Cat GIFs obvs. And why isn’t there one in the article?
Swarms of small communications satellites saturating space may make it more difficult to observe and track potentially hazardous asteroids zooming toward Earth, astronomers have warned. A report [PDF] out this week compiled by the Satellite Constellations 1 (SATCON1) committee outlined the repercussions of the growing number …
Cat GIFs just aren't the same since Grumpy Cat died.
But if you value the second option then somebody needs to step up with millions of dollars. And since it's primary funding comes from the National Science Foundation, which is not a priority in the current federal budget, who knows when that will happen.
Kapoor has negotiated an exclusive licence to use a particular material produced in a certain way... other materials with similar properties are available, and who knows, there might be reasons that Vanta Black is not the ideal coating for space vehicles.
Maybe microgravity vacuum is a suitable environment for depositing nanotubes on a substrate - i.e, develop a system for coating the satellites in orbit.
I think there can be over-heating issues if you paint the whole thing black.
Solar panels block the bulk of light from reaching the satellites, and I guess a pure black material would radiate back into space at not far off the same rate it receives heat.
Fasten a half-decent camera to the top of the satellite and use them as a huge distributed lens is my solution.
"a pure black material would radiate back into space at not far off the same rate it receives heat."
Only once it reaches equilibrium with the incident radiation, or to put it another way, once it reaches the temperature of the sun's surface.
Indeed: Black 3.0
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Can anyone provide a quick comparison between ground-based telescopes and space-based telescopes? I'd imagine that the advantage of ground based telescopes is ease of constructing very large structures. Is it impractical / uneconomic to use the ever cheaper access to orbit to launch a few big / many small telescopes for detecting asteroids?
Hubble cost 4 billion USD for a 2.4 metre mirror telescope, Gran Telescopio Canarias cost 130 million EUR for a 10.4 metre telescope. Considering a shuttle launch at the time cost 450 million USD, we can surmise that satellites are seriously pricey. For what they're looking to do, ground based is still the best option.
There are also thousands of ground based telescopes including those of amateurs, many important discoveries have been made or aided by them.
Still we can't let science and the potential it has to advance our knowledge while also tracking potentially extinction event objects get in the way of money, can we?
Having high speed internet everywhere in the world can be a game changer and one of the biggest equalizers we have seen. I’m in rural Canada and already have trouble getting the internet I need for work, can only imagine what difference it would make in less developed parts of the world. If it works and if it is somewhat affordable, of course.
Astronomy has survived worse, like our enormous light pollution. I’m sure we’re creative enough to fix this little setback as well.
Do you really think we're going to get worldwide internet from these? They're capable, but in order to get it, the companies have to operate in lots of places, manufacture the equipment for uplink at an affordable price, make it and service available to people who probably can't pay very much, and deal with regulations and censorship in some way. These are not easy things, and when you consider that these companies already have plenty of money, it seems unrealistic to expect them to invest all that much in providing service to places where the local population has any other option. You'll probably get service because Canada is wealthy, but large parts of the planet won't because the people in Chad can't even pay for a full roll-out of cellular.
If we add a healthy dose of skepticism to the worldwide equalizer potential, we have to ask ourselves if there's enough benefit in providing an extra coverage option to rural areas of the developed world to justify the interference to astronomy (and some other stuff as well, like other uses for LEO or potential difficulties for other uses of space). Might it be better to increase the availability of ground-based cable or cellular connection instead? This is not a question that has an exact answer, but if we temper our expectations of miracles of generosity from businesses that are certainly not going to provide it, we will be better able to discuss the real merits of the system.
Although it is an order of magnitude cheaper than during the Apollo launches, launching a kilo of mass into low earth orbit is still pegged at over $2700, which is not negligible.
There is another matter to consider, the volume available for launch. On the Falcon Heavy, Humanity's most capable launcher at this time, the available space to launch is 13.2 meters high and 5.2 meters in diameter. I'm sure boffins could fit a telescope in there - the Hubble space telescope is out there after all and it's smaller than that, although not by much.
