The Bepi-Colombo mission will begin its trip to Mercury, the solar system’s innermost planet, in 2009. The spacecraft is expected to solve some long-standing puzzles about Mercury and provide insights into our own place in the solar system. The second cornerstone project is a satellite-based telescope called GAIA. Scheduled for launch before 2012, GAIA will establish the composition and evolution of the Milky Way by imaging more than a billion stars to create a three-dimensional map of our galaxy. The Laser Interferometer Space Antenna (LISA) is the third cornerstone mission and with a 2010 launch, scientists hope that LISA will detect the gravitational waves proposed by Einstein’s theory of gravity in 1915 in time for the prediction’s centenary.

With much of its technical preparation complete, the Next Generation Space Telescope (NGST) was a favourite for one of the flexible missions, and as expected, ESA has confirmed that it will contribute to the NASA-owned project. The 8-metre telescope with a broad infra-red range will shed light on many aspects of galactic and extragalactic astronomy from its orbit between the Sun and Earth. The second flexible mission is the Solar Orbiter, which will probe the Sun’s corona and heliosphere, and study the solar plasma dynamics. A reserve flexible mission has also been chosen in case problems strike – the Eddington spacecraft will study stellar evolution and search for Earth-like planets orbiting other stars.

Aided by a peer review stage, ESA chose from 49 proposals received since its call for ideas in October 1999. Among ESA’s selection criteria were scientific value, technical feasibility and a ‘science-for-money’ rating. But ‘communication potential’ was also a serious consideration: ESA insists that the scientists in charge of the chosen missions clearly explain their achievements to the European public, who, ultimately, foot the bill.