4 ms·

Lasers between them in orbit is what I've heard, nothing about ground stations, AFAIK.

_bxg1 7y ago
I could've sworn somebody was planning to use lasers to communicate from the satellite to a ground station, claiming it would improve latency. Maybe I misread.
- jsjohnst 7y ago
  Lasers alone won’t improve latency, but they would certainly impact reliability. Radio waves already travel at essentially the speed of light.
- Rebelgecko 7y ago
  It's been done in the past. I think the main benefits are preserving EM spectrum and some theoretical improvement in bits per watt
m12k 7y ago
Yeah, probably not much point in making an internet connection that only works without cloud cover.
- yellowapple 7y ago
  I'd imagine a laser at typical radio wavelengths would be just as susceptible to cloud-cover-induced interference as a non-laser at typical radio wavelengths, no? Not that even lasers would be necessary to mitigate jamming; ordinary beam-forming / directional antennas should be enough (barring some really sophisticated jamming technology of which I'm not aware, or the Iraqi government putting up and maintaining permanent chaff clouds or something similarly outlandish). Jammers (to my knowledge) operate by actively producing an inverted copy of the signals it actually sees. That is: it'd be reliant on non-directional signals. Any directionality / beam-forming would make jamming a lot harder, since it makes it a lot harder for the jammers to actually see the signal in the first place (let alone produce an inverted-waveform copy of it). Jamming also tends to get in the way of other radio communications, so even if it was actually effective against satellite communications, it'd be a last resort and would likely cause all sorts of other issues.
  - TeMPOraL 7y ago
    > Jammers (to my knowledge) operate by actively producing an inverted copy of the signals it actually sees. No. Usually, all you need is to do is to send a signal - any signal - on a frequency you want to jam with enough power to overwhelm the target signal. A directional antenna won't get a milliwatt satellite signal if it starts picking up half a kilowatt of random noise, even if that noise is coming from the side. It's essentially a matter of how much power your jammer radiates and how high you can put it. Whether or not jamming interferes with other radio communication depends on how much of the spectrum your jamming signal covers.
    - yellowapple 7y ago
      Seems like it'd be pretty straightforward to block signals coming from the side (e.g. by putting some metal or something else similarly RF-blocking between the antenna and the jammer), no? Kinda like how wearing a hat helps keep the sun out of your eyes. Actively jamming the jammer (i.e. inverting the signal received from the jammer side and rebroadcasting on the the antenna side) would help, too, though this probably makes it easier to detect. And yeah, the higher the jammer, the harder it is to block it without blocking the signal you're trying to actually see (but it's still possible; if it wasn't, then modern astronomers would have a much harder time picking out interesting things amidst the menagerie of cosmic background radiation bouncing about). There are plenty of other strategies, too (like not sticking to a single frequency, or picking frequencies that are likely to be too valuable to block with such a blunt-force method).
      - TeMPOraL 7y ago
        > Seems like it'd be pretty straightforward to block signals coming from the side (e.g. by putting some metal or something else similarly RF-blocking between the antenna and the jammer), no? Depends on the wavelength and your surroundings. Imagine yourself wearing a cap that's little too small and half-transparent on the edges, walking on fresh snow, surrounded by snow mounds, trying to spot something on one of the hilltops nearby. So the cap mostly protects you from direct jamming signal, but reflections and bleed are still painful. Now we're talking here about satellites, in particular LEO satellites, so you need a mass market (or at least commercial-grade) tracking antenna, which will have to look all across the sky and not just point straight up. In urban environments, there's a great chance there will be scores of decent reflectors (buildings) all around you for the jamming signal to bounce off, and as for bands, the ones used by Starlink are ones that are unlikely to be used much for anything else in places like Iraq - so they may as well just jam the whole band. And since Starlink is a commercial service, you won't be able to switch to something the government depends on (not to mention procure new antennas and adjust software on the transceivers).

I could've sworn somebody was planning to use lasers to communicate from the satellite to a ground station, claiming it would improve latency. Maybe I misread.

jsjohnst 7y ago
Lasers alone won’t improve latency, but they would certainly impact reliability. Radio waves already travel at essentially the speed of light.
Rebelgecko 7y ago
It's been done in the past. I think the main benefits are preserving EM spectrum and some theoretical improvement in bits per watt

m12k 7y ago

Yeah, probably not much point in making an internet connection that only works without cloud cover.

yellowapple 7y ago
I'd imagine a laser at typical radio wavelengths would be just as susceptible to cloud-cover-induced interference as a non-laser at typical radio wavelengths, no? Not that even lasers would be necessary to mitigate jamming; ordinary beam-forming / directional antennas should be enough (barring some really sophisticated jamming technology of which I'm not aware, or the Iraqi government putting up and maintaining permanent chaff clouds or something similarly outlandish). Jammers (to my knowledge) operate by actively producing an inverted copy of the signals it actually sees. That is: it'd be reliant on non-directional signals. Any directionality / beam-forming would make jamming a lot harder, since it makes it a lot harder for the jammers to actually see the signal in the first place (let alone produce an inverted-waveform copy of it). Jamming also tends to get in the way of other radio communications, so even if it was actually effective against satellite communications, it'd be a last resort and would likely cause all sorts of other issues.
- TeMPOraL 7y ago
  > Jammers (to my knowledge) operate by actively producing an inverted copy of the signals it actually sees. No. Usually, all you need is to do is to send a signal - any signal - on a frequency you want to jam with enough power to overwhelm the target signal. A directional antenna won't get a milliwatt satellite signal if it starts picking up half a kilowatt of random noise, even if that noise is coming from the side. It's essentially a matter of how much power your jammer radiates and how high you can put it. Whether or not jamming interferes with other radio communication depends on how much of the spectrum your jamming signal covers.
  - yellowapple 7y ago
    Seems like it'd be pretty straightforward to block signals coming from the side (e.g. by putting some metal or something else similarly RF-blocking between the antenna and the jammer), no? Kinda like how wearing a hat helps keep the sun out of your eyes. Actively jamming the jammer (i.e. inverting the signal received from the jammer side and rebroadcasting on the the antenna side) would help, too, though this probably makes it easier to detect. And yeah, the higher the jammer, the harder it is to block it without blocking the signal you're trying to actually see (but it's still possible; if it wasn't, then modern astronomers would have a much harder time picking out interesting things amidst the menagerie of cosmic background radiation bouncing about). There are plenty of other strategies, too (like not sticking to a single frequency, or picking frequencies that are likely to be too valuable to block with such a blunt-force method).
    - TeMPOraL 7y ago
      > Seems like it'd be pretty straightforward to block signals coming from the side (e.g. by putting some metal or something else similarly RF-blocking between the antenna and the jammer), no? Depends on the wavelength and your surroundings. Imagine yourself wearing a cap that's little too small and half-transparent on the edges, walking on fresh snow, surrounded by snow mounds, trying to spot something on one of the hilltops nearby. So the cap mostly protects you from direct jamming signal, but reflections and bleed are still painful. Now we're talking here about satellites, in particular LEO satellites, so you need a mass market (or at least commercial-grade) tracking antenna, which will have to look all across the sky and not just point straight up. In urban environments, there's a great chance there will be scores of decent reflectors (buildings) all around you for the jamming signal to bounce off, and as for bands, the ones used by Starlink are ones that are unlikely to be used much for anything else in places like Iraq - so they may as well just jam the whole band. And since Starlink is a commercial service, you won't be able to switch to something the government depends on (not to mention procure new antennas and adjust software on the transceivers).