Small class

Small class missions (S-class) are intended to have a cost to ESA not exceeding 50 million euros. A first call for mission proposals was issued in March 2012.^[3] Approximately 70 letters of Intent were received.^[4] In October 2012 the first S-class mission was selected.^[5] The current list of S-class missions include the following:

• S1, CHEOPS, to measure known exoplanets' size by photometry; launched on 18 December 2019.^[6]
• S2, SMILE, a joint mission between ESA and the Chinese Academy of Sciences to study the interaction between Earth's magnetosphere and the solar wind. SMILE was selected in June 2015 from thirteen competing proposals.^[7] As of June 2023, its launch is planned for May 2025.^[8][9]

Medium class

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, M1 and M2, were selected in October 2011.^[10] The M6 mission opportunity was cancelled in 2019 due to budgetary pressures.^[11]

• M1, Solar Orbiter, a heliophysics mission to make close-up observations of the Sun; launched on 10 February 2020.^[12]
• M2, Euclid, a visible to near-infrared space telescope to study dark energy and dark matter; launched on 1 July 2023.^[13][14]
• M3, PLATO, a mission to search for exoplanets and measure stellar oscillations. Selected on 19 February 2014, its launch is planned for 2026.^[15] Other competing concepts that were studied included EChO, LOFT, MarcoPolo-R, and STE-QUEST.^[16]
• M4, ARIEL (Atmospheric Remote-Sensing Infrared Exoplanet Large-survey), a space observatory which will observe transits of nearby exoplanets to determine their chemical composition and physical conditions. The mission was selected by ESA on 20 March 2018 as the fourth medium-class science mission, to be launched in 2029.^[17][18] After a preliminary culling of proposals in March 2015, a short list of three mission proposals selected for further study was announced on 4 June 2015.^[19][20][21] The shortlist included the following two proposals: THOR (Turbulence Heating ObserveR) which would address a fundamental problem in space plasma physics concerned with the heating of plasma and the subsequent dissipation of energy;^[19] and XIPE (X-ray Imaging Polarimetry Explorer) which would study X-ray emissions from high-energy sources such as supernovas, galaxy jets, black holes and neutron stars, to discover more about the behaviour of matter under extreme conditions.^[19]
• M5, EnVision, a mission to conduct high-resolution radar-mapping of select regions of the surface of Venus, as well as conduct atmospheric studies. The mission was selected in June 2021 and will launch in 2031.^[22] The call for M5 mission proposals was announced in April 2016. In May 2018, a shortlist of three candidate missions was announced, with the other two proposals being: SPICA (SPace Infrared telescope for Cosmology and Astrophysics), a far-infrared observatory; and THESEUS (Transient High-Energy Sky and Early Universe Surveyor), a space telescope to detect distant gamma-ray bursts.^[23] In October 2020, ESA announced that SPICA was no longer being considered as a candidate for the M5 mission.^[24]
• The M7 mission opportunity is currently being competed. In November 2022, five candidate missions were selected for further study: CALICO, HAYDN, M-MATISSE, Plasma Observatory, and THESEUS (M5 candidate).^[25]

Large class

Originally it was intended that Large class (L-class) projects were to be carried out in collaboration with other partners and should have an ESA cost not exceeding 900 million euros. However, in April 2011 it became clear that budget pressures in the US meant that an expected collaboration with NASA on the L1 mission would not be practical; so the down-selection was delayed and the missions re-scoped on the assumption of ESA lead with some limited international participation.^[26]

Three L-class missions have been selected:

• L1, JUICE (Jupiter Icy Moon Explorer), a mission to the Jupiter system (with heritage from Laplace); launched on 14 April 2023.^[27][28]
• L2, Athena (Advanced Telescope for High Energy Astrophysics), an X-ray observatory with a launch planned for 2035.^[29]
• L3, LISA (Laser Interferometer Space Antenna), a space mission concept designed to detect and accurately measure gravitational waves at lower frequencies than Earth-bound detectors.^[30] Its launch is planned for 2035.^[31]

Fast class

At the ESA Science Programme Committee (SPC) Workshop on 16 May 2018, the creation of a series of special opportunity Fast class (F-class) missions was proposed. These F-missions would be jointly launched alongside each M-class mission starting from M4, and would focus on "innovative implementation" in order to broaden the range of scientific topics covered by the mission. The inclusion of F-class missions into the Cosmic Vision program would require a significant increase of the science budget, to be discussed in future meetings.^[32]

Two F-class missions have been selected:

• F1, Comet Interceptor, a mission to study a long-period comet or an interstellar object (which will be determined after the launch), launching as a secondary payload together with M4, ARIEL in 2029.^[17]

• F2, ARRAKIHS (Analysis of Resolved Remnants of Accreted galaxies as a Key Instrument for Halo Surveys), a mission to survey one hundred nearby galaxies and their surroundings to investigate the development of dwarf galaxies and stellar streams; launch planned for the early 2030s.^[33]

Timeline