So the problem is more along the line of we can launch another Hubble space telescope, but we can't launch anything bigger at this point in time.
The Falcon 9 doesn’t have that big a payload fairing which limits its ability to throw telescopes into space. This is one reason why NASA is going to use an Ariane 5 to fire the James Webb into orbit - if and when it is ever finished. If you want an all-American rocket for your telescope either the Delta IV Heavy or the Atlas 5 are the ones for putting mirrors into space.
Just wondering, and I'm sure this is a daft idea but I don't know why:
When they launch things into space, do they fill the voids with air, or vacuum or something lighter than air?
If it was filled with helium, it would reduce the weight and the amount of fuel required, wouldn't it?
(I assume they already do this or there's a very good reason why they don't)
Given the cost of lifting each kilo it seems like something I assumed they would already do ( presumably vacuum rather than helium ).
As far as I can tell, in the Falcon Heavy the payload capacity is 109m3. Lets say there's 50m3 of space around the payload, that gives 64kg of air.
$2720/kilo, comes to $174k just to lift the air.
That's not as much as I thought it would be, but I'm surprised that it's not worth saving.
What they are after is a wide field observation and the comparison of images between different timed shots. Some of the Earth-based versions use standard camera lenses. The mirrors therefore don’t need to be huge, and given a cheap launch it doesn’t need to be vastly more expensive than a ground based model given that they can use smaller mirrors in space.
> it doesn’t need to be vastly more expensive than a ground based model
Seriously? You say that using existing telescopes (zero investment) with standard low-cost cameras is only marginally cheaper than building brand new launch- and space-proof telescopes, and then buying yourself a big expensive launch to send them up there?
With the budget for a single space-based asteroid tracker telescope you could run hundreds of earth-based ones for years. The point you missed is that the earth-based telescopes already exist all around the globe, the cost of using them is minimal (staff pay, some minor maintenance).
The cost of optics is exponentially proportional to their diameter. A space based mirror can be much smaller for the same effective light gathering capacity (no atmosphere to dim and distort the image). As someone pointed out earlier in the thread, the Hubble telescope is only 2.4M, but is still able to look further into space than the largest, most powerful land based devices.
Again, to spot asteroids the main requirement is to cover a lot of space, not maximum magnification. The latest ground based wide-field scope that I’m aware of has a budget of about $28M. It’s not a big step from there to a space based device.
So, to summarise the above points:
Ground based: lots and lots of telescopes, can be made very big. Atmospheric interference not a deal breaker.
Space based: Just too expensive to put lots of telescopes up there, size is limited.
Okay, so let's look at twenty years in the future. Will there be enough telescopes in space to warn us of meteorites?
I'm assuming that for less urgent, purely scientific astronomy (the cosmos ain't going away any time soon) space or lunar based observations will eventually surpass any earth based telescopes, be this in fifty or years or a hundred.
Also, spotting an extinction-level rock hurtling towards us isn't too useful unless we can divert or destroy it. That will require getting hardware into space. The development costs of getting stuff into space have to funded somehow, be it by commercial satellites, military or state posturing.
Anyway, there's a professor at Oxford who set up a department for existential threats to humanity, and he places giant meteorites quite low down on the list - though they are devastating they are rare, and there are plenty of other ways we have of screweing ourselves over.
> less urgent, purely scientific astronomy [...] space or lunar based observations will eventually surpass any earth based telescopes, be this in fifty or years or a hundred
Yes, tell that to the new astronomers fresh out of college! "Sorry guys, you're born 50 years too early, we don't expect any serious research to be possible before some commercial entity decides there is money to be made on the moon and starts building bases we can use."
As for space-based optical telescopes, if they were that easy and painless to send up there, why do we only have the (fairly old now) Hubble up there? Why haven't we sent a dozen or more of those up, if they are so cheap and simple to build?
is such a dick!
no one asked for or wanted these. Space X didn't ask any country whether they were happy to screw up the night sky for every country in the world. Yet he carried on doing it.
The same guy who told everyone his wife was dead when they broke up & who called a guy a paedo because he told him that his submarine wouldn't work in the tight confines of a cave.
