Achievements and Prospects of Artificial Earth Satellites

In less than half a decade astronautics has developed from crude satellites to systems of unbelievable sophistication. Probes to Mars and Venus and a manned expedition to the moon are well into the planning and design stage. Weather and communication satellites as well as military monitoring satellites will soon be fully operational; navigation satellites are at this stage already, as are manned earth satellites. Elaborate lunar probes and complex astronomical satellites are just around the corner. However, practically all of the scientific achievements so far have been in the field of geophysics. Although some areas still remain to be investigated, many fundamental results have been gathered about the earth and its environment; briefly discussed here are findings about the figure of the earth, the density, temperature and constitution of the upper atmosphere, the nature of the radiation belt and auroral particles, and disturbances of the geomagnetic field.