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
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...
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...
> 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
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.
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.
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
Have you done that?
I have. It works.
Used a huge amount of compute though and takes a long time to get a fix.
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...
Nearly all commercial GPS receivers use a 1 bit ADC. Ie. Just a comparator.
The sample rate isn't high either - 16Mhz IIRC.
Maybe that's why nobody else does
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.
Have you done that?
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
CoCom 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
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.
Have fun. https://github.com/gnss-sdr/gnss-sdr
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.
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