Some Methods for the Compression of Binary Data in Spacecraft Experiments

A number of methods for compressing binary data on board spacecraft are discussed. Five systems, ranging in complexity from the simple use of prescalers to a floating point system, are described. The systems are compared, assuming that an accumulated count must be read into an eight bit telemetry word. Maximum count, reading error and hardware complexity are examined for each system. General formulae are presented which allow the calculation of maximum count for each system assuming that N bit telemetry words are available. The effect of a larger telemetry word on the performance of some of the systems is examined.