The origin of the accelerating expansion of the Universe is one of the most fascinating challenges of the 21st Century cosmology and fundamental physics. Astronomers and physicists are convinced that understanding its origin will revolutionize our concepts of quantum physics, gravity and the physics of the very early universe.

EUCLID is an ESA survey space mission designed to understand the origin of the accelerating expansion of the Universe, a quantity that physicists and astronomers refer to as "Dark Energy".

Current observations show that dark energy composes more than 70% of the matter-energy density of the present-day universe and is therefore driving its evolution.

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.

By measuring the apparent shapes and the distribution of galaxies in the Universe, astronomers will constrain the nature of dark energy and will examine whether the general theory of relativity is still a valid description of gravitation on scales of billions of light years.

To achieve this, the satellite will be equipped with a visible imager (VIS) and a near-infrared spectro-imager (NISP) developed by a European consortium comprising more than 110 laboratories and 800 scientists in Europe.

The Max Planck Institute for Extraterrestrial Physics (MPE) and the Ludwig Maximilians-University (LMU) play a major role in EUCLID. MPE is responsible for the overall optical design of the near-infrared instrument, will procure all lenses and their mounts and perform the corresponding functionality tests.

In addition, MPE is involved in the data processing of the mission. LMU is co-leading the preparation of ground-based complementary data and their merging with the EUCLID visual and infrared data.

Both institutes are represented in several science working groups, in the EUCLID Consortium Board and the ESA Science Team.

Prof. Ralf Bender, from MPE and LMU and member of the EUCLID Consortium Board, says: "EUCLID will not only provide very stringent new constraints on Dark Energy and thus may bring us a large step forward in solving physics' biggest riddle.

"It will also give many new insights into the evolution of galaxies and galaxy clusters; objects that our group has a keen interest in."

Beside ESA, the leading contributing countries forming the EUCLID Mission Consortium are Austria, Denmark, Italy, Finland, France, Germany, Netherlands, Norway, Romania, Spain, Swiss and UK, with a contribution from laboratories in the USA. German partners are the Max Planck Institute for Extraterrestrial Physics in Garching, the University Observatory Munich, the Max Planck Institute for Astronomy in Heidelberg and the University of Bonn.