The common DPU platform for ESA JUICE mission instruments is a hardware and software platform developed by Cobham Gaisler for the scientific instrument payloads of the European Space Agency Jupiter Icy Moons spacecraft. The hardware is based around the GR712RC dual-core LEON3-FT processor with GRSPW2 SpaceWire interfaces. To accompany the JUICE instrument hardware, a flight quality SpaceWire software package has been developed, compliant with ESA ECSS standards for Space Software engineering. The software includes SpaceWire device drivers and protocol support for the SpaceWire CCSDS Packet Transfer Protocol, the Packet Utilization Standard and the SpaceWire Time Distribution protocol.

Aeroflex Gaisler has developed, under European Space Agency (ESA) contract 4000104519, a draft ECSS protocol for the transmission and synchronization of CCSDS Unsegmented Code (CUC) time in SpaceWire networks. The working name of the protocol is “Time Distribution Protocol”. Apart from transmission and synchronization of time across the SpaceWire network, the protocol also provides guidelines to achieve highly accurate time synchronization by mitigating jitter and latency affecting SpaceWire Time-Code transmission in a SpaceWire network. The protocol also provides guidelines for correcting clock drift appearing in local SpaceWire nodes. A prototype implementation of the protocol was performed and analyzed for intended functionality. The implementation of jitter and drift mitigation is based on a simple time interval measurement of incoming SpaceWire Time-Codes using local clock. Statistical information is gathered, which is then used to calculate an average correction value that is applied to modify a frequency synthesizer which provides inputs for the time generation. By controlling the frequency synthesizer the time is maintained stable without drift arising from oscillator or crystal used to generate the local clock. Distributed interrupts are used for latency measurement between two nodes in a SpaceWire network. Time-stamping of reception and transmission of distributed interrupts provides the values needed to calculate latency. The calculated latency value is used for correcting the time maintained in the system. By performing CCSDS Unsegmented Code (CUC) transmission and latency, jitter, drift mitigation a stable time keeping in a system is achieved.

The presentation will give an overview of the LEON3FT and LEON4FT processors and then show how the architectures where LEON processors are implemented have evolved from single CPU systems, to multi-core devices via the GR712RC processor and currently to the quad-processor Next Generation Microprocessor (NGMP) architecture currently being developed in activities initiated by the European Space Agency (ESA).