4 ms·
CoCom regulations and GPS receivers for balloons and cubesats (2016)
- awesomeusername 3mo agoSeems fairly useless to me, for a few dollars I can sample the L1 frequency with a dumb device which has no idea of speed or altitude, and do the calcs with FOSS which is in the wild. Basically a rule which inconveniences the honest and has zero impact on the bad dudes, whoever they are
- inigyou 3mo agoHave you done that?
- londons_explore 3mo agoI have. It works. Used a huge amount of compute though and takes a long time to get a fix.
- inigyou 3mo agoMaybe that's why nobody else does
- rescbr 3mo agoYou can use a FPGA, like this 2013 project: http://www.aholme.co.uk/GPS/Main.htm http://www.aholme.co.uk/GPS/Main.htm Or go old school (1991-1992): https://lea.hamradio.si/~s53mv/navsats/theory.html https://lea.hamradio.si/~s53mv/navsats/theory.html So yeah, this regulation is absolutely an inconvenient measure.
- minetest2048 3mo agoThere's a strong indication that SpaceX does use software receiver in Falcon 9 and Starlink: when they didn't encrypt the downlink telemetry someone captured the signal and found some plain text: https://www.rtl-sdr.com/receiving-space-x-falcon-9-telemetry-with-a-hackrf-and-1-2m-satellite-dish/ https://www.rtl-sdr.com/receiving-space-x-falcon-9-telemetry... That plain text looks like what a software GNSS receiver outputs as its very verbose, and this paper: https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10/Nichols_ION_GNSS_2022.pdf https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10... , a paper about a software receiver mentioned this: > PpRx has been licensed through the Radionavigation Lab to multiple commercial companies, but notably a major aerospace company that uses the technology across their suite of advanced spacecraft and satellites. The SDR is deployed across the company’s mega-constellation of satellites used for broadband Internet
- minetest2048 3mo agoFor L1 I think a raspberry pi can have a reasonably fast time to first fix, for offline processing you can go faster than real time. L2/L5 need large sampling rate and a pi is probably not fast enough.. unless if you ditch float32 processing and do 2 bit signal processing, a uni commercialized that: https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10/Nichols_ION_GNSS_2022.pdf https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10...
- londons_explore 3mo agoNearly all commercial GPS receivers use a 1 bit ADC. Ie. Just a comparator. The sample rate isn't high either - 16Mhz IIRC.
- AlphaWeaver 3mo ago[2016]
- ronsor 3mo agoHave fun. https://github.com/gnss-sdr/gnss-sdr https://github.com/gnss-sdr/gnss-sdr
- angry_octet 3mo agoIt's important to note that this is in relation to real time position estimation. You can collect the signal measurements and process offline later for telemetry reconstruction.
- holgerschurig 3mo agoCoCom was terminated in 1994 and is entirely irrelevant by now (IANAL and all that) What we have now is https://en.wikipedia.org/wiki/Wassenaar_Arrangement https://en.wikipedia.org/wiki/Wassenaar_Arrangement Fun fact 1: Switzerland (a major provider of GPS chips via u-blox) never signed or ratified CoCom. But they still followed it mostly, for fear of retaliation. They even had an allowance of "sell list 1 goods for up to 35 million Schweizer Franken" that they never reached, they only went up to 8 million Schweizer Franken. They however are a member of Wassenaar. Fun fact 2: Russia is a member of Wassenaar. But I guess they now give a shit on it and give to North-Korea whatever NK wants, for all of these nice North Korean cannon fodder soldiers.
- deleted 3mo ago[deleted]