Deep-space antenna for Rosetta mission: design and testing of the S/X band dichroic mirror

The paper presents the design, fabrication, and testing of a dichroic mirror to be operated in the deep-space antenna of the European Space Agency in Perth, Australia. The dichroic mirror is designed for combining the signals in the S and X bands in the beam-waveguide feeding system of the 35 m reflector antenna. The final design consists of a thick metal plate of 2.5 m in diameter, perforated periodically with rounded cross-shaped holes. The design of such a structure required a trade off between electrical, mechanical, and technological constraints. The design and testing of a validation sample as well as of the final mirror are discussed.