About 40 seconds after lift-off the rocket went off its foreseen trajectory, broke up and exploded. The four Cluster satellites that were on board, were destroyed as well. Ariane flight 501 failure. It was the first flight test of an entirely new vehicle each of whose elements had been tested on the ground in the course of the past years and months. The mission Earlier space missions to explore the Earth's magnetosphere have shown how dramatic the interaction can be between near-Earth space and the continuous stream of plasma ejected by the Sun, known as the solar wind .
Auroras are probably the most spectacular visible manifestation of plasma processes in space.
Cluster orbit configuration Cluster was going to address the structure of electromagnetic fields and the distribution of particles in the solar wind and in the Earth's magnetic field in unprecedented detail. For the first time ever, it was going to provide the means to investigate the full extent of interesting phenomena in three dimensions. A minimum of four identical spacecraft in carefully designed orbits were required to achieve this, as they must fly in scientifically meaningful configurations. The Cluster project was approved by ESA's Science Programme Committee in February 1986, within the framework of the Solar Terrestrial Science Programme, together with the SOHO project. The design and development phase started in October 1989.