A high-performance, compact software-defined radio designed to operate in Low Earth Orbit (LEO) environments. The Cesium SDR-1001 includes four receive channels, four transmit channels, and a state-of-the-art FPGA in a credit-card-sized footprint. The module is suitable for demanding digital signal processing and communications applications. Use as a stand-alone SDR or combine with other Cesium modules for a complete bits-to-photons solution.