The efficient simulation of multidisciplinary thermo-opto-mechanical effects in precision deployable systems has for
years been limited by numerical toolsets that do not necessarily share the same finite element basis, level of mesh
discretization, data formats, or compute platforms. Cielo, a general purpose integrated modeling tool funded by the Jet
Propulsion Laboratory and the Exoplanet Exploration Program, addresses shortcomings in the current state of the art via
features that enable the use of a single, common model for thermal, structural and optical aberration analysis, producing
results of greater accuracy, without the need for results interpolation or mapping. This paper will highlight some of
these advances, and will demonstrate them within the context of detailed external occulter analyses, focusing on in-plane
deformations of the petal edges for both steady-state and transient conditions, with subsequent optical performance
metrics including intensity distributions at the pupil and image plane.
The next generation of space telescopes will be designed to meet increasingly challenging science goals. The operating
environment and required precision of these telescopes will make complete verification via ground tests impossible, and
will place a greater reliance on numerical simulation. The current state of the art in thermal, mechanical and optical
modeling involves three disparate computational models, several analysis codes and tools to transition results between
these models. However, the active controls necessary to meet the next generation of requirements for space telescopes
will require integrated thermal, structural, optical and controls analysis. To meet these challenges, JPL has developed
Cielo, an in-house finite element tool capable of multi-physics simulations using a common finite element model, for
thermal, structural and optical aberration analysis. In this paper, we will discuss the use of Cielo for analysis of a
coronagraph and an occulter designed to observe Earth-like planets around nearby stars. We will compare thermal and
structural results from Cielo with results from commercial off the shelf (COTS) tools to verify the new approach. We
will perform variations of key parameters to demonstrate how margins and uncertainties can be quantified using the new
Due to their scale, operating environment, and required levels of operating precision, the design of the next generation of
space-based observatories will necessarily place an ever-greater reliance on numerical simulation. Since it will be
impossible to fully ground-test such systems prior to flight, system-level confidence must come, in large part, from
correlated subsystem tests, system-level simulation, and an overall design understanding based on quantification of
margins of uncertainty, sensitivity analyses, parameter variation studies, and design optimization. Further challenges
will necessarily arise due to the actively-controlled nature of such systems, requiring fundamentally-integrated thermal,
structural, optical, and controls models. In this paper we will discuss Cielo, JPL's multidisciplinary, high-capability
compute platform for systems analysis, and describe some of the challenges in demonstrating these capabilities for the
first time on a complex model, the Space Interferometry Mission's Thermal-Structural-Optical (SIM-TOM3) testbed.
The successes and lessons learned from these activities have the potential to greatly influence subsequent test programs,
leading to greater design understanding, improved mission confidence, and significant cost and schedule reductions.
The Terrestrial Planet Finder Interferometer (TPF-I) mission requires a set of formation-flying collector telescopes that direct the incoming light to a beam combiner where the beams are combined and detected to identify habitable planets. A baseline TPF collector design, using a primary mirror of 4.2 meters in diameter, is used here to conduct a dynamic study. The objective is to investigate the effects of dynamic response of the spacecraft on the system optical performance at the presence of disturbances that arise from the reaction wheel assembly and thruster loading, respectively. Frequency responses where the frequency is associated with the flywheel speed are presented in the paper. The results focus on the surface oscillation of the primary mirror and the point at which the secondary mirror is located. Transient response simulations under the baseline four thruster-assembly configuration were conducted using various duty cycles and thrust levels determined by the TPF formation rotation requirements. This paper will also describe an investigation conducted using new IMOS (Integrated Modeling of Optical Systems), which is an open, multi-disciplinary, and Matlab-based dynamic/optical system simulation code. A pre-processor that is able to generate the sub-structure modal models required by ISYSD (Integrated System Dynamics) was developed in new IMOS. ISYSD is used to develop a high-fidelity system dynamic model by integrating the sub-structure modal models. Finally, the paper will summarize current and future work in order to meet the TPF dynamic requirements.
Accurately predicting optical performance for any of the near-term concepts proposed under NASA's Origins missions is a uniquely challenging task, and one that has served to highlight a number of areas of necessary advancement in the field of computer-aided engineering analysis. The strongly coupled nature of these classes of problems combined with unprecedented levels of required optical precision demand a solution approach that is itself fundamentally integrated if accurate, efficient analyses, capable of pointing the way towards improved designs are to be achieved. Recent development efforts have served to lay the foundation for an entirely new finite element-based analytical capability; one that is open, highly extensible, is Matlab-hosted, and which utilizes NASTRAN syntax to describe common-model multidisciplinary analyis tasks. Capabilities currently under development, a few of which will be highlighted here, will soon capture behavioural aspects of coupled nonlinear radiative heat transfer, structures, and optics problems to a level of accuracy and performance not yet achieved for these classes of problems, in an environment that will greatly facilitate future research, development, and technical oversight efforts.
Because of the complexity of the Terrestrial Planet Finder (TPF) design concepts, the project will rely heavily on the use of engineering and science simulations to predict on-orbit performance. Furthermore, current understanding of these missions indicates that the 3m to 8m class optical systems need to be as stable as picometers in wavefront and sub-milli arcsec in pointing. These extremely small requirements impose on the models a level of predictive accuracy heretofore never achieved, especially in the area of microgravity effects, material property accuracy, thermal solution convergence, and all other second order modeling effects typically ignored. New modeling tools and analysis paradigms are developed which emphasize computational accuracy and fully integrated analytical simulations. The process is demonstrated on sample problems using the TPF Coronagraph design concept. The TPF project is also planning a suite of testbeds through which various aspects of the models and simulations will be verified.