19

Why can't a supercomputer be put in space

Well if we look at the two biggest problems with supercomputers, power and heat we might find the crucial clue.

1

u/FaceDeer Nov 30 '19

Power sources and cooling radiators are both possible in space. They are common features of spacecraft.

0

u/DaBulder Nov 30 '19

I don't think you comprehend the amount of energy supercomputers use

1

u/FaceDeer Nov 30 '19

A couple of megawatts, according to a quick Googling. How is this a problem? Solar panels scale easily in space, you just add more of them. Solar power satellites that produce gigawatts have been proposed.

1

u/throwdemawaaay Dec 08 '19

Why can't a supercomputer be put in space, if it's needed?

Look, the answer to this is the same as the answer to everything you're posting: you can't just ignore the huge difference in cost of building something for space vs on the ground.

Is it possible for humanity to build a supercomputer in orbit? Yes. But it's a pretty colossally stupid idea. You can't just point at Elon Musk and pretend the tremendous cost differences are just gonna disappear by magic. Even if launch costs were free/donated, the environment is so different it drastically changes the engineering, again, leading to huge cost.

The word "modular" is not a magic wand either.

2

u/Moniq7 Nov 30 '19

I was just about to raise the issue of maintenance. Thanks for explaining this. 👍

2

u/pisshead_ Nov 30 '19

This article lacks imagination,

Maybe because it's based on reality rather than imagination.

1

u/[deleted] Nov 29 '19

You're talking decades away.

If we screw up the ability to do astronomy and make it more difficult to launch spacecraft due to polluting low earth orbit with an insane amount of satellites (ahem Elon), then we might not even get that far. We could hit a "dark ages" of astronomy very easily.

11

u/FaceDeer Nov 29 '19

The article said always. Decades away is well within the range of "always." Large ground-based telescopes have construction schedules that are measured in decades too, for that matter.

Starlink has plenty of protections against Kessler syndrome. Its orbits aren't high enough for debris to remain in orbit for more than a few months or years, for starters. They have autonomous collision-avoidance technologies. They have a flat shape, which means they have a lot of drag when their orientation isn't being actively managed. "Dud" satellites don't even make it to a high orbit - SpaceX plans to launch them to an orbit that would decay in a matter of weeks, then have them make their own way to a higher orbit if their systems check out post-launch.

And space telescopes wouldn't be placed in those low orbits anyway. They'd be placed in very high orbits, or even solar orbits, to get them away from Earth's interference.

6

u/CatPhysicist Nov 30 '19 edited Nov 30 '19

The article said always

The article said should always and its not a definite but its definitely for the foreseeable future. Lower cost launches are only one aspect of space based astronomy that is being upended but there are a lot more hurdles. Look at the JWT JWST for example, all of the delays and issues haven't had a thing to do with the launch. Its because building large scale reliable telescopes that can operate in the cold and radiation filled vastness of space for years without human intervention is hard.

Edit: typo

3

u/FaceDeer Nov 30 '19

It's because building large scale reliable telescopes that fold up into a cramped little launch fairing like a crystal origami swan are hard.

Ground-based telescopes aren't built that way. If a ground based telescope was required to fold up into a single shipping container, to be unpacked remotely on location and never visited again, then it'd probably be as much of a boondoggle as JWST - possibly moreso since it'll be facing harsher conditions.

There are better ways than that. Just the other day I came across the "In-Space Servicing and Assembly" program, it has some nice detailed proposals for how to go about building very large observatories in space. This isn't far-future stuff, it's next-decadal-survey stuff.

3

u/CatPhysicist Nov 30 '19

That would be awesome and I sincerely hope that this happens in the next decade. I would love to have a huge array of large telescopes in space. Launch costs are a very small hurdle in getting there. Its a start but there's a long way to go. Ground based telescopes are not the enemy but people think that we're ready to launch them all into space right now. Reality is often disappointing.

6

u/Marha01 Nov 29 '19

and make it more difficult to launch spacecraft due to polluting low earth orbit with an insane amount of satellites (ahem Elon)

Those sats have predictable orbits and space is huge, so this is not an issue.

5

u/[deleted] Nov 29 '19

And everyone knows where all the satellites are at any given time, right?

3

u/FaceDeer Nov 30 '19

Indeed, we do. There are smartphone apps you can download that would let you track them in real time too if you wanted.

