TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Integrated Modeling and Model Validation
5 Integrated Modeling and Model Validation
5.1 Technology Rationale
Because of the size and complexity of the TPF-C design concepts, the end-to-end system will
never be tested on the ground. The project will have to rely heavily on the use of engineering and
science simulations to predict on-orbit performance requirements from the lowest level of
assembly on up. Furthermore, current understanding of the system indicates that the 8-m class
optical system needs 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, optical diffraction and polarization effects, and all other
second order physics typically ignored. This further imposes extreme challenges on the approach
to experimental validation of models, since ground testing conditions and sensor accuracy will
often exceed performance levels expected on orbit. The TPF-C technology plan will address the
means by which models and analyses will be validated to meet the mission needs.
For full verification of the on-orbit performance, analyses will have to incorporate all the subsystem
features leading to an end-to-end simulation as depicted in Figure 5-1.
Analyses will not be limited to predicting the end-to-end TPF-C system contrast, but will be
extended to simulate the full planetary signal extraction process, incorporating planetary system
models as well as the complete on-orbit observational maneuvers for speckle removal. This
implies that new modeling tools and analysis paradigms, which emphasize computational
accuracy, and fully integrated simulations will have to be developed.
The goal of the Integrated Modeling and Model Validation Technology is to develop and
validate on testbeds a modeling methodology which authenticates the processes and models that
will eventually be implemented for predicting the TPF-C flight performances. This will involve
modeling the testbeds to the best of our ability by comparing measured and predicted
performances, quantifying Modeling Uncertainty Factors (MUFs) to reflect where the agreement
between the model predictions and measurements break down, incorporating the MUFs within
the testbed requirements to validate the error budget allocation process, then incrementally
implementing the same procedure to build up the flight system models starting with the flight
materials characterization through to model validation of progressively higher levels of flight
hardware assembly.
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