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The Mars Surveyor '98 program recently sent two spacecraft to Mars, consisting of an Orbiter and Lander launched separately on Boeing Delta 7425 launch vehicles. The Mars '98 mission was to have added to the knowledge gained by the Mars Global Surveyor and Mars Pathfinder missions. Unfortunately, both vehicles were unable to complete their missions upon reaching Mars. This paper describes the requirements, design and operational cruise performance of the Mars Climate Orbiter (MCO) and the Mars Polar Lander (MPL) Electrical Power Systems, including detailed discussions on each of its key components. A technical risk assessment of implementing a single battery EPS design is included, along with a detailed comparison of this architecture to a block redundant EPS architecture incorporating redundant batteries. The paper concludes with a discussion of additional present and future spacecraft mission applications utilizing this EPS architecture and the associated benefits to these missions. It should be noted that the single battery Electrical Power Subsystem (EPS) approach in no way contributed to the loss of either of these spacecraft.