The Thirty Meter Telescope (TMT) project has chosen a reference configuration with the telescope elevation axis above the primary mirror. The TMT telescope design has a segmented primary mirror, with 738 segments, nominally 1.2 m across corners, and it uses an articulated tertiary mirror to feed science light to predefined instrument positions on two large Nasmyth platforms. This paper outlines the development of the telescope structural design to meet the motion requirements related to the image quality error budget. The usage of opto-structural performance evaluation tools such as Merit Function Routine are described in addition with the optimization techniques used during the telescope structure design development.

We describe a tool to analyze the effects of gravity induced deflections on a telescope structure with segmented primary mirror optics. An objective of the telescope structural design process is to minimize image quality degradation due to uncorrectable static deflections of the optics under gravity, while ensuring that the overall system meets several requirements including limits of maximum primary mirror actuator stroke, segment rotation and decenter, and secondary mirror actuation. These design and performance criteria are not readily calculated within a finite element program. Our Merit Function routine, implemented in MATLAB and called by ANSYS, calculates these parameters and makes them available within ANSYS for evaluation and design optimization. In this analysis, ANSYS outputs key structural-model nodal displacements to a file, which are used to determine the 6 degree of freedom motion of the telescope's optical surfaces. MATLAB then utilizes these displacements, along with a database containing coordinate system transforms and a linear optics model derived from ZEMAX, to calculate various performance criteria. The values returned to ANSYS can be used to iteratively optimize performance over a set of structural design parameters. Optical parameters calculated by this routine include the optical path difference at the pupil, RMS wavefront, encircled energy and low order Zernike terms resulting from primary mirror segment rotation and decenter. Also reported are the maximum actuator strokes required to restore tip-tilt and piston of the primary mirror segments, and the deflection of the secondary mirror under gravitational load. The merit function routine is being used by the Thirty Meter Telescope (TMT) project to optimize and assess the performance of various telescope structural designs. This paper describes the mathematical basis of the calculations, their implementation and gives preliminary results of the TMT Telescope Structure Reference Design.

The Herzberg Institute of Astrophysics has developed Integrated Modeling tools for the Thirty Meter Telescope (TMT) project. This simulation software, implemented in MATLAB, models the telescope optical system, structural dynamics, and the segmented primary mirror and secondary mirror active optical control systems. For the TMT project, the integrated model was used to assess the effect of wind loading on the telescope in terms of delivered image quality. The simulation includes a state-space model of the telescope structural dynamics derived from an ANSYS finite element model, a linear optics model derived from a ZEMAX prescription, and wind loading forces derived from PowerFLOW computational dynamics software. The overall complexity of the model necessitates rigorous validation and verification procedures to ensure that the simulation data structures properly represent the original design, and that the calculations performed by the system are reliable. In this paper we discuss the validation and verification of the model data structures, structural configuration, optical configuration, coordinate system transforms, linear optics model, Zernike calculations, and wind loading model. As a case study, we present the verification, validation, and simulation results of the Thirty Meter Telescope Reference Design.