TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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Chapter 4 surface polish is nonetheless required to minimize fixed pattern noise. This test cannot measure thermally induced wavefront changes on the order of λ/10,000, (the magnitude of change that is relevant to successful coronagraph operation). If the spherical mirror is manufactured to λ/100 rms at MSF, then it is possible that thermally induced changes on the order of λ/1000 can be tracked. Thus, this test is a thermal “overdrive test,” and the results can be correlated with the thermal system model. Likewise, simulated wheel noise excitation of the testbed can only be an overdrive test. An alternative approach is to employ the TDM in a separate test that addresses mirror stability in a room-temperature vacuum chamber. The test (like the baseline approach) requires highprecision thermal control of the mirror and the ability to apply localized, measurable temperature gradients on it. The wavefront measurement interferometer/camera is placed at the center of curvature, and its position is monitored with laser metrology, as with the baseline. The advantage of this approach is that it separates the mirror stability test from the complications presented by the cold thermal-vac chamber and hardware in the Sunshield/Isothermal enclosure testbed. Testing would entail heating the mirror in a known, measurable way while monitoring the shape of the optic. Depending on camera-to-mirror metrology precision, focus may not be measurable, but other low-order aberrations (e.g., astigmatism, coma) can be measured and compared to model predictions. The test yields the sensitivity of the mirror to thermal deformations and validates our modeling approach. However, the advantages are somewhat offset by the long radius of curvature of TDM: 7.2 m. This means that the vacuum facility is an 8–9-m-long vertical vacuum chamber. This test also does not allow the mirror to see a cold background nor is it as highly integrated as the baseline test in the cold chamber. Progress to Date To date, work has resulted only in the definition of the measurement goals and the conceptual design of the testbed. See the Sub-scale EM Sunshield and Isothermal Enclosure discussion in Section 4.2.4 for information on the development of that portion of the testbed. 80
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. 81
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JPL Publication 05-8 Technology Pla
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TECHNOLOGY PLAN TERRESTRIAL PLANET
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Recent Highlights Technical progres
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Figure i-4. Deformable mirror deliv
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Table of Contents Approvals........
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7.5.2 Precision Hexapod............
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Chapter 1 Figure 1-1. Artist's impr
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Chapter 1 interferometry, continues
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Chapter 1 Back end coronagraph opti
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Chapter 1 Surrounding the whole tel
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Chapter 1 Pol. BS fold/steering Mic
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Chapter 1 1.6.5 Sunshield The teles
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Chapter 1 expected architecture dow
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Chapter 1 Table 1-3. TPF-C Technolo
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Chapter 1 3B: Demonstrate, using th
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Chapter 2 2 Error Budgets 2.1 Contr
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Chapter 2 Error Budget Validation G
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Chapter 2 Further, it is shown that
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Chapter 2 Table 2-1. Requirement on
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Chapter 3 3 Optics and Starlight Su
Page 42 and 43: Chapter 3 are in progress with cont
Page 44 and 45: Chapter 3 Figure 3-5. Coronagraph s
Page 46 and 47: Chapter 3 (though not light-weight
Page 48 and 49: Chapter 3 Table 3-3. ITT Metrology
Page 50 and 51: Chapter 3 observations. The time it
Page 52 and 53: Chapter 3 vacuum-compatible, low-po
Page 54 and 55: Chapter 3 blank size. Westerhoff et
Page 56 and 57: Chapter 3 configurations, performan
Page 58 and 59: Chapter 3 Figure 3-10: Plots showin
Page 60 and 61: Chapter 3 The wavefront quality of
Page 62 and 63: Chapter 3 Figure 3-13. Optical layo
Page 64 and 65: Chapter 3 algorithms have limitatio
Page 66 and 67: Chapter 3 simulated star source is
Page 68 and 69: Chapter 4 Figure 4-1. Overview of t
Page 70 and 71: Chapter 4 enclosures, and stable la
Page 72 and 73: Chapter 4 facilities from which dat
Page 74 and 75: Chapter 4 Figure 4-5. Microslip Tri
Page 76 and 77: Chapter 4 Figure 4-7. Calibration o
Page 78 and 79: Chapter 4 Figure 4-8. Comparison of
Page 80 and 81: Chapter 4 4.2 Subsystem and System
Page 82 and 83: Chapter 4 Figure 4-11. Schematic of
Page 84 and 85: Chapter 4 Figure 4-12. Fine guiding
Page 86 and 87: Chapter 4 (5) The Fine Steering Mir
Page 88 and 89: Chapter 4 Third, precise thermal co
Page 90 and 91: Chapter 4 giving confidence that fl
Page 94 and 95: Chapter 5 TPF-C is planning a suite
Page 96 and 97: Chapter 5 engineering judgment (i.e
Page 98 and 99: Chapter 5 categories, in reality ea
Page 100 and 101: Chapter 5 Table 5-3. Validation of
Page 102 and 103: Chapter 5 5.6.1 Modeling Methodolog
Page 104 and 105: Chapter 5 strength of computer simu
Page 106 and 107: Chapter 6 6 Instrument Technology a
Page 108 and 109: Chapter 6 Figure 6-1. Detailed conc
Page 110 and 111: Chapter 6 The first method is self-
Page 112 and 113: Chapter 6 super computers and is us
Page 114 and 115: Chapter 7 7 Plan for Technology Dev
Page 116 and 117: Chapter 7 Figure 7-1. TPF-C Technol
Page 118 and 119: Chapter 7 Improvements to the DM ov
Page 120 and 121: Chapter 7 7.3 Error Budgets 7.3.1 D
Page 122 and 123: Chapter 7 7.4 Optics and Starlight
Page 124 and 125: Chapter 7 7.4.2 Apodizing Masks and
Page 126 and 127: Chapter 7 7.4.4 Wavefront Sensing a
Page 128 and 129: Chapter 7 7.4.6 Transmissive Optics
Page 130 and 131: Chapter 7 7.4.8 Scatterometer Scope
Page 132 and 133: Chapter 7 7.5 Structural, Thermal,
Page 134 and 135: Chapter 7 7.5.3 Precision Structura
Page 136 and 137: Chapter 7 model of TPF-C and should
Page 138 and 139: Chapter 7 7.5.6 Secondary Mirror To
Page 140 and 141: Chapter 7 7.5.8 Sub-scale EM Sunshi
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Chapter 7 7.6 Integrated Modeling a
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Chapter 7 7.7.3 Advanced Concepts:
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Chapter 8 134
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Appendices Appendix B: TPF-C Detail
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Appendices Appendix D: TPF-C Techno
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Appendices Appendix F: Acronym List
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Appendices RWA SAO SBIR SIM SM SMFA
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TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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