Space-based Earth observation and scientific instrumentation currently under development will push the limits of on-board data-handling technology. In the past Mil-Std 1553 and proprietary data-links were used to get instrument data from the instruments to the on-board mass memory unit and to the down-link telemetry system. Over the past decade the proprietary data links have been replaced with a standard networking technology designed for use on-board spacecraft: SpaceWire. While SpaceWire is currently being used to fulfil the on-board data-handling requirements of many missions, there are some very high data-rate instruments which are beyond its capabilities.Several future space-based instruments, for example synthetic aperture radar (SAR) and hyper-spectral imagers, will be capable of producing data at data rates of several Gbits/s. New downlink telemetry techniques will be able to provide much higher downlink capacity than previously possible. High speed memory technologies will be able to serve multiple high data rate instruments and stream data to ground on demand. To support the growing demand for onboard communications network bandwidth, technologies able to support multi-Gbits/s data transfer have been developed, unfortunately these are all restricted USA devices resulting in a critical European dependency.ESA has been developing a standard multi-Gbits/s network technology called SpaceFibre. At present this important ESA technology is dependent upon the USA for the radiation-tolerant physical layer devices. The SpaceFibre-HSSI project plans to integrate two or more complete SpaceFibre interfaces together with the physical layer devices in a single radiation tolerant ASIC manufactured by a European foundry. Not only will this alleviate the dependency on very high-speed serial interface devices, it will provide a complete SpaceFibre solution in a single chip, and develop an essential European radiation-tolerant ASIC fabrication capability.