Integral is ESA’s International Gamma Ray Astrophysics Laboratory, the largest ESA science satellite, providing detailed spectroscopy and imaging of celestial gamma ray sources. Integral is the first space observatory to simultaneously observe objects in gamma rays, X-rays, and visible light. It was launched in October 2002 and has been tracking violent events for over 20 years, achieving many scientific firsts. Mission end is planned for 2029.

The International Sun-Earth Explorers (ISEE) programme consisted of three spacecraft: a mother/daughter pair (ISEE-1 and ISEE-2) and the ISEE-3 spacecraft (later renamed International Cometary Explorer). The programme was a cooperative mission between NASA and ESRO (later ESA) designed to study the interaction between the Earth's magnetic field and the solar wind. ISEE-1 (Explorer 56) and ISEE-3 were built by NASA, while ISEE-2 (ISEE-B) was built by ESA. It was launched in tandem with NASA’s ISEE-1 on 22 October 1977 and its mission ended with reentry in 1987.

The Infrared Space Observatory (ISO) was the world’s first spaceborne observatory working in the infrared and made important discoveries about interstellar dust and the nature of the universe, finding clear links between stars, comets and Earth’s origins. It was launched on 17 November 1995 on an Ariane-4 from Kourou and began routine science operation in February 1996. Its mission ended with its deactivation in May 1998.

The International Space Station (ISS) programme evolved from the Space Station Freedom, a 1984 American proposal to construct a permanently crewed Earth-orbiting station, which was cancelled in 1992 over technical problems and costs. In 1993, NASA and Roscosmos negotiated an agreement to merge their space station plans into the renamed the International Space Station, with planned modules from ESA and the Japanese space programme. Station construction began with the launch of Russia’s Zarya from Baikonur in November 1998.

The International Ultraviolet Observatory, the first astronomical satellite based at geostationary altitude and an ESA-NASA-UK trilateral project. Launched in 1978, IUE was, at its time, the longest spaceborne astronomy mission with over 18 years of operations until mission end in 1996. During its life, over 1000 European observing programmes were conducted from ESA’s ‘IUE Observatory’ at the Vilafranca satellite tracking station, returning more than 30 000 spectra from about 9000 targets.