Introduction to the ESRO Spacecraft ESRO-II/IRIS, ESRO-I/Aurorae and HEOS-I

Abstract

ESRO-II was launched in May 1968, ESRO-I in early October 1968, and HEOS-1 in early December 1968. The solar event of February 25, 1969 was the first to be seen by all three satellites. For that reason, and not because of any particularly exciting solar features, was the event chosen for discussion. Choice of a later event would have given even less time for data analysis before the Symposium and there was no guarantee that at that later time all three satellites would still be operational. Indeed, there was no guarantee that another convenient solar event would arrive in time. The February 25, 1969 event was made more attractive by the fact that several ESRO rockets were launched from the Northern auroral zone at that time as part of a PCA campaign.