SpaceX sends laser-linked Starlinks to the polar orbit

Re:SpaceX sends laser-linked Starlinks to the polar orbit by ornornor on Monday January 25, 2021 @03:41PM (#25908511)

Can’t anyone (well, anyone with state kind of money) observe the laser and at least dump it with perfect accuracy to keep for later decryption? I’d think tapping n undersea cable is more work than observing light going from sat to sat? I’m just spitballing here, I have no idea what’s possible or not but I’d be curious to know.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by JumpCrisscross on Monday January 25, 2021 @03:48PM (#25908624)

> Can’t anyone (well, anyone with state kind of money) observe the laser

LEO is far from a true vacuum. But it's sparse enough that you have limited beam scattering. Getting a read on a sat-to-sat laser emission from the ground is nontrivial.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by TeMPOraL on Monday January 25, 2021 @05:09PM (#25909618)

What about scatter from the satellite itself? The laser can't be perfectly absorbed on the receiving end. I haven't done the calculations, but I fully expect the spot size is much larger than the receiver.

That said, I imagine that for any serious bandwidth, you won't get enough SNR to decode anything from the ground.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by lutorm on Tuesday January 26, 2021 @12:37PM (#25918769)

Remember that the only reason a laser works for this kind of link is that it is very highly collimated. The light scattering from the receiving satellite is diffuse so the intensity will go down very quickly with distance. It might be observable with a suitably large telescope, but I doubt it would be practical.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by ska on Monday January 25, 2021 @06:34PM (#25910454)

So you have a reflection off random bits of equipment followed by a trip through most of earths atmosphere? That doesn't sound easy at all - and they could choose wavelengths that won't make the trip well if at all.

I guess if you got an observation platform up closer that would help.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by bsdetector on Tuesday January 26, 2021 @04:24AM (#25913924)

More like farther away. Put a spy satellite in a high orbit like traditional satellite internet and it'll be able to see half of Starlink simultaneously with essentially no distortion.

If they were strongly encrypted there may be no reason for a nation state to observe the intersatellite links, but I wouldn't expect this at least for the near future since Elon's focus will probably be to cut corners to get the absolute best performance possible.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by bob33212 on Monday January 25, 2021 @04:37PM (#25909253)

If it is encrypted and you drop just a couple bits due to noise you can't read it.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by jsrcout on Monday January 25, 2021 @06:29PM (#25910410)

There are multiple layers of encoding to mitigate this. CCSDS [0] is very widely used for satellite communications, and a Google image search for CCSDS protocols [1] will give you a quick view of the protocol stack (which can vary a lot as different CCSDS protocols are used in different applications).

[0] https://en.wikipedia.org/wiki/Consultative_Committee_for_Spa...

[1] https://www.google.com/search?q=ccsds+protocols&source=lnms&...

Edited to add: I'm not making any claims on what protocols Starlink uses specifically. Just describing the general approach.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by jandrese on Monday January 25, 2021 @03:47PM (#25908597)

I think it would require someone to fly a spy sat up near one of the SpaceX sats. From the ground the atmosphere would attenuate the signal too badly and you'd only have visibility for a few minutes at a time as it passes overhead maybe.

In practical terms I don't think it's a major concern. Much more likely that the spy agencies would tap the lines coming out of the ground stations.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by JumpCrisscross on Monday January 25, 2021 @03:49PM (#25908648)

> Much more likely that the spy agencies would tap the lines coming out of the ground stations

Which is a significant step backwards for e.g. Russia.

Currently, all data between Asia and North America runs on cables. Anybody can spy on those. If those data did satellite laser hops, only those with ground stations would have access. Everyone else gets locked out.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by sfblah on Monday January 25, 2021 @04:25PM (#25909131)

The company I work for changed its internal routing of data to use encryption for 100% of traffic crossing the public internet. I have to think everyone else is doing this as well. Is spying on cables like this even useful? How would ay usable data be extracted?

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by jandrese on Monday January 25, 2021 @04:29PM (#25909171)

You can learn a lot from the metadata and packet size/timing.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by anonymousiam on Monday January 25, 2021 @04:48PM (#25909402)

Military inter-satellite links deliberately choose laser wavelengths that do not propagate well through Earth's atmosphere. Such links could only be intercepted from a space-borne platform. I have no idea what laser wavelength StarLink is using, so it may not apply here.

I have no doubt that (like every other geo-mobile satellite constellation) the system allows for "port mirroring" on point-to-point links, or (more likely) relays everything through a ground station even when doing so has performance implications. This allows them to fulfill their obligation to government(s) surveillance.

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Re:SpaceX sends laser-linked Starlinks to the polar orbit by lutorm on Tuesday January 26, 2021 @12:33PM (#25918715)

If you wanted to do this, it's probably a lot easier to intercept the RF to the ground stations.

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