In 2003 the Ariane 5 rocket will take into orbit a spacecraft which could dramatically increase our understanding of the universe. Just as the Rosetta stone unravelled the mysteries of Egyptian Hieroglyphics, the European Space Agency hopes that the ROSETTA mission will decode the atoms and molecules which make up a comet, and in doing so, tell us something about our own cosmic roots.
After orbiting the Earth and gathering speed, the ROSETTA will be catapulted into deep space on a ten year mission to rendezvous with comet Wirtanen. Orbiting the comet and collecting data, ROSETTA will also deploy a landing craft to remain on the comet obtaining more details.
For a mission of this duration, traditional alkaline battery technologies would present a problem. Nickel cadmium or nickel hydrogen batteries are heavy and often constitute as much as 15% of the dry mass of a typical communication satellite. Lighter batteries would either reduce launch costs or allow more useful equipment to be taken along. This consideration has been at the heart of rechargeable lithium-ion battery technology designed by AEA technology for use on the mission.
AEA’s batteries are more than 50% lighter than their alkaline equivalent. Lithium-ion cells (typically consisting of lithium-carbon negative electrodes and solid solution positive electrodes) are referred to as such because the cell can be regarded as a concentration cell in which lithium remains in the form of ions.