The three-spacecraft AMPTE Mission was due to commence in August 1984. The purpose of these ‘active’ experiments was firstly to release lithium into the solar wind and to use the lithium ions, formed by photoionisation, as ‘test particles’ to investigate their crossing of the bow shock, their entry into the magnetosphere and subsequent energisation. Secondly, it was to release barium in the dawn magnetosheath to create an artificial comet. Thirdly, it was to inject both lithium and barium into the tail of the magnetosphere to study plasma convection. Observations were to be made both on the spacecraft and from the ground. These would provide information on the plasma physics of the natural plasma environment of the Earth and also of the formation and evolution of an expanding diamagnetic cavity. Particular attention was to be paid to the various plasma instabilities and wave phenomena anticipated in these experiments, and to the natural waves which would be observed.