On 26 February 2004, ESA issued the Mercury Planetary Orbiter (MPO) payload request for proposals. On 15 May 2004 the proposals were received and evaluated by the international Payload Review Committee (PRC), assisted by the ESTEC teams and the industrial definition study contractors.

The Science Programme Committee (SPC) in November 2004 unanimously approved the PRC recommended payload for a feasibility and definition phase of one year. In November 2005 the SPC confirmed the selected BepiColombo payload. The payload for the Mercury Magnetospheric Orbiter (MMO) is selected by the Japanese space exploration agency JAXA.