Reconstructor and control system tests for the new 6.5-m single-mirror MMT

Abstract

We describe the control system which will be used for the adaptive optics system to be placed on the new 6.5-meter MMT. We describe the hardware used to implement the control system, and possible algorithms to accomplish the control. A real-time reconstructor will use a linear matrix multiply to calculate the figure error using input data from a Shack-Hartmann type wave-front sensor. The mirror actuators will be controlled by a servo control-loop which uses the reconstructed wave-front and capacitive position sensors located at each actuator as feedback. The control electronics are based upon commercially available components which conform to the VME standard. We discuss the unique characteristics of the MMT design both for the reconstruction of the wavefront from the WFS measurements and the adaptive secondary servo control-loop. The control system is designed to address two unique problems associated with using an adaptive secondary mirror with voice-coil actuators. The control system must accurately control the relatively large but thin (2mm) secondary. The control system must work in the absence of a guard band around the outside of the pupil. We present timing diagrams for the flow of data through the computational units of the control electronics, and will show measured latencies for each computational component and the control system as whole.