Low-cost Receiver Development for TDRSS DAS Sustainment and CubeSat Applications

Tracking and Data Relay Satellite System (TDRSS) Demand Access System (DAS) sustainment is aimed at modernizing the existing DAS using low-cost hardware components as well as a more robust monitor and control architecture. A key part of the system is the DAS receiver, which supports the Pseudo Noise (PN) modulation waveforms of the TDRSS. The receiver in the current DAS system is a custom design that has been increasingly difficult to maintain, due to hardware obsolescence and a lack of sufficient inventory of spare units. In addition, the receivers suffer from performance issues, which tend to limit the customer base subscribing to the DAS service. The DAS sustainment effort attempts to rectify the performance shortfall of the current receiver and address hardware obsolescence by making software portability a key design goal. As part of the DAS sustainment effort, two low-cost receivers were developed: one of them based on a commercial spread-spectrum receiver implemented on a Field Programmable Gate Array (FPGA), and the other a Software Defined Radio (SDR) implemented on a server class computer. The two receiver prototypes underwent extensive testing in a laboratory environment as well as on-air testing with orbiting customers. Receiver design details and test results are presented. The potential usages of such TDRSS compatible, low cost and small footprint of receivers in CubeSat are discussed.