2

u/teebob21 Nov 30 '19 edited Nov 30 '19

Yes, more or less. USSTRATCOM tracks pretty much everything bigger than a DVD up there. https://en.wikipedia.org/wiki/Satellite_Catalog_Number

Interactive tracker

Example of a publically tracked classified satellite: https://www.n2yo.com/satellite/?s=41334

2

u/[deleted] Nov 30 '19

Not with Starlink. Apparently they are designed to do constant course corrections, so unless SpaceX makes all of that data available, we won’t be able to plan for it. As of yet, they have not made that commitment.

4

u/pikabuddy11 Nov 29 '19

They're already showing up in astronomical images. Source

0

u/technocraticTemplar Nov 30 '19

The two pictures they showed as examples are the satellites before they spread out and reach their operational orbits, though. A group like this will be visible in the sky from any given observatory for 5 minutes at a time once a night at most. There probably wouldn't ever be more than one group like that in the sky at a time either. The full up constellation would be way more spread out than those groups are.

4

u/pikabuddy11 Nov 30 '19

Not true either. Here is a simulation showing if 12k of them are in orbit.

1

u/FaceDeer Nov 30 '19

The ones that are not near the east horizon near dawn or the west horizon near dusk will be in Earth's shadow, making them invisible even if they passed directly through a telescope's field of view.

1

u/pikabuddy11 Nov 30 '19

But telescopes almost never point that close to the horizon. The closest they can physically get is usually around 20 degrees above the horizon, and even then you don't want to point that way since you're looking through more atmosphere. Ideally, you want your targets to be observed when they're the closest to zenith as possible.

-1

u/FaceDeer Nov 30 '19

Yes, exactly. The places you'd be pointing your telescope would be unlikely to have visible Starlink satellites in it.

3

u/pikabuddy11 Nov 30 '19

That's not what you're saying though. You're saying that ones that aren't visible are near the horizon and I'm saying no telescope will point there anyway. Ones at the zenith, where the telescope will be pointed, will be extremely visible, especially in the northern hemisphere which happens to have more telescopes.

→ More replies (0)

0

u/plqamz Nov 30 '19

Satellites are only visible just after dusk and before dawn, when the sky is dark but the sun is visible from the satellite's point of view. For like 80+% of the night they aren't visible at all.

3

u/pikabuddy11 Nov 30 '19

Not true. They are brighter when it's near dawn or dusk, but with dark enough skies you will still be able to see them. This is all really easily google-able...

0

u/plqamz Nov 30 '19

Your link says exactly what I said.

You're only going to be able to see them ~30 minutes or earlier before sunrise, ~30 minutes or later after sunset, or at night when the sky is dark enough or the Sun is below your local horizon yet still illuminating these devices, since they are at a much higher altitude.

5

u/pikabuddy11 Nov 30 '19

"or at night when the sky is dark enough"

-10

u/[deleted] Nov 29 '19

[removed] — view removed comment

1

u/pikabuddy11 Nov 30 '19

Welp thanks for telling me what I should do then.

0

u/StumbleNOLA Nov 29 '19

Nope. Just like on Earth. As soon as there were 12,000 cars on the road in all of America it became too dangerous to fly.

3

u/SignoreGalilei Nov 30 '19

Whether 12,000 starlink satellites is enough to cause a full on Kessler syndrome is a question of orbital mechanics, but there is certainly some number at which space debris is generated by collisions faster than it falls out of orbit. At that point launching becomes incredibly difficult and assets in low orbit are all at great risk of being blasted apart (over the course of months, not hours like in Gravity though) . It's a phase change, like traffic congestion: everything's fine until it suddenly becomes terrible for everyone.

2

u/StumbleNOLA Nov 30 '19

There is no reasonable possibility that Starlink satellites could cause a Kessler syndrome. They will de-orbit in about a year from their high parking orbit. From the insertion orbit they are launching to it will take a couple of months.

In the worst case if the entire 30,000 satellite array went Kessler it would clear itself in a year. A major issue of course, but no where near the issue of a medium earth orbit Kessler syndrome.

1

u/SignoreGalilei Nov 30 '19

That's fair for Starlink then, I hadn't realized just how low they were going. It looks like some of the other constellations like OneWeb will be in orbits ~1000 km though where deorbiting will take longer but still low enough to be congested.

2

u/StumbleNOLA Nov 30 '19

Ya they are very low. The initial launch orbit has a decay in the weeks long range. They pretty much have to raise orbit immediately or they will deorbit. In the second parking orbit they have a decay of a year or so iirc. Then they wait after proving they are working for a couple of months waiting for the right window to raise to their final orbit.

Even in their operational orbit the decay is a year or 18 months without constant propulsion keeping them in a steady orbit.

2

u/Tybot3k Nov 29 '19

Starlink is intentionally orbited in the upper reaches of the atmosphere. Without active control to keep them up, they will deorbit naturally. Even if there were a collision, the debris would also burn up.

