The Optical Systems of both ESA-Satellites 'Herschel' and 'Planck'

The ESA Space Observatories Herschel and Planck will be launched at April 16th, 2009 by an Ariane-5 ECA. While 'Planck' will study the cosmic microwave background radiation, the three scientific instruments of Herschel will cover the far infrared to sub-millimetre parts of the spectrum (from 60 to 670 μm), where the forming of galaxies in the early universe and their evolution can be observed. The telescopes of both satellites represent landmarks in many regards, especially the prime mirror of the Herschel telescope with 3.5 m in diameter, which is the largest mirror ever built for a space telescope. Both optical subsystems will be described in detail.