Mysteries in polar orbit – space's oldest working hardware keeps its secrets | Hacker News Reader

Mysteries in polar orbit – space's oldest working hardware keeps its secrets

theregister.com

73 pointsLorenDB9 comments

Uncensorable-even-in-principle satellite communication is such an nice ideal. The analog repeater had no idea what it was re-broadcasting, and even in principle couldn't make any QoS distinctions, or censorship, given the technology then available.

I'm not sure it's possible to be uncensorable in principle. If you can't make QoS decisions, you can't distinguish jamming from normal activity. Jamming then becomes the means of censorship. If you monitor your target's transmissions, you can jam only when they're transmitting, allowing targeted censorship. (The technical difficulty involved may be sufficient to be uncensorable in practice. Your threat model may vary. My issue is with whether this is possible in principle.)

It's sort of like the how the paradox of tolerance limits how much freedom of speech is possible, in that if you allow some to intimidate others into silence, you end up with emergent limitations on speech that are actually more restrictive than disallowing intimidating speech. So a commitment to free speech leads one to implement moderation or censorship to some degree (and conversely, a commitment against any moderation or censorship becomes an implicit acceptance of other people placing limitations on speech).

I think it's interesting that there seems to be a connection between these principles in very different domains.

Given we are talking about jamming a repeater in a rather extreme orbit, you have to account for the speed of light delay. By the time a bad actor gets news that a message they don't like is being transmitted and starts up the jammer the broadcast may already be over (assuming its a data transmission that comes in bursts of packets)

Nothing really prevents continuous jamming the whole time it's overhead for an area you care about. All a government needs to do is broadcast noise at a high power on the band(s) of interest to completely drown out dissident signals.

That's a very good point. I suppose that, if we assume a bitrate, and we assume partial messages are irrecoverable, then this puts a limit on the "uncensorable bandwidth." But it's easy to imagine a protocol that splits large messages into very small pieces to so that each message is below that limit.

I know a lot of older communications satellites (incl. commercial ones) were just dumb repeaters - receive a signal on one frequency, retransmit it in real time on a different one, don't need to decode it or authenticate anything (although you still need the specialized radio transmitter hardware). This is how Captain Midnight [0] was possible.

I can't imagine modern satellites work the same way.

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

"Bent pipe" dumb repeaters are still common for geostationary satellites, AFAIK. Being future-proof against anything except spectrum reallocation (modulation and protocol upgrades can be implemented just by changing equipment on the ground) is valuable for things with long lifespans and high replacement costs.

Fortuitous time for me, having just come back from the European Space Tech Expo. When I was just starting out in the satellite industry, the more experienced engineers used to talk about OSCAR-7 with such reference. Amazing that it is still going, and a testament to the amateur radio community.

https://en.m.wikipedia.org/wiki/AMSAT-OSCAR_7

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