Design and implementation of a Software Defined Radio telemetry receiver for GEO satellites

The thesis has been carried out in the TT&C (Telemetry Tracking and Command) department of Telespazio company, at Fucino Space Center, with the goal of developing an SDR (Software Defined Radio) receiver able to process telemetry signals coming from in-orbit satellites. The project has been realized exploiting a National Instruments USRP (Universal Software Radio Peripheral) as hardware support, in particular the USRP-2920, and the free and open source ecosystem GNU Radio for software development in the form of signal processing blocks. The SDR approach is becoming increasingly popular in the field of communication systems thanks to its high level of flexibility, easy reconfigurability and reduced cost. Today, software defined radios are employed in radio astronomy, digital video broadcasting, commercial applications like spectrum monitoring and in the TT&C field to interface the satellite for telemetry and command activities. The implemented receiver is able to work with both modulations generally adopted for satellite housekeeping telemetry, i.e. residual carrier modulation used for low rate telemetry, e.g. PCM/PSK/PM, and suppressed carrier modulation used for high rate telemetry, e.g. QPSK. With regard to decoding, instead, only convolutional and Reed-Solomon coding schemes have been implemented since they are the most popular for satellite telemetry signals. The first part of the receiver design is focused on Matlab simulations, that resulted to be useful to properly design the receiver according to different modulations and coding schemes, and also to evaluate performance in terms of BER vs. Eb/N0. Successively, following the structure of the simulated receiver, GNU Radio software blocks have been set and the resulting flowgraph has been tested on simulated telemetry signals in order to validate the system. Finally, the product has been used to receive telemetry from MTG-I1 (Meteosat Third Generation - Imager 1), the first launched satellite of the MTG program of ESA (European Space Agency) and EUMETSAT (European Organization for the Exploitation of Meteorological Satellites) for the improvement of weather forecasting. For this purpose, an S-band antenna made available by Telespazio has been pointed toward the mentioned GEO (Geostationary Orbit) satellite, intercepting the RF signal that has gone through the RF chain before reaching the USRP-2920. After demodulation and decoding, recovered telemetry frames have been time-stamped before being sent to the SCC (Satellite Control Center) in order to analyze the status and the health of the spacecraft. Although the system has shown a remarkable capability of processing low rate telemetry coming from GEO satellites, further enhancements in terms of software optimization and protocol implementation for the interface with the SCC are planned in the near future, in a way to have a product to be used for TT&C purpose aiming to replace the commercial BBUs (Baseband Units).