Free-space optical links for space communication networks
arxiv.org
arxiv.org
I'm calling it tight-beam and you can't stop me
When I worked in the television industry, it was how some of the TV stations in New York world get their skyline video back from their towercams in New Jersey. This was late 1990's.
It was my understanding at the time that it didn't work well in rain and fog, but that was O.K., because there was nothing to see then, anyway.
Add on boats & airplanes - and now we really are in the 21st century (not trying to sound glib, I have wanted this for a long time).
:)
Where do you live? In most of Europe and SE Asia you can get gigabit broadband.
I think SpaceX is a cool company and I could see myself work there, but StarLink is, IMHO, a shitty project that ruins the night sky and space for everyone. https://en.wikipedia.org/wiki/Starlink#Criticism
What if we could churn out orbital science platforms as fast as SpaceX churns out Starship SNs and StarLink satellites?
This is light pollution.
Increasing global networking, and doing so in a ground-infrastructure-agnostic way, has the potential of connecting billions of people to the global internet in a cost-effective way.
Sometimes, progress outweighs the cost.
And parent comment presented a nice alternative approach for the specific astronomy case.
Try searching for ISS :wink::wink:
No, you've misunderstood (in numerous ways, but this is a specific one you've cited). That photo you linked is of a satellite "train", which is a temporary state of satellites after deployment as they take themselves the rest of the way to final deployment orbits. At that point they'll be both spread out and the albedo will be vastly lowered because SpaceX has already made design alterations to the sats so that in their operational alignment towards Earth they are far less reflective. They're not going to interfere with the sky from the naked eye, nor even for general photography, even from low light pollution rural areas vs typical urban ones.
It doesn't help that you're almost a parody of "entitled, dismissive urbanite". Even in the developed world, tens to hundreds of millions of people have crappy DSL at best. Outside of the developed world that rises to billions. Marine and aircraft stand to make enormous gains as well. The demand for Starlink is clear and well founded, and you do your argument zero favors by trying to hand wave it away (unless you just mean to rant to no constructive end).
I have provided a Criticism section of a Wikipedia article that points out light pollution criticism from many authoritative sources, including photographic evidence. You dismiss this photographic evidence, but why should I listen to you when I can listen to the IAU, for example? Or Nature? Or the astronomical community?
Quote International Astronomical Union: "The scientific concerns are twofold. Firstly, the surfaces of these satellites are often made of highly reflective metal, and reflections from the Sun in the hours after sunset and before sunrise make them appear as slow-moving dots in the night sky."
Here's an entire article in Nature Astronomy about the issue https://www.nature.com/articles/s41550-020-01238-3
Here's a quote from a Senior Advisor to the European Space Agency https://twitter.com/markmccaughrean/status/11323943469454213...
Here's an entire discussion at the American Astronomical Society about the issue https://aas.org/posts/advocacy/2020/12/impacts-large-satelli...
Here's an article about how the problem will get workse https://www.scientificamerican.com/article/spacexs-dark-sate...
But sure, you call me an "entitled and dismissive urbanite".
>Aggressive space activities without adequate safeguards could significantly shorten the time between collisions and produce an intolerable hazard to future spacecraft. Some of the most environmentally dangerous activities in space include large constellations such as those initially proposed by the Strategic Defense Initiative in the mid-1980s, large structures such as those considered in the late-1970s for building solar power stations in Earth orbit, and anti-satellite warfare using systems tested by the USSR, the US, and China over the past 30 years. Such aggressive activities could set up a situation where a single satellite failure could lead to cascading failures of many satellites in a period much shorter than years.
Incorrectly, fortunately. First, remember space is big. At hundreds of km up, even tens of thousands of satellites are by definition spread across a greater "surface" area than the entirety of the Earth. There will be fewer of them then there are aircraft flying through the skies.
Second, you might find it reassuring to look up orbital drag. The atmosphere doesn't simply stop at some set point, but rather gradually thins to irrelevance (or arguably to the bow shock of the solar wind). But anything below 600-700km or so requires regular reboosts or else it will experience decay (eventually exponential) and burn up/crash (depending on construction and design). SpaceX is leveraging its launch capabilities to have lower satellites which don't last as long, but offer superior performance, eliminates many of the space trash concerns, and doesn't lock them into design decisions nearly as much.
