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> The satellite beams down a powerful 9.65 GHz radio signal toward its target, and then collects and interprets the signal as it bounces back up into orbit. Ye

by abeppu 6y ago

> The satellite beams down a powerful 9.65 GHz radio signal toward its target, and then collects and interprets the signal as it bounces back up into orbit. Years ago there were lots of articles about X-ray backscatter vans, owned by NYPD but probably also other jurisdictions. One of the concerns was you'd never know when they were scanning you and looking inside your car. But of course, though these active systems are invisible to human eyes, they do have to send out pretty strong signals. So I wonder if a kind of sousveillance is possible. Can we have devices that detect the signal being directed at the target, and alarm and publish that info? Both individuals could know if/when they are being imaged, and the public could see some patterns in who they look at. Anyone aware of how hard a detector would be to build?

vorpalhex 6y ago
9.65GHz would be outside the range of most common SDRs, but other than that it would be like detecting any other radio transmission. You would need a sample to know it's the satellite in question and not some other noise on that band, and it would be vulnerable to false positives unless the sample is unique.
- segfaultbuserr 6y ago
  All an SDR needs is a frontend LNA and a downconverting mixer (collectively called a LNB). Once the frequency is brought down, all standard SDRs can be used.
walrus01 6y ago
You could do this with spectrum analyzers intended for the commercial telecom industry, and a horn antenna with waveguide tuned to the right bands. It's not far off from the frequencies used in the standard FCC Part 101 licensed, 11 GHz FDD band plan for point to point high capacity microwave links. One of the problems would be that detecting such a thing in an omnidirectional way would be problematic and difficult, the horn antenna described above would have the vast majority of its gain when aimed in one particular azimuth and elevation.

by abeppu 6y ago

vorpalhex 6y ago

9.65GHz would be outside the range of most common SDRs, but other than that it would be like detecting any other radio transmission. You would need a sample to know it's the satellite in question and not some other noise on that band, and it would be vulnerable to false positives unless the sample is unique.

segfaultbuserr 6y ago
All an SDR needs is a frontend LNA and a downconverting mixer (collectively called a LNB). Once the frequency is brought down, all standard SDRs can be used.

walrus01 6y ago

You could do this with spectrum analyzers intended for the commercial telecom industry, and a horn antenna with waveguide tuned to the right bands. It's not far off from the frequencies used in the standard FCC Part 101 licensed, 11 GHz FDD band plan for point to point high capacity microwave links. One of the problems would be that detecting such a thing in an omnidirectional way would be problematic and difficult, the horn antenna described above would have the vast majority of its gain when aimed in one particular azimuth and elevation.