On 18 October 2007, the Space Science Advisory Committee selected 6 M-class and 3 L-class candidate Cosmic Vision mission concepts for assessment studies. The M-class mission concepts are competing for 2 launch opportunities in 2017 and 2018. The first L-class launch slot is in 2020.
Candidate Missions for Cosmic Vision 2015-2025 Assessment Studies
The M-class candidate missions were Cross-Scale, Marco Polo, PLATO, SPICA, DUNE, and SPACE; the L-class candidates were XEUS, Laplace, TandEM.
These mission concepts were selected from proposals submitted by the scientific community in response to the Cosmic Vision 2015-2025 Call for Proposals issued in 2007.
LISA was already a candidate for the first L-class launch slot to compete with the candidate L-class mission concepts resulting from the Call.
Two of the original proposals, the dark universe explorer (DUNE) and the spectroscopic all-sky cosmology explorer (SPACE), had very similar science goals (i.e. unravelling the nature of dark energy) although proposed different techniques. Subsequent studies in the course of 2008 resulted in a single mission concept, Euclid, which implements both techniques.
Following discussions among ESA, NASA and JAXA, in July 2008 the XEUS mission study (originally proposed as an ESA-JAXA collaboration) and the Constellation-X study (a candidate mission in NASA) joined forces to pursue the definition of an International X-ray Observatory (IXO).
In November 2008 the Solar Orbiter study was moved into the Cosmic Vision 2015-2025 plan as a candidate M-class mission.
In February 2009 a down-selection took place between the two L-class missions Laplace (Jupiter) and TandEM (Saturn). Both missions had been proposed as collaborations with NASA, and a joint decision was taken to retain the mission to the Jupiter system as candidate for the L1 launch slot in 2020.
In February 2010 the Science Programme Committee (SPC) approved three missions to enter the definition phase, the next step required before the final decision is taken as to which missions are implemented. The three proposals chosen to proceed were Euclid, PLAnetary Transits and Oscillations of stars (PLATO), and Solar Orbiter.