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Nobody's talking about what might cause an outage. There are three basic parts to any GNSS: The control segment, the space segment, and the atmosphere on the wa

Nobody's talking about what might cause an outage. There are three basic parts to any GNSS: The control segment, the space segment, and the atmosphere on the way back down. The control segment is run by the military so let's assume it's as secure as any other military network, and that attacking it would be seen as an act of war. And there are several constellations run by various countries, who do not represent a common target. The space segment is vulnerable to space weather, but has proven pretty darn resilient so far. Even if a big CME or something knocked out a few satellites, there are ton of them up there, and most of the most critical applications only rely on timing, not positioning, and would work fine with a degraded constellation. The atmosphere is where it gets interesting; an airburst nuke will make the ionosphere basically opaque to such signals for quite some time. How long depends on a lot of details, but assume several weeks. This would affect all signals from all constellations for all users, and is IMHO the only threat worth worrying about. Because an airburst over the ocean might not be construed as an attack on any specific nation, but it would exact a huge economic toll on the most developed and tech-reliant nations. It must be a tempting option for a spastic tyrant who has a nuke or two and feels backed into a corner.

Jonnax 7y ago
What about space debris? Isn't there a non zero chance that a satellite could hit some debris and cause a chain reaction?
- gingabriska 7y ago
  Isn't there enough redundancy in space that one sat going down means nothing for the system
  - xvector 7y ago
    No, the issue with space debris is that we are quickly approaching the point where a single unfortunately placed collision could chain using a sort of exponential “shotgun effect”, destroying virtually all satellites at a given orbit and rendering space travel impossible for decades if not centuries, setting human space exploration back significantly as launches have to deal with thousands of metal shards traveling at tens of thousands of mph. See this video[1] by Kurzgesagt: “End of Space - Creating a Prison for Humanity.” [1]: https://youtu.be/yS1ibDImAYU https://youtu.be/yS1ibDImAYU
- akiselev 7y ago
  Space debris is largely an issue for low earth orbit, through will all space activity has to pass through and is a pretty tight orbit. GPS satellites are in geosynchronous orbit which is over 30,000km from the surface of the earth so there is much more volume of open space, making debris a much smaller risk (for the same amount of debris, since 600^3 << 30,000^3).

Jonnax 7y ago

What about space debris? Isn't there a non zero chance that a satellite could hit some debris and cause a chain reaction?

gingabriska 7y ago
Isn't there enough redundancy in space that one sat going down means nothing for the system
- xvector 7y ago
  No, the issue with space debris is that we are quickly approaching the point where a single unfortunately placed collision could chain using a sort of exponential “shotgun effect”, destroying virtually all satellites at a given orbit and rendering space travel impossible for decades if not centuries, setting human space exploration back significantly as launches have to deal with thousands of metal shards traveling at tens of thousands of mph. See this video[1] by Kurzgesagt: “End of Space - Creating a Prison for Humanity.” [1]: https://youtu.be/yS1ibDImAYU https://youtu.be/yS1ibDImAYU
akiselev 7y ago
Space debris is largely an issue for low earth orbit, through will all space activity has to pass through and is a pretty tight orbit. GPS satellites are in geosynchronous orbit which is over 30,000km from the surface of the earth so there is much more volume of open space, making debris a much smaller risk (for the same amount of debris, since 600^3 << 30,000^3).