page_title: European Space Agency Science Programme
section_title: Medium class
hierarchical_section_title: European Space Agency Science Programme / History / Cosmic Vision / Medium class
caption_attribution_description: English: Euclid is an ESA mission to map the geometry of the dark Universe. Euclid will investigate the distance-redshift relationship and the evolution of cosmic structures. It achieves this by measuring shapes and redshifts of galaxies and clusters of galaxies out to redshifts ~2, or equivalently to a look-back time of 10 billion years. It will therefore cover the entire period over which dark energy played a significant role in accelerating the expansion. The Euclid spacecraft will have a launch mass of around 2100 kg. It will be about 4.5 metres tall and 3.1 metres in 'diameter' (with appendages stowed). The nominal mission lifetime is six years.&#160;
context_page_description: The Science Programme of the European Space Agency is a long-term programme of space science and space exploration missions. Managed by the agency's Directorate of Science, The programme funds the development, launch, and operation of missions led by European space agencies and institutions through generational campaigns. Horizon 2000, the programme's first campaign, facilitated the development of eight missions between 1985 and 1995 including four "cornerstone missions" – SOHO and Cluster II, XMM-Newton, Rosetta, and Herschel. Horizon 2000 Plus, the programme's second campaign, facilitated the development of Gaia, LISA Pathfinder, and BepiColombo between 1995 and 2005. The programme's current campaign since 2005, Cosmic Vision, has so far funded the development of ten missions including three flagship missions, JUICE, ATHENA, and LISA. The programme's upcoming fourth campaign, Voyage 2050, is currently being drafted. Collaboration with agencies and institutions outside of Europe occasionally occur in the Science Programme, including a collaboration with NASA on Cassini–Huygens and the CNSA on SMILE.
context_section_description: Medium class (M-class) projects are relatively stand-alone projects and have a price cap of approximately 500 million euros. The first two M-class missions, the Solar Orbiter heliophysics mission to make close-up observations of the Sun, and the Euclid visible to near-infrared space telescope, aimed at studying dark energy and dark matter, were selected in October 2011. PLATO, a mission to search for exoplanets and measure stellar oscillations, was selected on 19 February 2014, against EChO, LOFT, MarcoPolo-R and STE-QUEST After a preliminary culling of proposals for the fourth M-class mission in March 2015, a short list of three mission proposals selected for further study was announced on 4 June 2015. The shortlist included the THOR plasma observatory and the XIPE X-ray observatory. ARIEL, a space observatory which will observe transits of nearby exoplanets to determine their chemical composition and physical conditions, was ultimately selected on 20 March 2018. The competition for the fifth M-class mission is currently underway, with the SPICA far-infrared observatory, THESEUS gamma-ray observatory, and EnVision Venus orbiter chosen as finalists. The winning candidate will be selected in 2021.
caption: The Euclid near-infrared observatory, planned for launch as the second Cosmic Vision M-class mission.
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