I've not managed to find a balanced opinion on this issue (not knocking El Reg here, they are reporting on other peoples statements and are not themselves "space experts"). It seems to divide into "This is the end of all astronomy as we know it and don't come running to us when an asteroid hits us" and "seriously, there is nothing at all to worry about here". Presumably the truth is somewhere in the middle.
I will admit to finding the "oh, it's just for cat pictures" a bit tiresome though. Starlink at least have said that their pricing will probably be based on ability to pay. i.e. cruise ships, airlines, etc. full of (comparatively) rich people will pay full wack to get their cat pictures but remote villages in less developed areas of the world will not. They may even get the equipment/bandwidth for free and can then get access to health information, education, etc., etc. So there is opportunity for genuine global social good to occur here and that does need to be considered along with the other positive/negative aspects of these large shiny constellations...
> opportunity for genuine global social good
You seriously believe this??? OMG.
That's unicorn-rainbow-level BS, simple marketing speak to counter the bad press they're getting for polluting the skies and to avoid somebody doing something against it.
It's the local version of "Won't somebody think of the children!". Indeed, won't somebody think of the poor innocent children of those "remote villages in less developed areas" who will all die horrible deaths because they can't access Facebook?
Or do you think what passes as "health information" on Internet (written in a language they don't understand) will help them in any way? "Buy cheap canadian meds" isn't what they need, they need real doctors who speak their language and understand their lives. Same for education, you won't learn to read and write on YouTube. (Assuming you can afford a computer and have electricity.)
Unless of course those "remote villages in less developed areas" are supposed to be in the USA, in which case the sensible thing would be to pull some fiber/cables. I'm pretty sure it wouldn't cost as much as sending up and managing thousands of satellites. But of course there is less profit to be made too...
Sure, the proof is in the pudding, as they say. But in few years it will be clear whether they intend to deliver on it and we can make our judgement then.
In terms of the information access (health, education), no I'm not interested in everyone on the surface of the earth having access to facebook/google/whatever. But this technology could allow a massive expansion to _existing_ successful education and health programmes run by charities and local governments across the poorer areas of the world.
Imagine: a one-off trip to a remote village could deliver a package of a small generator, a couple of solar panels, a few recycled laptops and smart phones and a satellite linked wifi hotspot. Now there is easy communication to the nearest town or city and, for example, health information by video link, lessons and remote learning for school age children, weather and crop advice to farmers. These schemes _already_ exist but are limited by the technology. i.e. need long range radio links or to be within an easy extension of a existing mobile infrastructure. With Starlink (or similar) there is no longer any need for ground infrastructure of any kind and the only geographic limitation is can the kit get transported there and can a basic low power electricity supply be maintained.
Maybe things have changed since I last read about these schemes and maybe most people are now in feasible range of existing, reliable comms infrastructure of some kind - but I doubt it.
It's not for me to say that these benefits outweigh the downsides of these large satellite constellations, but, yes, I do believe that there are potentially amazing benefits to be had across the globe. Not for me, because I've got my fibre broadband thanks very much, but for others.
I think you're getting overoptimistic. There are certainly good uses for an internet connection everywhere. No disagreement. However, I remain entirely unconvinced that these satellite plans will ever put internet there. The reasons for this are many, but here are a few of the big ones:
There are lots of small places that don't have internet. You could try to assemble connections for all of them, but that will mean having a lot of people whose main job is finding places, talking to the people there, assembling the devices to send over, getting them in, setting them up, etc. Charities might do some of this, but I don't expect the companies to find charities and offer them several thousand satellite uplinks.
