  The Dark UNiverse Explorer (DUNE) is a wide-field imaging mission concept
whose primary goal is the study of dark energy and dark matter with
unprecedented precision. To this end, DUNE is optimised for weak gravitational
lensing, and also uses complementary cosmolo gical probes, such as baryonic
oscillations, the integrated Sachs-Wolf effect, a nd cluster counts. Immediate
additional goals concern the evolution of galaxies, to be studied with
groundbreaking statistics, the detailed structure of the Milky Way and nearby
galaxies, and the demographics of Earth-mass planets. DUNE is a medium class
mission consisting of a 1.2m telescope designed to carry out an all-sky survey
in one visible and three NIR bands (1deg$^2$ field-of-view) which will form a
unique legacy for astronomy. DUNE has been selected jointly with SPACE for an
ESA Assessment phase which has led to the Euclid merged mission concept.
