Application of shape memory alloy actuators in shape correction of composite radio telescope reflector surfaces

Abstract

Composite reflector based radio telescopes are next generation instruments for radio astronomical observation which provide several benefits over traditional metal-based radio telescopes. These benefits include: improved thermal characteristics, increased surface efficiency, reduced structural weight, etc. One of the challenges in radio telescope design is maintaining the performance of the optical system throughout its operating range of elevation angles and temperature, and under the influence of wind forces. At lower frequencies, and for smaller sized dishes, this has typically meant making the structure as rigid as possible, while at higher frequencies and for larger telescopes the need for active structures is understood. Traditionally, to realize reflective surface shape correction, electric actuators such as screw jacks have been used on panelized elements which require additional support structures at a large cost in complexity and weight. Instead, shape memory alloy (SMA) wire actuators can be embedded in the composite reflectors to compensate for global and local shape changes. Maximum displacement achieved was 30 which reduced the surface RMS error by 10%. This new approach offers a very clean and simple solution (no moving parts, no support sub-structure required for actuators) which promises to be cheaper and also much lighter in weight.