A Spacecraft Computer Repairable via Command

The MULTIPAC is a central data system developed for deep-space probes with the distinctive feature that it may be repaired during flight via command and telemetry links by reprogramming around the failed unit. The computer organization uses pools of identical modules which the program organizes into one or more computers called processors. The interaction of these modules is dynamically controlled by the program rather than hardware. In the event of a failure, new programs are entered which reorganize the central data system with a somewhat reduced total processing capability aboard the spacecraft. As an example of one MULTIPAC configuration, a 16-watt system with 12 288 words of memory would have extensive data processing capability for variable data formatting, data sampling, converting analog information from experiments, and performing data reduction on experimental data to improve information transfer on a limited capacity telemetry channel. Emphasis is placedon the evolution of the system architecture and the final overall system design rather than the specific logic design.