Here's another problem: have you ever managed to get an internet connection online as easily as the ISPs claim? I haven't. I know how to plug in my wires, but I've often had to call up their support line and get them to realize that they never turned the line on, they haven't enabled my account yet, they forgot but a technician needs to come by and do [they're certainly not telling me what], or they had me down as having a billing problem because they took my last payment and applied it to someone else's account (this has happened to me). I recently helped a friend who set up a new connection which didn't work and the ISP informed us that they provided the wrong equipment and we had to go to a retail outlet to exchange it for the right equipment before anything would turn on. What I fear is that the same thing is going to happen to these. If the companies are going to provide free service, they will still have a billing system and something to cut people off. If the connection fails in one of the various disconnected places for an account broken reason, maybe because the village doesn't pay their nonexistent bill or even the connection went down for a long while while a storm affected the equipment, how are the people there who don't have an alternate communication system going to get someone on the American or European call center to understand the problem. In fact, how are they going to call the call center or identify themselves? What happens if the satellite dish is broken? How do they notify someone and get a repaired unit? Will they get a repaired unit?
One more consideration is how much a for-profit company cares about any of this. It doesn't make them any money, and it has various administrative problems. In order to manage something like this, they need to have business in countries they probably get nothing from, verify that some location qualifies for reduced-price or free equipment and service, handle tech support and repair, manage the risk of equipment theft, and many other things. Each one of those things takes time and money, and the company gets nothing from it. How long will it be before someone from finance lays out these figures and suggests a few other options. There's a cheap way to pretend to care without doing this--you manage the free connections for developing regions project yourself, find a few photogenic schools that don't have connections, provide service for like four of them, and post those stories on your main page. What will stop the companies from doing that?
The projects you suggest are important, and people are currently doing some things in that area. There are projects to collect educational materials and get tech to students. Projects to provide extra communication equipment to far-flung areas. Projects to increase the availability of medical advice and basic medical knowledge when hospitals are too far away. These projects have a real, generous, verifiable purpose. I am not convinced that these satellite internet plans care about any of this rather than the profits they're expecting.
What do you think happens when the tech in a remote village stops working, or gets a bug or some other fault? Unless you have someone skilled nearby to maintain the hardware and fix software problems, this idea is of limited use. Not to mention conditions in the tropics are very challenging for lots of tech (humidity, dust, ants etc.), including the fact that monsoon showers block wifi signals. So for 2-3 months of the year, coverage will be spotty anyway. For many remote areas, anything short of military spec tech won't cope with the conditions.
I'm sure there are places that will be helped, but I also doubt moneymaking is the secondary concern here.
> the poorer areas of the world
Let's for starters define what you mean by "the poorer areas of the world". There is a huge difference if we're speaking about some backwater area of the USA, or some drought and war struck area in Africa (for instance).
Internet would benefit to the former, but definitely not to the latter, they simply don't have the first-world problems we have, and in such areas any computer would have a snowflake-in-hell life expectancy anyway. Most likely they would be stolen by the local warlord the very next day and sold for weapons and ammunition, at best they will die some weeks later when the sand and dirt clogs the vents, or simply when (not if) the generator breaks down, is stolen or sold for money.
What those people over there really need is peace (absence of war), clean water and enough food. Internet satellites don't deliver any of those, which is why I'm pretty sure the "Think of the children" excuse is just an outright lie.
How bad it gets will depend on how many satellites actually end up there and in what orbit. There is the potential for this to be seriously disruptive and increase the time and effort (and cost) of earth-based astronomy. Some of the numbers in play suggest any half decent frame will have one of these birds in it somewhere.
Of course, the trouble with predictions is by the time we can prove they are correct, it will be too late.
Not sure if you have seen this animation on
After about 5 seconds or so it settles down to real time animation
The marked Location is not too far from me in north west London and it shows a steady stream almost overhead.
Also on the same site is a live sky view. Enter in your lat/long and it shows all the ( visible) space junk passing through your sphere of vision. looking at mine a few minutes ago showed 5 of musk's demons travelling west to east.
They're damned difficult to see though, especially the later ones. Occasionally you'll get a flash as the sun reflects off their solar panels but it's very brief. I've seen more flashes than I have demons.
"They're damned difficult to see though, especially the later ones."
Unseen objects occulting stars is a source of noise. Imagine a photo of a galaxy with darkened streaks because satellites kept passing through the shot.
The best case is you take extra frames and bin those which are calculated to contain a satellite before integrating. That's still fewer observations in the time available.
