50 years of the European Space Agency

As Europe's organisation for space exploration marks five decades since its foundation in May 1975, Anita Chandran looks at key moments in its history

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In 2025, the European Space Agency (ESA) will reach a significant milestone: its 50th birthday. For the last five decades, ESA has brought together European countries for sustainable and collaborative space exploration, launching missions like the Cassini-Huygens probe in 1997, which ranged as far as the rings of Saturn.

ESA emerged from the need for a multinational European space programme, particularly to compete with the strength of research being produced by the USA and Soviet Union after World War Two. The organisation can trace its roots back to two separate European space agencies set up in the 1960s: the European Launch Development Organisation (ELDO), which sought to develop a launch system; and the European Space Research Organisation (ESRO), which focused on developing spacecraft. In 1975, ELDO and ESRO were merged into what is now ESA, composed then of just 10 member states.

Since its formation, ESA missions have shaped our understanding of space and advanced the technology we use for astronomy. Its first mission, Cos-B, which launched in 1975 and aimed to study gamma radiation emitted from astronomical objects, operated for four years longer than planned. Only a handful of gamma-ray sources were known before Cos-B. ESA's Integral, launched in 2002, has now taken up its mantle, investigating gamma-ray bursts by detecting not only gamma rays, but X-rays and visible light.