The IGY began on July 1, 1957 and was planned to be a series of measurements taken at points all over the world during a period of maximum sunspot activity. Slough played a major part in this enterprise, housing one of four World Data Centres for the collection and exchange of ionospheric information. The success of the IGY led to the programme being extended to the end of 1959. The world-wide collaboration in upper atmospheric measurements, through the World Data Centre system continues to this day. Further collaborative years have since been organised, such as the International Quiet Sun Year (1964-65) and the Active Sun Year (1968-69).