The European Space Agency (ESA) this week announced the first two missions selected for its Cosmic Vision 2015-2025 Plan. The first, known as Solar Orbiter, will see a spacecraft operating closer to the Sun than any previous mission with a particular focus on examining the solar wind. The second, Euclid, is essentially a space telescope whose primary goal is to study the accelerating expansion of the universe in an attempt to provide an understanding of the exact nature of dark matter.

Solar Orbiter

With the aim of improving our understanding of the ways in which the Sun influences its environment, the Solar Observer will examine how the Sun generates and propels the flow of charged particles that form the solar wind in which the planets are bathed and which can wreak havoc on power grids on Earth and satellites in orbit.

The spacecraft is designed to operate 42 million kilometers (26 million miles) from the Sun, closer than any previous mission and close enough to sample the solar wind shortly after it has been ejected from the solar surface. Its proximity will also enable it to observe in great detail the process accelerating the wind on the Sun's surface that allows the particles to escape the Sun's gravity.

The Solar Orbiter's launch is planned for 2017 from Cape Canaveral using an Atlas launch vehicle provided by NASA.


Named after the Greek mathematician often referred to as the "Father of Geometry," the Euclid mission will attempt to map out the large-scale structure of the Universe with unprecedented accuracy and attempt to understand the exact nature of dark energy. In an effort to explain why the Universe is expanding at an ever-accelerating rate, Euclid will observe several hundreds of millions of galaxies over a large fraction of the sky to track the observational signatures of dark energy, dark matter and gravity. The observations will stretch across 10 billion light years into the Universe, revealing the history of its expansion and the growth of structure during the last three-quarters of its history.

With current observations suggesting that dark energy comprises more than 70 percent of the matter-energy density of the present-day universe, astronomers say that measuring the apparent shapes and the distribution of galaxies in the Universe will constrain the nature of dark energy and allow them to examine whether the general theory of relativity is still a valid description of gravitation on scales of billions of light years.

Euclid's launch is planned for 2019 from Europe's Spaceport at Kourou, French Guiana, on a Soyuz launch vehicle.

"With the selection of Solar Orbiter and Euclid, the Science Programme has once more shown its relevance to pure science and to the concerns of citizens: Euclid will shed light on the nature of one of the most fundamental forces of the Universe, while Solar Orbiter will help scientists to understand processes, such as coronal mass ejections, that affect Earth's citizens by disrupting, for example, radio communication and power transmission," says Alvaro Giménez, ESA's Director of Science and Robotic Exploration.

The ESA's Cosmic Vision 2015-25 Plan was created in 2005 after consultation with the wider astronomical community and identified four scientific aims: What are the conditions for life and planetary formation? How does the Solar System work? What are the fundamental laws of the Universe? How did the Universe begin and what is it made of?

The ESA issued a "call for missions" around these aims in 2007 and three medium-class missions were subsequently considered, of which the Solar Orbiter and Euclid missions are the first to be selected. A third mission, called PLATO (PLAnetary Transits and Oscillations of stars), proposed using a number of small, optically fast, wide-field telescopes to detect and characterize a large number of close-by exoplanetary systems. Although it didn't make the cut this time, the Science Programme Committee decided to maintain the mission as a possible competitor for a future flight opportunity.

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