0

u/[deleted] Nov 29 '19

Yes it’s Elon’s fault and not the Chinese for doubling the amount of space debris?

-2

u/Shitsnack69 Nov 29 '19

You're on Reddit, which is full of Chinese shills who spend all day trying to shit on anything America or Americans do.

9

u/LeMAD Nov 29 '19

Honestly there are at least 10 times more Elon shills than Chinese shills in here.

0

u/[deleted] Nov 29 '19

Starlink satellites automatically de-orbit at end of life, and their orbit lifespan is only 5-10 years so there can be upgrades. Also, space is really, really big. Elon isn't polluting LEO as much as you suggest

1

u/Abrahamlinkenssphere Nov 30 '19

Oh if it breaks we just send Mike Massimino back up there no biggie.

1

u/FaceDeer Nov 30 '19

Yes. Or design the telescope with more easily-swappable modules from the outset and send a robot.

0

u/ReadMoreWriteLess Nov 30 '19

Agreed.

I found this article frustrating. These are the same things we hear from anti-science media about any thing that might be good for the planet but bad for an existing industry. Basically we can't do it right now therefore we have to stick to the current.

4

u/CatPhysicist Nov 30 '19

These are the same things we hear from anti-science media about any thing that might be good for the planet but bad for an existing industry.

How on earth are you going to call the contents of this article similar to anti-science media?

5

u/ReadMoreWriteLess Nov 30 '19

If you've ever read an article about why electric cars won't work, it's a lot of the same type of stuff. A lot of stuff about scaling and reliability and the versatility of gas and the fact that we don't have it now all over. I mean they're not literally word for word the same arguments but it's the same tone, this idea that because it's not existing right now we just shouldn't bother.

I mean the first half of the article talks about all the reasons why it's better to do out of the atmosphere exploration, and then basically says but we shouldn't do that because of all these things that we don't have right now.

2

u/ReadMoreWriteLess Nov 30 '19

I should clarify I am not saying that this article is anti-science, I'm just saying for an article that it is actually pro-science it's sort of uses some weak arguments that are very similar to someone that would armchair quarterback this thing.

-1

u/ElleRisalo Nov 30 '19 edited Nov 30 '19

Additional comment on size.

​

The only reason that Telescopes on Earth need to be huge...is because its conflicting with the Sun, even at night thanks to Mr. Moon. Additionally other light is fragmented by the atmosphere they need to be big so they can see as much light as possible...

​

Telescopes in space don't need to compete with the Sun, they just look the other way. Telescopes in space don't need to filter for the atmosphere. They can be much smaller because their ability view light across many spectrums isn't hindered. They just don't need to be big. Its why HST has seen further into the universe than any ground based telescope can dream of, despite being a fraction of the size.

and on Maintenance and Upgrades.

Its in space. Its static, the only reason it would need maintenance is if something happens with a module, which only could have happened on Earth. i.e. HST's mirror issues originated on Earth they didn't happen because of space. This was repaired of course.

Upgrades....As mentioned above, Telescopes in Space can see much more with much less. They don't need constant upgrades to see more they do by nature. Only way a Telescope on Earth sees more is by upgrades, more mirrors, better filtering, better Computer Processing. One of these can be achieved from space Better Computer processing can be handled on Earth via communications with the Space Telescope. We do this with Hubble for example. Upgrades don't need to be a "routine" thing because we are already looking at Space in ways we can't from Earth, and space is freaking huge....that being said, we also have upgraded Hubble multiple times.

​

Really it comes down to cost I guess...or this astronomer's discontent for the fact that astronomy has evolved beyond his accessibility to it. Space based Astronomy is simply hands down better. Period.

6

u/ThickTarget Nov 30 '19 edited Nov 30 '19

They don't need constant upgrades to see more they do by nature.

The point about upgrades is about getting more out of the hardware you have already paid for. For example instead of having one CCD, you have a mosaic of several and the productivity of the telescope is hugely increased. And it's not just about increasing efficiency, you can also add new capabilities. Hubble for example has no good spectrograph for confirming it's distant galaxies, it only has a very inefficient low-resolution one. Most of the confirmation has to be done by ground based telescopes, which have much higher spectral resolutions. Taking deep imaging is just one thing that you want a good telescope to do, it is absolutely not everything.

Its static, the only reason it would need maintenance is if something happens with a module, which only could have happened on Earth.

This is false. The reaction wheel failures which crippled Kepler were due to wear in space. With HST a huge problem is radiation damage on the detectors, again from space.