In July 1967 ESRIN and ESLAB, the two ESRO laboratories primarily concerned with basic research, held a joint symposium on Satellite and Rocket Measurements of Corpuscular Radiation from Outer Space. This was followed in September 1968 by a second symposium: Low-Frequency Waves and Irregularities in the Ionosphere; and in September 1969 by a third: Intercorrelated Satellite Observations Related to Solar Events. A fourth symposium, on upper atmospheric models and related experiments, took place in Frascati, 6-10 July 1970. The main aim of the symposium was to ssess current experimental work -...