The European Space Agency's Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity ( ΔT T ∼ 2 × 10 −6 ) and angular resolution (∼5 arcmin). Planck will provide a major source of information relevant to many fundamental cosmological problems and will test current theories of the early evolution of the Universe and the origin of structure. It will also address a wide range of areas of astrophysical research related to the Milky Way as well as external galaxies and clusters of galaxies. The ability of Planck to measure polarization across a wide frequency range (30−350 GHz), with high precision and accuracy, and over the whole sky, will provide unique insight, not only into specific cosmological questions, but also into the properties of the interstellar medium. This paper is part of a series which describes the technical capabilities of the Planck scientific payload. It is based on the knowledge gathered during the on-ground calibration campaigns of the major subsystems, principally its telescope and its two scientific instruments, and of tests at fully integrated satellite level. It represents the best estimate before launch of the technical performance that the satellite and its payload will achieve in flight. In this paper, we summarise the main elements of the payload performance, which is described in detail in the accompanying papers. In addition, we describe the satellite performance elements which are most relevant for science, and provide an overview of the plans for scientific operations and data analysis.

The properties of the hydrated electron are studied by quantum-classical molecular-dynamics simulation in a wide range of temperature and pressure, from ambient to supercritical conditions. The calculations are based on a newly developed electron-water pseudo-potential based on rigorous quantum-mechanical calculations in the static exchange limit, as well as a novel methodological approach in which the electron wave function is expanded in a basis set of spherical Gaussians, distributed on a regular cubic lattice. Although the agreement with experiment is not completely quantitative, the strong experimental red shift of the absorption spectrum found experimentally with increasing temperature is recovered and a microscopic interpretation is proposed. It is also demonstrated that the observed shift is a density rather than a temperature effect. Finally, a striking, nonmonotonic evolution of the band width with increasing temperature, or decreasing density, is pointed out.