gr-satellites is a GNU Radio out-of-tree module encompassing a collection of telemetry decoders that supports many different Amateur satellites. This open-source project started in 2015 with the goal of providing telemetry decoders for all the satellites that transmit on the Amateur radio bands.

It supports most popular protocols, such as AX.25, the GOMspace NanoCom U482C and AX100 modems, an important part of the CCSDS stack, the AO-40 protocol used in the FUNcube satellites, and several ad-hoc protocols used in other satellites.

This out-of-tree module can be used to decode frames transmitted from most Amateur satellites in orbit, performing demodulation, forward error correction, etc. Decoded frames can be saved to a file or displayed in hex format. For some satellites the telemetry format definition is included in gr-satellites, so the decoded telemetry frames can be printed out as human-readable values such as bus voltages and currents. Additionally, some satellites transmit files such as JPEG images. gr-satellites can be used to reassemble these files and even display the images in real-time as they are being received.

gr-satellites can be used as a set of building blocks to implement decoders for other satellites or other groundstation solutions. Some of the low level blocks in gr-satellites are also useful for other kinds of RF communications protocols.