4 ms·
If you want to block SAR, just set up a big corner reflector near you. It'll completely blind the part of the image near you. It would also draw a lot of atten
by leoedin 6y ago
If you want to block SAR, just set up a big corner reflector near you. It'll completely blind the part of the image near you.
It would also draw a lot of attention to you... So maybe not the best approach if you're trying to hide.
- craftinator 6y agoWell, if enough people do it... Let's make a VPN for satellite surveillance
- jusssi 6y agoBig in home decoration fashion next year, upside down pyramids hanging from the ceiling. (edit: my bad, a corner reflector would have 3 corners at the base, not 4 as a pyramid would)
- AlgorithmicTime 6y agoA pyramid is defined as any polygonal base with all vertices connected to an apex, so a triangular pyramid is possible.
- artvark11 6y agoHow big are we talking? Can I make one out of tinfoil?
- ars 6y agoAre you sure a corner reflector will work? The entire premise of the synthetic aperture is that the transmission and reception are distant from each other, but a corner reflector will reflect back to the location of the transmission - i.e. it will entirely miss the receiver.
- leoedin 6y agoYes, completely sure. Corner reflectors are used to calibrate SARs by providing fixed bright ground points. I've also seen SAR imagery where unintentional corner reflectors (in this case, a building) completely washed out the image at that location. It's true that the SAR antenna has moved a little bit by the time the transmitted signal is received. However, the signal is moving significantly faster than the satellite - with a 600km orbit, velocity is ~8km/s - so the roundtrip time is maybe 0.04s, meaning the satellite has moved 320m. That's about 0.2 degrees from the point of view of the reflector. The synthetic aperture is not just the distance covered in the round trip of a single chirp, but the distance covered during the imaging process. A SAR typically produces chirps constantly (in the tens to hundreds of Hz) and digitises the responses. All of the energy of all those responses can then be combined to form the image. If the corner reflector is in a fixed location, every chirp will have a spike in the response corresponding to that location.
- walrus01 6y agoor a whole bunch of small corner cube reflectors (such as you would see attached to a sailboat mast for intentional greater radar visibility) in a grid like array. https://www.westmarine.com/WestAdvisor/Selecting-a-Radar-Reflector https://www.westmarine.com/WestAdvisor/Selecting-a-Radar-Ref...
- dzhiurgis 6y agoWonder if someone uses this tech for monitoring entire ocean, not just narrow spots. Similarly there's monitoring of AIS by Iridium, but pirates and drug lords turn those off.