GMT integrated FEM and its role in systems engineering

The Giant Magellan Telescope Project relies heavily on integrated modeling (IM) to validate various high-level performance requirements and operating conditions of its subsystems. The deformable nature of optics and structures play a central role in these efforts, and finite-element methods are the natural choice to approximate this behavior. The integrated modeling group at GMTO maintains a detailed FE model (mesh) of the entire telescope from foundation to top-end. Representations derived from this model are a very important component of simulations studying the effects of vibrations and misalignments due to wind, gravity, temperature variations, drives, actuators, utilities, and instruments on the image formation process. This paper introduces strategies and methods specifically tailored to the unique requirements and constraints of the project, surrounding this FEM for systems engineering purposes at GMTO. This covers two closely related topics of which the second is the main focus of this paper: First, the mesh assembly, maintenance and verification processes that build upon sub-system FE modeling efforts to minimize the resources required to keep the model up-to-date with the state of the design and provide variants for trade studies. The second topic is the model abstraction process that generates static and dynamic (modal) representations of the model, primarily used in integrated time-domain simulations that also incorporate controls, optical computations and environmental inputs. The strategies and methods for this second part must take into account, among other factors, the very large size of the FE mesh, the requirements for long duration time-domain simulations with very small time steps, the very large number of inputs and outputs needed to accurately capture active and adaptive optics, the continuous evolution of designs and interfaces, verification practices, and advances in cloud computing.