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If you think thats cool, MIT students have been making Synthetic Aperture Radar (which uses "chirps" of radio waves and measures the time of flight) for the pas
by hwillis 12y ago
If you think thats cool, MIT students have been making Synthetic Aperture Radar (which uses "chirps" of radio waves and measures the time of flight) for the past few years, with enough resolution to image groups of push pins. Oh yeah, and it works through walls. Radar can seem like a black art but simulation software and a bit of knowledge makes simple stuff like this perfectly doable.
http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-system-capable-of-sensing-range-doppler-and-synthetic-aperture-radar-imaging-january-iap-2011/ http://ocw.mit.edu/resources/res-ll-003-build-a-small-radar-...
- toomuchtodo 12y agoI think its awesome that GPS is regulated (Speed or Altitude) with export controls, but you can build high-quality, weapons-grade SAR at a college. The future is incredible.
- trhway 12y agocool footnote there: "This work is sponsored by the Department of the Air Force under Air Force Contract #FA8721-05-C-0002." well, you can build high-quality un-locked GPS receiver as a DIY too :) http://www.aholme.co.uk/GPS/Main.htm http://www.aholme.co.uk/GPS/Main.htm
- toomuchtodo 12y agoWhen that link first hit HackerNews I thought, "There are some incredible people out there doing cool stuff".
- hwillis 12y agoHah, there's a lot more to weaponized/spy SAR than just the radar; you have to have very good measurements of your movement as you record. It can be improved algorithmically as well but data is king
- InclinedPlane 12y agoWell, funny story. When North Korea put up their first satellite it used GPS. Which, when you think about it, is pretty funny because denying entities like the North Korean regime use of GPS in that use case is a major reason the export controls exist.
- toomuchtodo 12y agoWhich is very funny, as they could've used celestial navigation systems/star trackers (which are impossible to deny them from using) similar to that used with ICBMS. http://en.wikipedia.org/wiki/Attitude_control#Star_tracker http://en.wikipedia.org/wiki/Attitude_control#Star_tracker http://www.ballaerospace.com/page.jsp?page=104 http://www.ballaerospace.com/page.jsp?page=104 I've always thought star trackers would make wonderful backups to GPS for high-altitude aircraft (they work even during daylight hours depending on atmospheric conditions).
- vonmoltke 12y agoThe P-3C Orion is fitted with a retractable sextant. Pre-GPS it was a primary navigation aid, but has been maintained post-GPS as an emergency system in case GPS fails. I don't know offhand of its replacement, the P-8 Poseidon, has any kind of celestial navigation system as a backup, but I would not be surprised if it did.
- matthewmcg 12y ago"depending on atmospheric conditions" is a big IF in the polar regions. A USAF U-2 on a high altitude polar air sampling mission accidentally wandered into Soviet airspace at the height of the Cuban missile crisis because auroras blocked the pilot's stellar fixes. See: http://www.vanityfair.com/politics/features/2008/06/missile_crisis_excerpt200806 http://www.vanityfair.com/politics/features/2008/06/missile_...
- toomuchtodo 12y agoHave we come far enough yet with mapping the earths magnetic field that you could use it to cross check your location with the star tracker's data?
- wglb 12y agoHowever, export might be a different story.
- toomuchtodo 12y agoPut the PCB board plan online, and it can be built/printed at almost any PCB fab shop. Goodbye export controls. Its PGP all over again, just with atoms instead of bits.