CoCom regulations and GPS receivers for balloons and cubesats(space.stackexchange.com)

19 pointsby vinnyglennon7 hours ago4 comments

awesomeusername6 hours ago
Seems 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
- inigyou5 hours ago
  Have you done that?
  - londons_explore5 hours ago
    I have. It works.
    Used a huge amount of compute though and takes a long time to get a fix.
    minetest2048an hour ago
    For 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...
    inigyou5 hours ago
    Maybe that's why nobody else does
    minetest2048an hour ago
    There'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...
    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... , 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
    rescbr2 hours ago
    You can use a FPGA, like this 2013 project: http://www.aholme.co.uk/GPS/Main.htm
    Or go old school (1991-1992): https://lea.hamradio.si/~s53mv/navsats/theory.html
    So yeah, this regulation is absolutely an inconvenient measure.
ronsor3 hours ago
Have fun. https://github.com/gnss-sdr/gnss-sdr
angry_octet3 hours ago
It'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.
AlphaWeaver4 hours ago
[2016]