Mass budget analysis for a contactless active mirror for space telescopes

Active mirrors are considered key components for future large aperture space telescopes such as the HWO. Recently, a technology based on contactless active mirrors, developed for ground based observatory, has been proposed and preliminary tested in the lab. In a contactless active mirror, the optical surface is a thin Zerodur glass shell controlled by voice coil actuators and monitored by capacitive sensors; as a result, the optical surface is mechanically decoupled from the support. Such point has relevant implications from a system-wise perspective, as the support structure has no optical specifications any longer: in particular, the support may be extremely light-weighted, while having little to no print-through on the optical surface. The concept has been preliminary demonstrated on a 40 cm diameter prototype with 19 actuators, featuring an areal density as low as 18 kg/m2. In this work we discuss the as-build mass budget and present a roadmap to further improve the mass budget.