A Spy Satellite You've Never Heard of Helped Win the Cold War

Guess that JB solar laser sat wasn't far fetched, if I'm remembering that movie (unfurling large mirror)

Even in the 1960's most Soviet radio traffic would have been encrypted. That was why the US did things like Ivy Bells (1), because they wouldn't be encrypting domestic phone traffic. (They were able to get information on Soviet missile tests, after the fact, from that source.)

And of course, as always, the easiest way to break a code is always the 5 dollar wrench attack (something like the way the Soviets paid the Walker spy ring a few thousand dollars a month to just give them the decryption keys (2)).

Finally, there is Radio MASINT that also gathers information from radio receivers, even if they are encrypted (3).

1: https://en.wikipedia.org/wiki/Operation_Ivy_Bells 2: https://en.wikipedia.org/wiki/John_Anthony_Walker 3: https://www.dni.gov/files/ODNI/documents/21-113_MASINT_Prime...

There are now commercial signit satellites. I would assume that they can track mobile devices since that would be the main market. Since everything is encrypted now, I bet they are focused on finding locations and identities of devices.

Keep in mind the purpose of these satellites often isn't to intercept the communications. A major use of ELINT to to detect and locate active radars. You don't actually care what the radar is detecting or anything like that, you are trying to identify where the radar is, what kind of radar system, maybe measure the frequency and power to get a sense of its performance, etc.

And when you are trying to actually collect communications, sometimes you can get a lot just from the metadata. Even if you don't know the content of the communications, you can know that at time T, emitter A sent a message on frequency F using protocol P, lasting for duration D and transmitting B bytes. Depending on the communication mechanism, you could also determine the intended destination as well. Even if that data is perfectly encrypted, there's a lot you can do with just traffic analysis, especially when you look at patterns over time and try to correlate this with known events.

Imagine if the US tested some classified missile over the ocean, and some unknown ship nearby broadcast something, and minutes later a bunch of encrypted transmissions are detected at various places in China, places that don't usually send communications at that particular time or that particular volume. That would be a clue that those locations are related to Chinese military intelligence. Comparing exact timestamps, and looking at what happened during similar tests in the past, you can narrow that down further.

And that's just in peacetime. In an active war, this information becomes far more useful. Anything transmitting a lot of data near the frontlines is probably something worth targetting. Maybe just an information relay point, or maybe the headquarters of an armored division. You can also look at the volume of traffic and try to discern intentions. A big spike in the amount of communications in a particular region, followed by near radio silence? That's probably the start of an offensive.

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