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So a satellite was found to be jamming GPS even though that wasn't its apparent purpose.
This is the most powerful counter to satellite navigation purposes that exists, as I already wrote in Twitter.
The problem isn't the very weak signal of such jammers; it's that they're overhead. The best method for filtering jamming signals out is to ignore the signals on satellite navigation frequencies that are coming from the ground. You can do this with multi-antenna setups if you can tolerate their size:
https://militarnyi.com/en/news/new-chinese-crpa-antenna-found-on-russian-shahed/
It's similar to the HF direction finder HF/DF from WW2: A radio wave coming from the right takes longer to an antenna to the left than to the right. The time lag can be used to identify the direction with a passive receiver. That's how passive radio direction-finding works, including radar warning receivers.
A jammer that's overhead just like the real satellite navigation service satellite defeats this.
Moreover, you can bring hundreds or thousands of tiny and really cheap satellites into low earth orbit with one-time pad encrypted communication with base station and that communication can be limited to overflights of your territory only (and from below). This almost guarantees nobody is going to mess with your control over such a fleet of jamming satellites. The jamming could be limited to certain areas, albeit those would almost necessarily be hundreds of kilometres wide.
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There are alternatives to GPS. eLORAN is viable, but given up on. New advanced inertial measurement tech approaches satellite navigation accuracy, but is still low in technological readiness level. Large fleets of low earth orbit satellites such as Starlink's fleet can substitute for satellite navigation and at least match the jammers in signal strength, but legacy fleets may depend on satellite navigation themselves and legacy fleets don't use the frequencies that legacy satellite navigation receivers depend on.
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So what can be done about the jamming by satellite if we cannot cheaply or quickly replace legacy satellite navigation?
We can shoot down satellites, but that causes much debris in orbit and it costs millions per shot while the jammer may be a cheap cubesat.
We should technically be able to defeat at least low earth orbit jammer satellites with high-powered lasers. We need the satellite tracking and passive radio frequency direction finding to discern which space object is jamming, track it, wait for an opportunity where no other non-hostile satellite would be affected and destroy it. The required power would necessitate quite large lasers and it would only be possible with clear sky - which is rare over Central Europe in wintertime, but the orbit would also lead over Australia's outback, Djibouti, Greek mountains, Spain's inland and Alps mountains. The problem is the required power of many megawatts. We'd likely have to combine a cluster of multiple lasers on one target to at least gain the laser ablation effect. A space-based weapon would be very expensive, centralised and thus be targeted itself. A Spanish or Australian site would be fairly safe, especially if protected by decoys, chaff projection in case of IRBM/SLBM attack and satellite navigation jamming itself. The same ground-based lasers could be used to deal with hostile earth observation satellites and even deal warning shots to non-hostile earth observation satellites of companies or governments that relay the data to hostiles. Another problem remains; satellite and generally space object tracking radars are big, expensive, stationary (other than those on ships) and could be targets to conventional-tipped IRBM/SLBM attacks if no others.
https://x.com/TheDeadDistrict/status/2063629144626225220?s=20
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