SMART-1 lunar spacecraft arriving at the Moon, artwork. This spacecraft is the first part of the European Space Agency (ESA) SMART (Small Missions for Advanced Research in Technology) programme. It is the first ESA spacecraft to travel to and orbit the Moon. It is propelled by a new type of engine called an ion drive. This works by accelerating xenon ions in a magnetic field. This only provides a small amount of thrust, but it is very light and more efficient than a conventional engine. Craft powered by ion drives will be able to reach greater speeds than rocket-propelled craft, but the acceleration is slower. SMART-1 will arrive at the Moon in December 2004.