Microwave and millimetre wave payloads for the measurement of the Cosmic Microwave Background

The retrieval of a highly accurate map of the Cosmic Microwave Background (CMB) radiation is the scientific core of the Planck mission of the European Space Agency (ESA). The satellite will perform two complete sky surveys from its orbit around the L2 Lagrange point. The cryogenic-cooled receivers of the two instruments will measure in 10 frequency bands the microwave emission spectrum from 24 to 1000 GHz with unprecedented accuracy. The instruments are located at the focal plane of an off-axis double reflector of 1500mm projected aperture. Taken together, this assembly is an electrically large antenna varying from 120λ, to 5000λ with the operating frequencies. This paper presents the Planck microwave and millimetre wave instruments and reflectors and the expected RF performance.