Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

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

space.stackexchange.com

Post reply on HN
Print view View original

11–16 of 16 posts

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

#11

Post by minetest2048 »

inigyou wrote: post #5
londons_explore wrote: post #4

Earlier quoted context omitted.

I have. It works. Used a huge amount of compute though and takes a long time to get a fix.

Maybe that's why nobody else does

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

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

#12

Post by londons_explore »

minetest2048 wrote: post #10
londons_explore wrote: post #4

Earlier quoted context omitted.

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.

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

#13

Post by inigyou »

rescbr wrote: post #9
inigyou wrote: post #5

Earlier quoted context omitted.

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?

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

#14

Post by holgerschurig »

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.

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

#16

Post by rescbr »

inigyou wrote: post #13
rescbr wrote: post #9

Earlier quoted context omitted.

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.

Post reply on HN