Silicon Carbide Telescope Mirrors

Abstract

The increasing demand for "exotic" telescope mirrors for space applications has prompted the examination of alternate materials and fabrication approaches. These mirrors must not only have the finely finished, precise, and stable optical surfaces generally characteristic of telescope mirrors, but they must also possess high stiffness and natural frequency and low mass or areal density. A highly efficient substrate structure is, therefore, an implicit requirement. Traditionally, mirrors have been made from glassy materials that are easily figured and polished, are thermally stable, have poor structural properties and are not amenable to fabrication into efficient structural configurations. Clearly, improved material properties and structural configurations could both reduce the mass and improve the structural characteristics of mirror substrates. A unique precision forming process developed by United Technologies Optical Systems can produce precise, complex, thin-section, monolithic formations of silicon carbide (SiC) that combine excellent material properties and highly efficient structural characteristics and offers the potential to achieve the lightweight, high performance telescope mirrors required for space. An example of this technology is shown by the inset photograph.