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TMT telescope structure system - design and development - art. no. 62672Q
Abstract
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.
... The TMT telescope structure design based on the original Aplanatic Gregorian optical design was presented in the last SPIE Astronomical Instrumentation Conference in 2006 [1] . Since then, the TMT project has adopted a Ritchey-Chrétien optical design resulting in an overall height reduction of the telescope structure by 6.2 m. ...
... In addition, the quasi-static performance of the April model design under gravity was evaluated using the Merit Function Routine [1] to ensure that the lighter design also meets the active optics requirements with regard to the flexure characteristics of the telescope-mounted optics. Figure 2. Elevation structure transfer function comparison before and after mass optimization. ...
The Thirty Meter Telescope (TMT) project has revised the reference optical configuration from an Aplanatic Gregorian to a Ritchey-Chrétien design. This paper describes the revised telescope structural design and outlines the design methodology for achieving the dynamic performance requirements derived from the image jitter error budget. The usage of transfer function tools which incorporate the telescope structure system dynamic characteristics and the control system properties is described along with the optimization process for the integrated system. Progress on the structural design for seismic considerations is presented. Moreover, mechanical design progress on the mount control system hardware such as the hydrostatic bearings and drive motors, cable wraps and safety system hardware such as brakes and absorbers are also presented.
... The TMT telescope structure design based on the original Aplanatic Gregorian optical design was presented in the last SPIE Astronomical Instrumentation Conference in 2006 [1] . Since then, the TMT project has adopted a Ritchey-Chrétien optical design resulting in an overall height reduction of the telescope structure by 6.2 m. ...
... In addition, the quasi-static performance of the April model design under gravity was evaluated using the Merit Function Routine [1] to ensure that the lighter design also meets the active optics requirements with regard to the flexure characteristics of the telescope-mounted optics. Figure 2. Elevation structure transfer function comparison before and after mass optimization. ...
The Thirty Meter Telescope (TMT) project has revised the reference optical configuration from an Aplanatic Gregorian to a Ritchey-Chrétien design. This paper describes the revised telescope structural design and outlines the design methodology for achieving the dynamic performance requirements derived from the image jitter error budget. The usage of transfer function tools which incorporate the telescope structure system dynamic characteristics and the control system properties is described along with the optimization process for the integrated system. Progress on the structural design for seismic considerations is presented. Moreover, mechanical design progress on the mount control system hardware such as the hydrostatic bearings and drive motors, cable wraps and safety system hardware such as brakes and absorbers are also presented.
... The current design is shown in Figure 5-4. The DSL structural work, as well as project studies of vibration, dynamics and earthquake performance, are reported in these proceedings 23 The instrument access on the Nasmyth platforms is indicated in Figure 5-5 which shows the accessible range of the tertiary. ...
The Thirty Meter Telescope (TMT) Project will design and build a thirty-meter diameter telescope for research in astronomy at optical and infrared wavelengths. TMT is a partnership between the University of California, Caltech, and the Association of Canadian Universities for Research in Astronomy (ACURA). The $80 million TMT design and development phase is fully funded and Preliminary Design is in progress. An additional $300 million has been pledged towards early TMT construction which will commence in 2009. We include a high level description of the design of the telescope and its planned adaptive optics and science instrumentation. The schedule of key milestones for completing the design and construction is summarized.
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.