OnAirSatellite & navigation · Experimental
Decode CubeSat telemetry with an SDR
OnAir receives CubeSat telemetry. CubeSat telemetry from amateur satellites on 2 m / 70 cm (145.8 - 146 and 435 - 438 MHz): AX.25 at 1200 baud AFSK and 9600 baud G3RUH, GOMspace AX100 Mode 5 (ASM + Golay + Reed-Solomon) and Mode 6, CCSDS Reed-Solomon frames; callsigns, hex and ASCII dumps, satellite names from an editable table, KISS out to SatNOGS-style tools; the pass planner starts it with Doppler.
What CubeSat telemetry is
Many small amateur satellites broadcast telemetry as AX.25, GOMspace or CCSDS packets on 2 m and 70 cm. Their downlinks are open to anyone with a radio.
Frequencies and where it is used
Amateur satellites on 2 m / 70 cm (145.8 - 146 and 435 - 438 MHz): AX.25 at 1200 baud AFSK and 9600 / 4800 baud G3RUH, GOMspace AX100 Mode 5 (ASM + Golay + Reed-Solomon, GMSK 9600 / 4800) and Mode 6 (Reed-Solomon in HDLC), CCSDS Reed-Solomon (255,223) frames, all at once.
In OnAir the tuning shortcut is Satellites, 2 m / 70 cm; you can enter any frequency your radio reaches.
What OnAir shows for CubeSat telemetry
A frame log with callsigns or CSP addresses, hex and ASCII dumps, Reed-Solomon corrections, satellite names from an editable table (NORAD number, frequency, framing, callsign), KISS out to SatNOGS-style tools through the data feeds; the pass planner starts it at AOS with Doppler correction. The AX100 convolutional code and AO-40 FEC are not decoded.
This receiver is built from the published specification and checked end to end on simulated signals. It has had little or no testing on real transmissions yet, so reports and recordings on Discord are welcome.
Which radio you need
Any radio that tunes this range works. An RTL-SDR covers roughly 24 MHz to 1.7 GHz, and every other radio in the radio guide reaches it too. Antenna height and a clear view of the transmitter matter most.
Questions about CubeSat telemetry
Can I decode CubeSat telemetry with an RTL-SDR?
Usually yes for narrowband signals, as an RTL-SDR tunes roughly 24 MHz to 1.7 GHz at up to about 2.4 Msps. Wide signals such as TV channels need a faster radio, and OnAir says next to the source what the selected radio can do.
Is it legal to receive CubeSat telemetry?
Receiving satellite downlinks is generally legal. Encrypted or spread content is not decoded, and voice codecs that are patented are not shipped with OnAir.
Can I try CubeSat telemetry in OnAir without a radio?
Yes. Most modes include a built-in synthetic test signal, so you can open the screen and try the controls before you own a radio.
Try it without a radio
OnAir includes built-in synthetic test signals for most modes, so you can open this screen, see the layout and try the controls before you own a radio. The Tour button walks you through the app.