The upcoming NASA's missions aimed at batteries that can operate at extreme temperatures, with high specific energy and energy densities. Since conventional aerospace rechargeable battery systems are inadequate to meet the demands, lithium ion rechargeable batteries were chosen for these missions. The 2003 Mars 2Exploration Rover mission plans to deploy twin rovers, with longer mission duration than the previous Sojourner rover, onto Mars, with the objectives of understanding its geology, climate conditions and possibility of life on Mars. The spacecraft contain various batteries, i.e., primary, thermal and rechargeable. Significant among these batteries is a lithium ion rechargeable battery, for the first time in a major NASA mission. The selection of lithium ion battery has been dictated by various factors, including mass and volume constraints, cycle life and its ability to operate well at subzero temperatures (down to -30degreesC), at moderate rates of charge and discharge. This; paper describes the considerations that led to the selection of the three battery systems on MER and the outlines the designs of these batteries.
