CoCom regulations and GPS receivers for balloons and cubesats (2016) | Hacker News Reader

CoCom regulations and GPS receivers for balloons and cubesats (2016)

space.stackexchange.com

23 pointsvinnyglennon14 comments

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?

Nah, I live in a major city between two airports, under an airplane departure and a heli route. I can't really launch rockets or balloons from my home.

When I was at uni I didn't have the funds for this hobby unfortunately.

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.

[2016]

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