TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Integrated Modeling and Model Validation
5.4 Error Budget Validation
As explained previously, the actual requirements and MUF allocations within the margin have
not been defined. As the design and project matures, the V&V matrix will be developed through
a systematic approach by identifying which terms in the error budget, starting from Level 2
requirements on down, will be validated by analysis and which will be directly validated by tests.
Each of the terms validated by analysis will be linked to a metric, such as contrast, wavefront
error, line-of-sight jitter, and so on. In turn, each of these metrics will be associated with a type
of analysis (e.g., static errors, thermal distortion analysis, and dynamic jitter analysis), each of
which requires a set of parameters and assumptions for the development of the models. In turn,
each of the models, parameters, and assumptions used for validating the error budget terms will
then need to be validated themselves through a series of tests or testbed results. During this
process, MUFs will also be allocated and verified on the testbeds.
In the current configuration, the TPF Coronagraph will operate at 4 λ/D system with an 8m
primary to achieve the top level goal of 10 -11 contrast. Work has yet to be done to flow down
these requirements to engineering performance specifications for mechanism and sub-component
stability. But based on preliminary sensitivity analyses of the Contrast metric to WFE, we know
that expected levels of stability over a 20-deg dither are as defined in Table 5-4.
Table 5-4. Required Stability Levels over a 20-Degree Dither
Description Stability Comment
Primary-Secondary Relative Motion
26 nm (z)
SM position controlled to
compensate thermal
Primary Mirror Deformation 0.4 nm 3 σ
Structural Deformation
(other than secondary)
100 nm / 10 nrad 3 σ
Rigid Body Pointing 4.0 mas 1 σ per axis
Spot Centration on Mask 0.3 mas 1 σ per axis
5.5 Model Validation
Table 5-5 is a matrix summarizing which testbeds will be used to validate the various M&MV
technologies described previously. It is shown that there exists at least one testbed to validate
each of the M&MV technologies. The model development roadmap is shown in Figure 5-2.
5.6 Progress to Date on Integrated Modeling
Technology infusion is the process of transition of the products, techniques, lessons learned, test
environments and personnel from the technology development effort to the TPF-C Flight
System. Model validation and lessons learned documentation are considered important aspects
of technology infusion and are described in the following subsections.
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