Advancements in hardware design for the frontier radio used for the solar probe plus mission

The Frontier Radio for the Solar Probe Plus mission offers a host of hardware design and manufacturing improvements. These improvements build on the technology readiness level (TRL)-9 radio platform that was flown on the Van Allen Probes mission in a duplexed S-band configuration and several development tasks funded by NASA Headquarters. Prior RF slice designs consisted of two separate circuit boards: one for lower frequencies and one for high-frequencies; advances in technology enabled the use of a high-frequency multilayer laminate with highly integrated miniature components to create a single circuit board, thereby simplifying manufacturing. This change also enabled an improved circuit topology in the upconverter in both exciters producing lower phase noise and better I/Q modulation accuracy. RF shielding performance was improved using compartmentalized plates and Spira-Shield gaskets. Use of a magnesium alloy for the slice packaging reduced the overall radio mass. A design-variant approach was implemented to facilitate flexibility and re-configurability across multiple missions and applications. For example, one circuit board artwork supports S, X, and Ka-band configurations of the exciter slice, and the digital signal processing (DSP) slice's board artwork facilitates numerous alternate configurations for a variety of mission applications. Advances made to the DSP slice include dual footprint circuits and an interposer for the field programmable gate array (FPGA) to minimize layout changes, a change to a radiation-hardened magnetoresistive random access memory (MRAM) to replace the programmable read-only memory (PROM), and new test and debugging circuits including a serializer-deserializer (SERDES), a SpaceWire debug link, and small footprint soft-touch connectors to access internal signals. A multi-chip module (MCM) was qualified for use in space that converts X-band to Ka-band and I/Q modulates directly at Ka-band. This enables a first for a deep-space mission: primary science data downlink with simultaneous data and navigation over Ka-band. Manufacturing techniques such as the use of a pick-and-place machine with part value validation, standardized circuit board sizes, and fewer overall circuit boards to integrate all contributed to faster and more reliable hardware assembly. The flight radio hardware is fully fabricated and has completed proto-flight testing for a planned 2018 spacecraft launch.