Under a Phase 1 Small Business Technology Transfer (STTR) award of $99,000 with Goddard Space Flight Center, Advanced Optical Systems Inc. (AOS) has produced a 13.5-kg/m2 6-in.-diameter mirror flat to 1 wave peak to valley (0.2 wave RMS) with no heat treatment. Many known techniques, such as heat treating, thermal cycling, and finite element analysis can further improve the mirror's merit characteristics. The surface microroughness achieved was 30-40 angstroms RMS.
AOS teamed with Oak Ridge National Laboratories (ORNL) for the STTR, taking advantage of past relationships and residual mirror technologies in place from the MODIL program. AOS and ORNL plan a Phase II follow-on to build a 0.6-meter primary and a complete telescope using the Phase I technology. The goal is areal density <6 kg/m2 in Phase II along with further improvements in material properties.
The new technology has yet to prove its merit among the beryllium and silicon-carbide mirror technologies. AOS's innovation is the casting of an aluminum-silicon alloy to near-net shapes and plating them with electroless nickel (<0.7 coefficient of thermal expansion mismatch) to produce the high-performance optical surface at low cost. The Al-Si alloy is vanasil. Material properties are low coefficient of thermal expansion, very high microyield, and low deformation.