Edgewise connectivity: an approach to improving segmented primary mirror performance

Abstract

As future astrophysics missions require space telescopes with greater sensitivity and angular res- olution, the corresponding increase in the primary mirror diameter presents numerous challenges. Since fairing restrictions limit the maximum diameter of monolithic and deployable segmented mirrors that can be launched, there is a need for on-orbit assembly methods that decouple the mirror diameter from the choice of launch vehicle. In addition, larger mirrors are more susceptible to vibrations and are typically so lightly damped that vibrations could persist for some time if uncontrolled. To address these challenges, we present a segmented mirror architecture in which the segments are connected edgewise by mechanisms analogous to damped springs. These mechanisms can be damped springs, flux-pinning mechanisms, virtual mechanisms, or any other device with the same basic behavior. Using a parametric finite-element model, we show that for low to intermediate stiffnesses, the stiffness and damping contributions from the mechanisms improve both the natu- ral frequency and disturbance response of the segmented mirror. At higher stiffnesses, the mechanisms struc- turally connect the segments, leading to a segmented mirror that performs comparably to a monolith—or better, depending on the mechanism damping—with the modular design enabling on-orbit assembly and scalability.