TPF-C Technology Plan - Exoplanet Exploration Program - NASA

Plan for Technology Development
7.2.3 Milestone 3A & 3B: Integrated Modeling of HCIT and TPF-C
Milestones 3A and 3B will demonstrate TPF-C’s technology readiness to achieve system-level
instrument performance at the 10 -10 level. This milestone will be met using a combination of
testbed results and models of the HCIT and TPF-C instrument.
Planned Completion Date: Q4 FY06
Milestone 3A will be achieved by demonstrating that HCIT models are consistent with
experimental data. An error budget, currently under development, will be used to guide this
activity. Each error source will be modeled, and experiments will be devised to validate the
model. Data and model predictions ultimately need to match to better than 1 × 10 -9 for a
bandwidth of 60nm. Initial activity will focus on matching monochromatic performance.
There are two end-to-end optical models of the testbed. A science-oriented model, which uses
plane-to-plane diffraction, is well developed and has been used to guide contrast experiments and
algorithm improvement. An engineering-oriented model, which provides full raytracing
capability in addition to diffraction, is also under development. In addition to verifying the
results of the science-based model, the engineering tool enables sensitivity calculations (which
can be compared to experimental measurements) and will be linked to structural and thermal
models of the testbed in Phase A. Both models will be enhanced with better calibration of
testbed components and incorporation of new features. The surface figures of the optics were
quickly measured prior to their installation in the testbed; more careful characterization of the
optics and their as-built alignments will be conducted. Mask characterization activities and better
DM calibration will also feed into the testbed models. The science-oriented model already
incorporates the algorithms that are used to control the testbed; these will soon also be added to
the engineering-oriented model. A polarization model will be created using different tools in the
near term, but eventually that capability should be added to the diffraction models. The results of
a stray-light analysis, conducted by a specialist, will be incorporated into the error budget and
experimentally validated where feasible.
Planned Completion Date: Q1 FY07
Milestone 3B will demonstrate, using the modeling approach validated against HCIT
performance combined with appropriate telescope models and the current mission error budget,
that TPF-C could achieve a baseline contrast of 1 × 10 -10 at discrete wavelengths and over the
required optical bandwidth necessary for detecting Earth-like planets, characterizing their
properties and assessing habitability.
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