A programme of major science missions initiated in 1984 by the European Space Agency. Each mission is designated ‘Cornerstone’ and the programme's launches include Giotto (1985), Ulysses (1990), the Solar and Heliospheric Observatory (1995), XMM-Newton (1999), Rosetta (2004), and Gaia (2013). A Horizon 2000 Plus programme was formulated in 1994 to continue the Cornerstone missions until 2016, and other proposals include BepiColombo (2018).