The European Space Agency is about to launch its first probe to the Moon, called, SMART 1 it will test new state-of-the-art instruments and techniques essential to future interplanetary missions, such as a solar-electric primary propulsion system. It will also address key issues such as the Moon’s formation, its precise mineralogical composition, and the presence and quantity of water. The launch is due to take place on an Ariane-5 rocket on 29 August 2003, according to a press release from ESA. SMART-1 will combine the power obtained by solar-electric propulsion with lunar gravity. It will not follow a direct path to cross the 400 000 kilometres distance between the Earth and the Moon. Instead, from an elliptical orbit around the Earth where it will be placed by a rocket, SMART-1 will gradually expand the orbit in a spiral pathway that will bring it closer to the Moon every month. Finally, the Moon’s gravitational field will capture the spacecraft. SMART-1 will not land on the Moon, but will make its observations from orbit, obtaining a global view. Solar-electric primary propulsion is a new propulsion technique based on so-called `ion engines’ that feed on electricity derived from solar panels. These engines provide a very gentle thrust, but they work for years while conventional, more powerful chemical rockets burn for only a few minutes.
Ion engines need less propellant than chemical propulsion, which means less weight at launch and more mass available for scientific instruments and payload. They slash the time for interplanetary flight: although they provide less thrust they can last for years.
The gentle thrust allows very accurate spacecraft attitude control, a skill that will be useful for scientific missions that require highly precise and undisturbed pointing. SMART-1 will map the Moon’s topography, and the surface distribution of certain minerals such as pyroxenes, olivines, and feldspars. An X-ray detector will identify key chemical elements in the lunar surface. As far as communicationsis concerned, the engineers need to develop new and efficient ways to communicate with Earth from deep space, for interplanetary missions that are long or go far. SMART-1 will test both very short radio waves (called Ka band, with the instrument KaTE) and a laser experiment to try to communicate with the Earth using a laser beam, instead of traditional radio frequencies.