Active reconstruction and alignment strategies for the Advanced Technology Solar Telescope

摘要

The Advanced Technology Solar Telescope (ATST) is a 4m off-axis telescope with a Gregorian front end. At the time of its construction it will be the world's largest solar astronomical telescope. During scientific operations the ATST mirrors and structure will be deformed due to thermal and gravitational loading. The ATST team has developed a quasi-static alignment scheme that utilizes the wavefront sensing signals from at least one and as many as three wavefront sensors in the telescope science field of view, and active figure control of the primary mirror and rigid body control of the secondary mirror to achieve least-squares optical control of the telescope. This paper presents the quasi-static alignment model for the ATST, and three different active alignment schemes that are the damped least-squares control, force optimized control that defines a least-squares aligned state of the telescope subject to minimum primary actuator force, and pivot-point control of the secondary mirror. All three strategies achieve the desired minimum RMS wavefront error, but demonstrate different optimized states of the telescope.