MIT Lincoln Laboratory’s Integrated Modeling and Analysis Software (LLIMAS) enables the development of novel engineering solutions for advanced prototype systems through unique insights into engineering performance and interdisciplinary behavior to meet challenging size, weight, power, environmental, and performance requirements. LLIMAS is a multidisciplinary design optimization tool that wraps numerical optimization algorithms around an integrated framework of structural, thermal, optical, stray light, and computational fluid dynamics analysis capabilities. LLIMAS software is highly extensible and has developed organically across a variety of technologies including laser communications, directed energy, photometric detectors, chemical sensing, laser radar, and imaging systems. The custom software architecture leverages the capabilities of existing industry standard commercial software and supports the incorporation of internally developed tools. Recent advances in LLIMAS’s Structural-Thermal-Optical Performance (STOP), aeromechanical, and aero-optical capabilities as applied to Lincoln prototypes are presented.
The Transiting Exoplanet Survey Satellite (TESS) is an instrument consisting of four, wide fieldof- view CCD cameras dedicated to the discovery of exoplanets around the brightest stars, and understanding the diversity of planets and planetary systems in our galaxy. Each camera utilizes a seven-element lens assembly with low-power and low-noise CCD electronics. Advanced multivariable optimization and numerical simulation capabilities accommodating arbitrarily complex objective functions have been added to the internally developed Lincoln Laboratory Integrated Modeling and Analysis Software (LLIMAS) and used to assess system performance. Various optical phenomena are accounted for in these analyses including full dn/dT spatial distributions in lenses and charge diffusion in the CCD electronics. These capabilities are utilized to design CCD shims for thermal vacuum chamber testing and flight, and verify comparable performance in both environments across a range of wavelengths, field points and temperature distributions. Additionally, optimizations and simulations are used for model correlation and robustness optimizations.
Advanced analytical software capabilities are being developed to advance the design of
prototypical hardware in the Engineering Division at MIT Lincoln Laboratory. The current effort
is focused on the integration of analysis tools tailored to the work flow, organizational structure,
and current technology demands. These tools are being designed to provide superior insight into
the interdisciplinary behavior of optical systems and enable rapid assessment and execution of
design trades to optimize the design of optomechanical systems. The custom software
architecture is designed to exploit and enhance the functionality of existing industry standard
commercial software, provide a framework for centralizing internally developed tools, and
deliver greater efficiency, productivity, and accuracy through standardization, automation, and
integration. Specific efforts have included the development of a feature-rich software package for
Structural-Thermal-Optical Performance (STOP) modeling, advanced Line Of Sight (LOS) jitter
simulations, and improved integration of dynamic testing and structural modeling.
Applications involving optical systems with a variety of transient loading conditions in conjunction
with tight optical error budgets require new tools to assess system performance accurately and quickly. For
example, an optical telescope in geostationary orbit (e.g.: laser communications or weather satellite) may be
required to maintain excellent optical performance with sun intermittently crossing near, or even within the
telescope's field of view. To optimize the design, the designer would wish to analyze a large number of time
steps through the orbit without sacrificing accuracy of the results. Historically, shortcuts have been taken to
make the analysis effort manageable: contributing errors are combined in a root-sum-squared fashion; non-linear
optical sensitivities to optical motions are made linear; and the surface deformation of non-circular optics
and/or footprints are fit with zernike polynomials. L-3 SSG-Tinsley presents a method that eliminates these
errors while allowing very fast processing of many cases. The method uses a software application that interfaces
with both structural and optical analysis codes, and achieves raytrace-generated results from the optical model.
This technique is shown to provide more accurate results than previous methods, as well as provide critical
insights into the performance of the system that may be exploited in the design process. Results from the
Advanced Baseline Imager ABI telescope are presented as an example.