A Dedicated Small Satellite Approach to GNSS and SBAS

SSTL has a long history of designing and building small satellites at low cost. Recently, there has been a growing interest in applying low cost design techniques to satellites outside low Earth Orbits, for example MEO or GEO. Lessons that could be applied include a careful management of risks and performance specifications, a small team, low cost parts, and flexibility. Navigation satellites have less demanding requirements than many communications satellites and so make attractive targets for low cost satellite design. Global satellite navigation systems (GNSSs) are comprised of constellations of satellites in MEO broadcasting navigation signals. In recent years, these services have been improved by the introduction of additional space-based augmentation signals providing integrity information and differential corrections. To date, space based augmentation systems (SBASs) have broadcast signals from navigation payloads accommodated on GEO satellites. The benefits of a low cost approach to navigation satellites has been widely recognised, and SSTL has been awarded a contract to build the first demonstration GALILEO satellite, GSTB-V2/A. A brief overview and status of this mission is given in this paper. Furthermore, SSTL has performed a system design on a dedicated low cost satellite for SBAS. Two options are discussed: a bent pipe transponder similar to existing systems, and a regenerative payload more similar to GNSS signal generators.