Sheffield team interests Keith Yearby, Michael Balikhin

Current and previous space missions The Sheffield team provided the DWP instrument for the Cluster Wave Consortium, still operating after almost 12 years in space. The DWP handles commanding and control for all consortium instruments, and telemetry data handling for all except Wideband data. The DWP is particularly closely involved with the operation of Whisper the relaxation sounder. The Sheffield team coordinates the operations of the Wave consortium. Similar DWP instruments were provided for the MARS96 ELISMA consortium and Double Star TC1 spacecraft. All current instruments are based on the Inmos Transputer, a 16 bit micro-processor including 4 serial links. The MARS96 instrument in particular exploited the transputer links to implement a fault tolerant multi-processor design. The Transputer itself is now obsolete, but the links evolved to become IEEE 1355 and then SpaceWire. The Double Star instrument added a low frequency direct sampling receiver (3 * 10 kHz, 14 bit) and spectrum analyser software.

Current instrument developments The receiver and analyser of the Double Star DWP instrument have been implemented in a Xilinx FPGA using several alternative architectures (Power PC, MicroBlaze, and LEON3). This provides around 30x processing speed improvement over the transputer, for less power. Existing research on radiation tolerant programming of Xilinx FPGAs has been reviewed. The high rate of single event upsets in the configuration memory is a particular concern. While techniques exist to mitigate these, the overheads and complexity required to produce a dependable design mean that Actel FPGAs or ASICs are often preferred. However, for a front end processor performing simple repetitive tasks under the supervision of a main processor, the higher speed, lower power and reconfiguration ability of the Xilinx devices are a considerable advantage. A study has been performed on the disturbance of the spacecraft potential resulting from the operation of the relaxation sounder (Whisper) on Cluster. It should be possible to substantially reduce the disturbance by modifying the sounding waveform (cosine window plus DC offset).

Scientific Interests Observations of ducting of Chorus waves, using Cluster wave data, electron density and spacecraft potential. Observation of Chorus waveforms and propagation, using Cluster EFW internal burst data.

Possible Contributions to RPWI To attract funding the team’s contribution should be associated with a specific scientific data product. Based on our previous experience and interests, we could contribute to RPWI in the following areas: Control and signal processing for Mutual Impedance Measurements. Software/HDL for wave analysis. Direct sampling receiver.