I'm just amazed by the folk here, using the internet, effectively saying that other groups of people don't deserve the internet because they'll only use it for cat pics and pr0n - just because they live in the rural USA or a remote African village.
That's utterly fallacious. It's even a textbook direct "ad hominem" attack!
Nobody said "they don't deserve" anything, we just say the price is too high for what it is.
To put it in simple terms: Internet yes, but not by sacrificing astronomy. Not if there is some other solution (Hint: There is.).
It's a tougher question than it looks. Good Internet access for poor countries and rural areas is all kinds of useful, not just for slinging porn. Honestly, while I would not sacrifice amateur astronomers' hobbies for the sake of cat videos, I would for the sake of, just off the top of my head, improving access to education or easier trade for farmers in third world countries. Besides, in a world of hundreds of thousands of satellites, an amateur astronomer might be able to rent time on a space-based small telescope for cheap, and that would be pretty cool.
But I'm more concerned about professional astronomy, and I don't see a way to easily have our cake and eating it too there. Ultimately, the ideal situation would be one where serious astronomy is mostly done from orbit. Observing stuff from space would be better even without the satellites getting in the way. Think what we could see with an orbital telescope that's as big as some of our ground-based ones!
The problem is that building such a thing is economically unfeasible, unless we either get launch costs way down, or we get way better at building stuff in space. Neither of those things is going to happen unless space gets profitable. So, yeah, tough question.
These satellites are not really for poor countries. They are getting or have mobile and fibre. The fact that many are mortgaging their resources and other infrastructure to China to get it is a separate problem.
The fact is that almost no-one actually needs these. The real use is a very niche market and the quantity isn't needed for cruise ships (which are stupid) or air travel (of which there is too much). Even with 10,000 the capacity is tiny for any given area because they are in LEO.
Deploying fibre in rural areas is vastly expensive, and mobile data is still expensive while proving much less bandwidth. Even in the first world (rural USA for example) then sparsely populated areas have little or no (ground based) connectivity. There are large parts of the world where this kind of connectivity would be a godsend.
My wireless BB is a lot cheaper than Musks offering. I somehow doubt rural Africa is going to turn into an economic powerhouse because it can watch netfils and disney simultaneously when all it really need is access to local markets which wont be able to afford Musk either.
More expensive than mobile BB? Only if you think in terms of 1 or a couple of users for a base station. One base station coupled to a wifi Hotspot could provide for a whole village. Also there are large lumps of the US where even 3G isn’t available, how much have the US companies spent on rolling out their service so far?
<how much have the US companies spent on rolling out their service so far?>
Very little which is why you have large parts of the US without coverage but some very well looked after Representatives who look the other way when the big telco's forget to spend the millions that they have been given to expand the network. Coupled with lobbyist money to ensure that laws are written using telco ink to remove competition and an FCC that removed its own oversight at the telco behest and you have some very messed up communications in the US!!
It is not a reason to fill the night sky with satellites though - if the US fixed it's telecoms issues and forced the industry to do what they promised, I wonder if Musk would be as keen to throw his starlink up there - probably, it's as much a vanity project as a commercial one...
There are other ways to get service to rural areas. Fiber is not quite as expensive as you think. It gets divided per user, which means it doesn't happen, but when compared to the price of launching lots of satellites, not quite as much. There's also geosynchronous satellite, which is a little annoying from a latency perspective but it works without polluting orbits and covers a large area. You can cover lots of places by doing that. If someone really wanted to get service over the massive areas that don't currently have it, they could do so more easily with a small number of geosynchronous satellites or investments in local fiber and cellular providers. The benefit to Starlink and those like it is smaller and mostly focused on already-developed countries. For one thing, it allows those companies to get licenses to use orbits and radio frequencies that are worth quite a lot. For some areas, they will have captive markets because land-based ISPs have been ignoring their requirement to serve rural customers. It will provide better service to ships or aircraft. It allows companies to justify investment in rockets that nobody else is using. They get an early-mover advantage on LEO, and can rent out that expertise to other companies. And it's a way to waste money if you have a lot.
