Compact and stable earth deck multi-beam Ka-Band antenna structure and dual gridded reflector

In November 2010 the thermo-mechanical test campaign of a Ka-Band multi beam dual reflector antenna structure has been successfully finished. The innovation of this structure lies in the full CFRP sandwich design (including honeycomb core), the use of ultra high modulus fibres for all reflectors, tower panels, base panel, curved cleats, etc.) and in the bonded intersections (e.g. between base panel and tower structure), thus, reducing the in orbit thermo-elastic distortion to a minimum. In addition, the extremely low mass to high stiffness ratio is unique for European antenna structures. The interfaces to the spacecraft are titanium isostatic mounts compensating a possible CTE mismatch with the spacecraft top deck. The paper presents not only the design and the results of the dynamic test campaign, but also the innovative highly accurate thermo-elastic measurements performed under vacuum conditions using an ESPI measurement system and FBG optical sensors. Parent to the full CFRP antenna structure technology is the development of a new concept of Ku/Ka-Band dual gridded reflector (DGR): the front grid consists for e.g. a 1.2 m reflector of approx. 700 CFRP rods. The rear reflector can either be made of a solid full CFRP reflector shell or out of a second grid, which would lead to a revolutionary low DGR weight. The paper summarizes the results of the developments performed so far, up to the goal of first concepts for shaping the reflector grids, which would enhance significantly the application possibilities.