Evolution of the Malfunction Isolation and Recovery Methodology for Canada's Mobile Servicing System (MSS)

The Mobile Servicing System (MSS) is Canada’s contribution to the International Space Station (ISS). The MSS is one of many systems that support the operation of the vehicle and use the vehicle’s resources and utilities to function. The operators on the ground and on board the spacecraft use malfunction procedures, or “Mals”, to respond to anomalies observed within the vehicle’s systems. These procedures, based on detailed analysis of the system’s design and its observed behavior, allow the crew to ascertain what has failed, determine what functionality remains, and reconfigure the system to proceed with operations. Specific Mals are executed based on the malfunction signature that is displayed to the operator, as well as the operational scenario during which the