I mean, is this really such a surprise? SpaceX of ALL players clearly has enormous vested interest in making sure space access remains straight forward. Like, that's their entire foundation of business. If LEO really was closed off, no more SpaceX.
>including photographic evidence
Yes, which I specifically addressed, and which you have in turn completely ignored. I've followed this as well, and through much more authoritative sources, but in this case your own example was the direct cite. You said "the photo from Germany" which must refer to the one there captioned "Starlink in Tübingen, Germany". But that photo clearly depicts a deployment train, not Starlink satellites fully deployed. Because they don't line up in a train like that in final operational status. That trains might be visible in photographs for a few weeks out of a 5 year lifetime is a very different argument. The caption also does not state what generation they were.
>the surfaces of these satellites are often made of highly reflective metal
Which is generic hogwash. We're not talking about "surfaces often made of" we're talking about Starlink, specifically. Which, as again your own link states:
>"More recent satellites have visors to block sunlight from reflecting from parts of the satellite to reduce its albedo further."
Operational satellites won't be in a train, will be oriented in ways that reduce reflections, and they're actively working on measures to further mitigate albedo. And a core aspect of Starlink is that they have a rapid lifecycle. The impact will probably not be zero, but that must be weighed against the benefits. And the benefits are huge.
>But sure, you call me an "entitled and dismissive urbanite".
I will indeed, because that is how you are acting. Your "Where do you live? In most of Europe and SE Asia you can get gigabit broadband" is flat out INSULTING. I (nor SpaceX for that matter) do not in fact live in Europe or SE Asia (and of course you're implying those outside "most of" are unimportant even there but whatever). I live in America near the Canadian border. I've been fortunate to have 5/1 ADSL from 2000 up until a few years ago with an ISP who were at least local and nice and only charged $45/month for it. Just 40 miles away I know people paying $270/month for 10 megabit service. Others have dial-up or horrible GEO sat internet options or nothing. Many friends in Canada are in the same boat, and that's in the developed part! Take a look at the official Canadian Government National Broadband Internet Service Availability Map:
https://www.ic.gc.ca/app/sitt/bbmap/hm.html?lang=eng
Take some time to go through a few of the layers if you like, but maybe for an initial gut check go to "Aggregated Presentation" and take a look just at "5/1" coverage. And then look at all the empty spots. You can live within 20 miles of the national capital and not even be able to be certain of 5/1 internet. America is in a similar boat, though without as reliable data because the FCC coverage maps are ludicrously generous to industry right now (if even a single household in an entire census block has broadband, the census block is "covered" yet even then massive numbers aren't).
Frankly, even if it really did come down to your subjective feelings about "the night sky" versus decent broadband options for the entire planet? Well you lose. I personally don't think it will be that bad long term, because nobody wants it to be zero sum. There will be continued improvements in lowering albedo, and Starship's massive reduction in space access costs will allow vast new space-based telescope efforts. Heck, we might even ultimately actually get fiber and/or decent WISPs all over the planet, and thus be able to reduce constellations to just what is needed for marine/air.
But the biggest "light pollution" sources for most of the public are ground lights, and astronomers are going to have to accept some compromises for a while because universal broadband is really genuinely important.
> you do your argument zero favors by trying to hand wave it away (unless you just mean to rant to no constructive end)
Personal attacks and name-calling are not ok here, regardless of how right you are or feel you are. Please omit such swipes when posting to HN.
Nevertheless I accept judgement of you and community here and will try to more carefully consider replies down the road.
On page 26, it seems the primary application is being able to get more data down to Earth for remote sensing applications.
The most important application of lasercom from LEO is direct-to-ground downlinks since the main point is being able to download to Earth the increasing amount of data that remote-sensing missions require
There's interesting considerations in space laser communications that you don't see in fiber such as "point-ahead" optics to account for the fact that the speed of light is finite and the target is moving. This can be thought of as the optical equivalent of peeing into a moving bucket.
It's a fascinating review article.