Estimation of Satellite Lifetime from Orbital Failure Experience

A method is proposed for estimating satellite lifetime from orbital failure data. The idea is to use orbital failure experience on all satellite subsystems together to estimate two average subsystem failure rates which are then used, along with the system reliability model and a priori piece part failure rates, to develop the estimate of system life. The subsystem reliability models are based on two constant failure rates, the first applying to a short period following launch during which a large portion of failures has been observed, and the second to the remainder of the system life. The development begins with the exponential reliability model, extends the results to a more general reliability model employing exponential subsystems, and then proceeds to the two failure rate model. In each case, confidence limits and probability density functions for the system mean life are presented. The method is then incorporated into a previously developed Monte-Carlo procedure for system replenishment analysis. Typical results are presented.