The PLATO (PLAnetary Transits and Oscillations of stars) mission was first proposed in 2007 as a medium-sized (M-class) candidate in response to the call for missions of the Cosmic Vision 2015-2025 programme for a launch in 2017-2018. The proposal was submitted by Dr Claude Catala (Observatoire de Paris, France) on behalf of a large consortium comprising scientists from laboratories across Europe.
Following favourable reviews by ESA's scientific advisory bodies, PLATO was selected in 2007 as one of the missions for which an ESA assessment study was carried out in 2008 and 2009. The PLATO mission was subsequently selected for a definition study, starting in February 2010.
After the non-selection of PLATO in October 2011 for the M1 or M2 launch opportunities, the ESA Science Programme Committee (SPC) endorsed the solicitation of a proposal to the PLATO Mission Consortium to be a candidate for the M3 launch opportunity in 2022–2024. The PLATO Mission Consortium responded with a proposal for the provision of the payload and science ground segment components formulated in the M3 mission framework — this was accepted by ESA. A major change was the transfer of the leading role from France to Germany, with Professor Heike Rauer (DLR, Germany) as the new PLATO Principal Investigator. The submitted science case and mission design are summarised in the Assessment Study Report (ESA/SRE(2013)5).
In February 2014, the SPC selected PLATO as the M3 mission of the Cosmic Vision 2015-2025 programme. This paved the way for the mission Definition Study which involved three concurrent industrial contracts with Airbus DS, OHB, and Thales Alenia Space. This activity covered the definition of the mission profile, the satellite, and parts of the payload module.
In addition, ESA performed the study of the PLATO science ground segment contribution and, together with e2v, of the CCDs procurement. The PLATO Mission Consortium carried out the study of the payload and of their contributions to the science ground segment.
The Definition phase concluded in May 2016 with the successful Payload, Science Ground-segment and Science Performance System Requirement Review (PSRR), and the Mission Adoption Review (MAR).
In June 2016, the SPC approved the PLATO Science Management Plan.