Optimization and additive manufacturing of a three-mirror-anastigmatic telescope

The development of mechanical structures for space telescopes is mainly driven by reducing the mass and in the same step increasing the stiffness, thus to achieve a high margin of safety against failure during launch and low costs for the satellite mission. These aspects attract more and more attention for the NewSpace movement, e.g. for constellations of earth observation and communication systems. Considering the state of the art, design of mass-reduced housings is limited by conventional manufacturing processes like CNC-milling. The possibility of additive manufacturing of metallic materials opens the door for an advanced light-weighted design based on topology optimization and thereby an ideal use of the existing material, which is distributed to optimally sustain loads occurring during launch. This article deals with the development, manufacturing and test of a three-mirror-anastigmatic telescope. In more detail, different concepts for light-weighting (topology optimization and a more traditional shell concept) will be presented. After the additive manufacturing of the AlSi40-mirrors and AlSi40-housing, the parts can be further processed by the typical process chain (e.g. single-point-diamond-turning, plating with electroless nickel), as known from high-performance optics. After integration, the mechanical behaviour will be verified with dynamic tests using a shaker and the results (e.g. the eigenfrequencies) will be compared with simulations finite-element analysis and an optical characterization will be carried out.