Herschel/Planck program - spacecraft design solutions for two science missions

This paper describes the technical challenges of the two science missions Herschel, an observatory-type mission, and Planck, a survey mission, are combined in one program within ESAs long-term science program. Herschel, an observatory mission, will target the largely unexplored infrared and sub-millimeter part of the electromagnetic spectrum from 60 to 670 microns with three scientific instruments. The objective for Planck, a survey mission, is to image systematically the whole sky simultaneously with two scientific instruments in nine frequency channels between 30 and 900 GHz to unravel the temperature fluctuations, the anisotropy, of the cosmic background radiation. An earlier paper discussed the design and development of the scientific payload. This paper focuses on the particular characteristics and design solutions adopted for each spacecraft to meet the challenging performance requirements demanded by the payload. For both satellites, which will be launched from the European Space Port in Kourou, French Guiana, on a single Ariane 5 launcher in the 3rd quarter of 2007, the orbits will be Lissajous orbits around the 2nd Lagrange Point L2 of the Earth-Sun system.