We now have to decide if those benefits are enough to justify the harm to others. We should be considering the real benefits, not the possible benefits that could happen but probably won't. If we allow companies to fill the argument with could-happens, we're going to lose no matter what side we're on.
Which is the reason that ISPs often get government subsidies for running services to rural areas. Also why houses that are further away often use copper instead of fiber. Copper lines are worse, but if properly maintained, they're fine. The original point, that it is quite possible to connect these places without requiring satellite, remains. Just because the ISP near that house didn't choose to doesn't necessarily mean there's a problem requiring LEO satellite to fix. The original copper line going there (I'm pretty sure there is one) could carry data. The ISP could be required by regulation to maintain that. The regulator could enforce that by issuing fines to ISPs which fail to do so. Problem solved.
The argument being made here is basically that this satellite constellation provides service where it wasn't feasible to provide it, or at a much cheaper price than it could. This doesn't mean that it is cheaper than the most expensive alternative run only to one building, most things are. The argument that must be proven is that it is cheaper or better than an alternative which also provides reliable service of sufficient quality when calculating the prices to run that service to all who will be using it. All of us have to sacrifice our own amateur astronomy desires and benefits we get from ground-based astronomical equipment, as well as extra difficulties in space and a more restrictive monopoly on radio spectrum. If it only helps in a small set of places, it may not be worth it. If you raise the bar for alternatives to make it seem better, you're just muddying the waters without actually improving things.
If you're developing a country, it costs little to lay fibre down *before* you pave the the first roads. Even less if you do it at the same time.
I'm not coming down on the side of fibre vs satellite, though. Too many other complex factors. Sociopolitical, for example - how many tyrannical governments like shutting down internet access, how many twats like to set fire to cell phone towers or microwave relays? How much of our essential infrastructure such as food distribution and emergency coordination relies on the internet, and how resilient is ground based infrastructure to storms, fires, trawlers, civil unrest etc?
"I'm not coming down on the side of fibre vs satellite, though. Too many other complex factors."
Here are some considerations that will apply, making most of those factors unimportant or nonexistent.
"Sociopolitical, for example - how many tyrannical governments like shutting down internet access,"
These systems have already agreed to comply with governmental censorship. They have to. If someone sent up a satellite to do two-way comms in an area where censorship was going on and didn't respect the government's regulations, the government would go around with radio vans and find people who are transmitting to those satellites. The dishes would be smashed and the users imprisoned. If that country had the ability to further punish the satellite operator, they would. The point being that if a government wants to cut off the internet or mess with it in a different way, they're still going to do so even with this system.
"how many twats like to set fire to cell phone towers or microwave relays?"
I've seen people attacking towers, but relays don't seem to be as targeted or as vulnerable (they're not as densely packed so the operators can afford to secure them). The problem is that, after the signal goes from the user to the satellite, it still has to come down somewhere and go to the other services run along the ground. Satellite manages to make extra paths for the last hop from ISP to user. It doesn't liberate us from the rest of the ground-based network.
"How much of our essential infrastructure such as food distribution and emergency coordination relies on the internet,"
A lot. You can try to make a satellite web, but if the internet goes down around the downlink places, it's not going to do you any good. If you want to make those things not be so reliant on the internet, you have to use something different. Point-to-point radio link, satellites that don't downlink and connect two devices on the same network (not what these constellations do by default). Those are good ideas, but this doesn't accomplish them.
"and how resilient is ground based infrastructure to storms, fires, trawlers, civil unrest"
If we're going to worry about those things, we have to worry about several other things. First, we have another ground-based thing that runs to all these places: electrical power. Can you run the satellite receiver from a battery easily available to users? I'm guessing it takes something larger like a UPS, which most houses don't have. Second, how resilient are satellite dishes to those things? A storm can smash them or knock them out of alignment. Fires can release smoke which occludes or corrodes them if it doesn't just burn the building down. Civil unrest can cause damage if people want to use hammers. Third, you could ask similar questions about the satellites, as they may have resilience problems to radiation, collision, or overwhelming traffic. Finally, you still have to take into account that the satellites are relying rather heavily on ground-based downlink to provide all their services.
