Primary mirror control for large segmented telescopes: combining high performance with robustness

Future large telescopes, such as E-ELT and TMT, will need feedback control of the thousands of actuators underneath their segmented primary mirrors (M1). Differences in actuator dynamics and spatially and temporally changing disturbances make it extremely diffcult to formulate classical controllers which are both suffciently robust and highly performing. Therefore, TNO has developed and tested a control approach, in which the actual system response is quickly measured, disturbances are continuously estimated and the controller is adapted in real-Time. The algorithm is tested on an actual M1-relevant setup, in which it converges to a sub-nm optimum within a few minutes, keeps track of changing disturbances and shows its reliability over multiple days.