Although superficially very much like its predecessor Ariel 3, a partial change in the experiment payload produced in Ariel 4 a cheap and ‘mission oriented’ satellite - that is to say, one in which all experiments contribute to the same investigation. The group objective of the Ariel 4 experiments was to examine the relation between naturally occurring radio frequency noise in the ionosphere and the influx of high energy charged particles, measured at the same time and place. The data handling system was designed to facilitate this objective. Each experiment could however make a separate contribution to other aspects of space research. Special technical compatibility problems were overcome and attitude control was achieved using the reaction between a current carrying coil and the geomagnetic field.