On-board data compression of geophysical data

Instruments on scientific satellites are frequently capable of generating vastly more information than the telemetry sub-system can transmit to the ground. The technique to overcome this problem, and one which the authors anticipate using for the ESA CLUSTER mission, is to incorporate some intelligence in the instrument. This intelligence can then be used for data compression, data selection and event selection. The authors report on some progress with (mainly) the first two of these concepts. The value of the data compression approach is limited by the acceptability of any degradation to the data. For plasma wave receivers an uncertainty of 3 dB in the measurement is usually acceptable. It is concluded that data compression is a useful technique which will generally give a saving of around 80%