GNU Radio for Space (and Aircraft)

GOMX-3 is a CubeSat with several payloads. One of them is a software defined radio configured to read ADS-B signals sent by commercial aircraft. The idea is that a satellite can monitor aircraft over oceans and other places where there no RADAR coverage. ADB-S transmits the aircraft’s ID, its position, altitude, and intent.

The problem is that ADS-B has a short-range (about 80 nautical miles). GOMX-1 proved that the signals can be captured from orbit. GOMX-3 has more capability. The satellite has a helical antenna and an FPGA.

The people behind the satellite, GomSpace, has a complete parser for the ADS-B data beacons and [destevez] has it rolled into a GNU Radio module. There’s a good representation of captured data on a map in [destevez’s] blog post. If you want something less interactive, you can see a static map of all collected data. If you want to try your hand at picking up GOMX-3, you can hear it transmitting in the video below.

We’ve talked a lot about CubeSats in the past and ADS-B monitoring (the link is broken, but the video still works). If you want a GNU Radio primer, we’ve done that, too.

10 thoughts on “GNU Radio for Space (and Aircraft)

    1. Distance has a lot to do with aircraft elevation, and with obstructions such as trees and buildings. Line-of-sight can go a long way under suitable conditions. 80 nautical is for reliable and repeatable operation in most weather conditions. That is why a satellite works so well for ADS-B reception — no LOS obstructions and no nearby EMI interference. It may also depend on relative antenna orientations between the aircraft and your receiver. Perhaps a helical antenna such as used on the cubesat may give you even further distance to (some, but not necessarily all) aircraft.

      1. Indeed, ADS-B signals have plenty of power. A satellite should have a very large line-of-sight range. However, the 1090MHz ES downlink is saturated in most areas with a busy airspace. A sat might thus require quite a bit of DSP to get useful results.

  1. A quick look around das webs suggests that ADS-B antennas are often mounted on the bellies of airplanes. Bearing in mind the difference in altitude, the satellite would almost *need* to be a few hundred km downrange for the body of the aircraft to not be directly in the signal path.

  2. Isn’t there something called ADSB-C that is the satellite uplink from planes? I read somewhere someone tapped in to the C-band downlink and cracked the protocol with the help of a low cost SDR.

  3. I have an ADS-B set-up that has a home made co-linear antenna made out of semi-ridged feeding a high pass filter and a good LNA that’s mounted about 20 feet up on the eave of my house with a cheap SDR dongle at the PC end and I’m getting over 200NM out of high altitude planes. I bet if I had everything in the RF string at the antenna and then fed the USB portion down from the eave, I could really reach out there.

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