Software Defined Radio Based Communications Subsystem for C3 Ground Control Station

This thesis results from activities conducted within the ¿C3¿ project of the ¿CubeSat Team¿ of the Polytechnic University of Turin. Goal of work is to implement Communication Subsystem of CubeSat Control Centre, based on software defined radio paradigm. CubeSat concept was proposed to set standards to promote developing required skillsets in students and novice researchers engaged in the aerospace industry. However, CubeSat concept has quickly been adopted to fulfill the needs of various commercial and research fields as well. Involvement of Polytechnic University of Turin in the educational satellite field started in 2004, and it already launched E-ST@R-I and E-ST@R-II CubeSats to the orbit in 2012 and 2016, respectively. Their ground control operations have been conducted by partnering amateur radio stations, however in order to have in-house capability to control current and future CubeSats and to have the competence to support more advanced mission requirements, ¿CubeSat Team¿ of the Polytechnic University of Turin has launched a project to build its first ¿CubeSat Control Centre¿ - ¿C3¿. ¿C3¿ is a ground segment for CubeSat missions, which aims to incorporate capabilities of traditional amateur radio stations and to enhance their potentials by using recent advancements in software radio. However, unlike conventional amateur radio stations, which primarily operate on VHF/UHF bands and rely on traditional amateur radio hardware, C3 also has capability to operate on S and X bands as well, and its architecture incorporates software radio concept to maximize its flexibility to support different mission requirements. In addition, ability to operate autonomously is one of the core qualities of C3. This thesis work aims to implement the Communication Subsystem of ¿C3¿, which substitutes Terminal Node Controller and radio hardware components of traditional amateur radio stations, and operates on the first and second layers of OSI/ISO. Communication Subsystem conducts operations to receive telecommand/telemetry packets from Mission Control Software, modify/encapsulate them in proper packet format, modulate them in required modulation format, and transmit final waveform to RF front-end. Reverse operations for downlink are also covered. Although several open-source implementations already deal with mentioned parts for downlink operations of amateur radio CubeSats, they either lack capability to perform uplink operations, or they need to be ported to C3 architecture. In this thesis work, uplink and downlink chains of CubeSat communications are implemented within C3 architecture, using GNU Radio as the main DSP environment. Test phase has been conducted via demonstrating communication chains of E-ST@R-II and NOAA type of satellites. Possibilities to embed autonomy and adaptivity of software to comply with different encoding and modulation schemes to proposed Communication Subsystem architecture are also explored