Thermal performance prediction of the TMT optics

Abstract

Thermal analysis for the Thirty Meter Telescope (TMT) optics (the primary mirror segment, the secondary mirror, and the tertiary mirror) was performed using finite element analysis in ANSYS and I-DEAS. In the thermal analysis, each of the optical assemblies (mirror, mirror supports, cell) was modeled for various thermal conditions including air convections, conductions, heat flux loadings, and radiations. The thermal time constant of each mirror was estimated and the temperature distributions of the mirror assemblies were calculated under the various thermal loading conditions. The thermo-elastic analysis was made to obtain the thermal deformation based on the resulting temperature distributions. The optical performance of the TMT optics was evaluated from the thermally induced mirror deformations. The goal of this thermal analysis is to establish thermal models by the FEA programs to simulate for an adequate thermal environment. These thermal models can be utilized for estimating the thermal responses of the TMT optics. In order to demonstrate the thermal responses, various sample time-dependent thermal loadings were modeled to synthesize the operational environment. Thermal responses of the optics were discussed and the optical consequences were evaluated.

Advances in aerothermal modeling for TMT

“…Therefore the additional heat flux on the mirror surface caused by the actuator plumes is modeled in this simulation. The actuator surfaces will be ~0.7K above ambient temperature [7]. Figure 3 shows the resulting heat flux with the above boundary condition.…”

“…Since the solid thermal model described in [7] models also the edge sensor preamplifiers the resulting heat flux from those sources need not be modeled. However, the solid thermal model requires the convective heat transfer coefficient as input.…”

“…A two-year environmental record measured on the TMT baseline site [6] provides ambient condition variability. The Segment Support Assembly (SSA) CFD model provides heat transfer coefficients to the SSA solid thermal model [7], which in turn provides heat fluxes to the mirror thermal model. The surface thermal model provides heat fluxes to the TMT observatory CFD model.…”

Statistical approach to systems engineering for the Thirty Meter Telescope

“…They include CFD simulations of the observatory on the TMT site [12], the radiation-convection enclosure skin temperature model, and the solid thermal models of the optical elements [14], their support structure and the telescope structure [15].…”

Thermal modeling environment for TMT

“…A 3-year environmental record [3] measured on 13N, Mauna Kea, the TMT site, provides ambient condition variability and the corresponding telescope pointing record from Gemini orth provides orientation statistics. The CFD models provide heat transfer coefficients to the Segment Support Assembly (SSA), M21M3 and telescope structure FE solid thermal models [4,5], which in turn provide temperature and heat fluxes to the CFD models as boundary conditions for the telescope and optical surfaces. The surface thermal model provides heat fluxes to the CFD models for the enclosure surfaces.…”