INO340 Active Optics System Design and Development

The Active Optics System (AOS) of the Iranian National Observatory 3.4 m telescope (INO340) is designed to support and deform the M1 and to adjust the position of the M2 with the purpose of optical aberrations' compensation. Sixty active axial pneumatic actuators and 32 passive lateral actuators support M1 axially and laterally, respectively. The arrangement and force vectors of the lateral actuators are optimized in such a way that minimum deformation on M1 occurs. There are 3 axial and 3 lateral fixed-points as positioning detectors for M1, and an accurate hexapod keeps M2 in the appropriate position. M1 surface shape and M2 positions are actively controlled by AOS during telescope operations using either a look-up table in open-loop control or the wavefront error in closed-loop control to achieve the best image quality. There are three levels of the control loop in AOS: 1- A proportional controller for a single actuator, 2- Inner-loop control to equilibrate M1 within the bandwidth of 1 [Hz], 3- Outer-loop control to remove optical aberrations within the bandwidth of 0.01 [Hz]. A test setup for the axial actuator and an Alt-simulator setup are provided to design and optimize a proportional controller for a single actuator and to test the inner-loop control. In this paper, the mechanical, control, and software designs for INO340 AOS are presented.