This is story from quite a few years ago. A colleague in the Republic of Ireland relied on satellite internet, because he lives out in the sticks, where high speed wired connection would not be economic to implement. There must be many places in the world where the same economics apply.
I think the cost of space telescopes is due to come down considerably, due to reduced launching cost, which Elon Musk is helping.
The economic and technical case for LEO internet is weak. It's better to increase rollout of fibre, coax (fibre to street) and more mobile masts.
Perhaps in 10 to 20 years these will be gone.
The capacity per 10 km is a tiny fraction of mobile which is a tiny fraction of fibre or fibre to the kerb solutions. They also have a poor operational life and the launches are environmentally poor.
Hmmm... Take half a dozen Starlink frames and bolt them together, keep the command and control bits, propulsion system and solar array from one of them, and you've got a nice bus for a 1m telescope that could be launched along with a batch of actual Starlinks. Feels like a nice student project to sort out a design that could be easy to manufacture and put several into orbit.
So the scenario is theres an asteroid thats going to hit the earth and destroy the whole thing only we cant see it because of all the cat GIF distribution satelites......
Who cares? If said asteroid was gonna hit theres nothing we can do to prevent it so why not spend our last few minutes in blissfull ignorance looking at cat gifs?
We had a relatively near miss at the start of June this year from asteroid 2020 LD. A mere 100-150m in diameter, and it came within 200,000 miles of the earth (that's closer than the moon). It was only big enough to wipe out a medium sized town, say something like Bath, but if we saw it coming, then we could at least evacuate those in the danger area. As it happens it wasn't spotted until two days after its closest approach, and that was nothing to do with Musk's satellites, but down to it making a sneaky attack from the direction of the sun, but the point is, there are things that we can do, if the asteroid isn't too big.
probably, yes. if they had sufficient good data on the asteroids path. Generally they are lumps of rock coming straight in at very high relative speeds. They take so little time to pass through the atmosphere (don't believe Hollywood!) that they don't get diverted by it much. The biggest uncertainly (for certain size ranges, at least) is whether it will make it to the ground in one lump or whether it might explode into fragments on the way in. For example, the Chelyabinsk event from entry to fragmentation was about 15s (after-effects obviously lasted longer).
Satellites are a bit harder as they are very small and it is atmospheric drag that brings them down. For that you need to track them and model the effect of a non-streamlined irregular object interacting with the outer wisps of the atmosphere (which grows and shrinks), etc. So what starts as a very gradual slow down and de-orbit can suddenly suddenly change into a much more rapid descent if it "digs in" or the outer atmosphere is a bit thicker than expected that week, etc. For the last large object that I can recall (which I think was the Chinese prototype space station) the impact estimates were updated regularly and became increasingly accurate as it orbited closer in and the atmospheric effects became more consistent.
This isn't a case of seeing an asteroid a few days before it hits us. It is case of seeing an asteroid that comes near us, and we calculate its orbit and find out it will hit us in decades. We certainly could do something about that, especially since the asteroids we'd discover in this way are relatively small (we don't need to look so hard to see one of the six mile wide dinosaur killers)
Almost all such discoveries are made using longer exposures (but still short enough that faraway objects like stars and planets are still points of light) and looking for light tracks.
If a track is observed they have to go through a process to rule out known objects orbiting Earth that reflect light, such as the space station or various NEO satellites (some of which, like spy satellites, will occasionally alter their orbit) That's already difficult with the number of objects in orbit, when the number of such satellites is increased hundreds of times larger that process will become untenable. Every image taken will contain light tracks, and almost all of them will be false alarms.
If all we were concerned about was potentially dangerous objects approaching Earth, why not add basic cameras to each satellite launched, designed to point outwards. Stream the image along with the rest of the data and stitch the data together. Run them at a lower resolution the majority of the time if you're concerned about the bandwidth used (and the sheer volume of data accumulated) and just switch to high-resolution when there's something that warrants further investigation.
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