Manolis Surligas, Libre Space Foundation
Agis Zisimatos, Libre Space Foundation
Dimitris Moustroufis, Libre Space Foundation
Daniel Bita, Libre Space Foundation
Victoria Malyshkina, Libre Space Foundation
Dimitris Zournatzis , Libre Space Foundation
Manolis Surligas, Mr, Libre Space Foundation
SATNOGS-COMMS is an open-source, open-hardware communications subsystem for CubeSats, developed by the Libre Space Foundation in collaboration with the European Space Agency (ESA). This innovative system combines advanced hardware and software to meet the challenges of CubeSat missions while promoting accessibility and flexibility through an open ecosystem. Demodulation and decoding of telemetry and payload data produced by SatNOGS COMMS are fully compatible with SatNOGS ground stations. SatNOGS COMMS also integrates tightly to SatNOGS Network, supporting a mission control system for TC&C and real-time dashboards.
The COMMS transceiver operates on UHF and S-Band with two dedicated half-duplex RF frontends. The supported modulation and coding schemes are based on the CCSDS recommendations for Category A spacecrafts, with a set of user selectable framing schemes (CCSDS, IEEE 802.15.4, AX.25). The available baseband modulations are BPSK, QPSK, MSK and FSK. The supported data rates are up to 50 kbps for the UHF and up to 1 Mbps for the S-Band, depending on the modulation and coding rate used. The UHF frontend can tune from 395 up to 450 MHz, while the S-Band at 2025 – 2110 MHz for the uplink and 2200 – 2290 MHz for the downlink. Both frontends can produce up to 32 dBm of TX power and their emissions are compliant with the SFCG 21–2R4. The RX interfaces implement a custom hardware AGC mechanism and are also equipped with switchable filters (narrowband/wideband) to improve selectivity if needed. Additionally, the transceiver provides an I/Q interface for each RF frontend to extend the radio functionality and enable Cognitive Radio capabilities. To achieve this extra functionality, a ZYNQ 7020 FPGA is available in a mezzanine daughterboard form.
An STM32H7 MCU orchestrates the functional components of the COMMS transceiver, providing communication interfaces with other subsystems of the spacecraft and data storage via an on board eMMC memory. Through the MCU, SatNOGS COMMS exposes two CAN-FD, 1 SPI up to 8 Mbps and two antenna deployment interfaces supporting both GPIO and i2c deployment methods.
The bundled firmware operates based on the Zephyr-RTOS supporting over-the-air updates with multiple images and fallback mechanism, as well as asymmetrically signed firmware images, thanks to the MCUBoot bootloader. The firmware ships with a set of telecommand and telemetry responses that allow full testing of the COMMS subsystem right out of the box, utilizing the command-line utility software that accompanies the board. Command & control is also possible not only from the RF interfaces but also through the external IO interfaces (CAN, SPI) enabling easy testing and integration.
On the ground segment, each SatNOGS COMMS ground station is fully integrated into the SatNOGS Network, extended with TC&C capabilities. The SatNOGS ecosystem provides the functions for mission control, telemetry storage and viewing through a set of visualization dashboards, configurable on a per customer and/or mission basis. The mission control is based on the YAMCS software. TC&C frames are specified using the CCSDS XTCE for improved interoperability and standardization.
The entire SatNOGS-COMMS solution is open hardware and open software. The development progress, as well as various helper analysis and simulation tools, breadboard models and documentation can be found at the project repositories at https://gitlab.com/librespacefoundation/satnogs-comms