Galileo-probe battery-lifetime estimation

The Galileo spacecraft deployed a probe, during 1995, to investigate the atmosphere of Jupiter. It was powered by Li/SO/sub 2/ batteries that could not be tested during the 6 years of travel from Earth to Jupiter. The fundamental problem for the decision-makers during the mission was the uncertainty in knowing whether the batteries had sufficient capacity left to perform the planned mission. Battery tests performed at Ames Research Center dating back to 1984 indicated that sufficient capacity should be available. However, the statistical uncertainties associated with the data set and the inherent applicability of the data set to the in-flight set of batteries had not been considered. Accounting for all identified uncertainties, a Bayesian Weibull analysis using a Monte Carlo solution technique, determined the confidence that the battery set on-board the Galileo probe would perform adequately.