Herschel/Planck Program-Preparing for Launch and Lessons Learned

Within the long-term science program of the European Space Agency (ESA), two astrophysics missions are combined into one program: Herschel, an observatory mission and Planck, a survey mission. This paper describes the two missions; from the scientific objectives and mission design via payload and spacecraft development, to the verification and preparation for launch. It is complemented by the lessons learned in the course of the program. Herschel will target the largely unexplored infrared and sub-millimeter part of the electromagnetic spectrum from 60 to 670 microns with three scientific instruments, to study the formation and dynamics of a variety of cosmic targets. Planck will systematically image the whole sky with two scientific instruments simultaneously in nine frequency channels between 30 and 900 GHz to unravel the temperature fluctuations of the cosmic background radiation. Both satellites will be launched from the European Space Port in Kourou (French Guiana) on a single Ariane 5 launcher in 2008 to their orbits around the 2^nd Lagrange Point L2 of the Earth-Sun system.