Satellite reliability requirements: Effect of transportation system, sparing and maintenance strategies

Abstract

Mission requirements are frequently specified in terms of required sensor availability over a specified mission duration. Availability is the probability that at least a specified number of sensors will be operational when required. The objective is to design, develop and select that system which minimizes the present value of life cycle cost (and risk) and satisfies mission requirements, including sensor availability. Since sensor availability is a function of overall satellite configuration (including redundancy), sparing and maintenance strategies, and transportation system reliability, standdown time when failures occur, and availability, it is necessary to consider the many complex interrelationships that exist when configuring a satellite. In fact, satellite design characteristics should be established by considering the interactions of satellite configuration, sparing and maintenance and transportation system alternatives. This paper deals with the effect that alternative sparing and maintenance strategies and transportation systems have on the requirements that must be imposed upon satellite subsystem reliability. The Satellite Cost and Availability Model, SATCAV (which is used to perform the analysis) is briefly described and examples are presented that indicate the influence that transportation choice, sparing and maintenance strategies have on the requirements that must be imposed on satellite design parameters in order to meet availability constraints. Typical relationships are developed between availability and life cycle cost as a function of sparing strategy, transportation system and satellite reliability characteristics, and other pertinent parameters.