Protocol Controller Configurations for Self-checking Processor Pair for long orbital missions

Abstract

Orbital space missions lasting for a long duration require a robust computing system that can withstand extreme environments, especially high levels of ionizing radiation. A self-checking pair based on an indigenous processor is proposed as the onboard computer to provide radiation tolerance. The 1553B bus is commonly used for communication in space systems. The protocol functions in the onboard computers are carried out by a separate protocol control chip. As the outputs from only one processor are routed to the bus, the processors in the pair can be configured in two ways – either both as bus controllers or one as bus controller and one as bus monitor. The 1553B protocol controllers in the processor pair were initialized as per this requirement and the complete software was burned into the program memory in a prototype board. Simulation runs with standard flight inputs proved that the final outputs produced in both the cases match exactly. Based on the results and further analysis, it was decided to opt for the BC-BM configuration.