TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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Chapter 4 enclosures, and stable laser metrology systems will all be key activities leading to the development of this testbed. Hexapod/Test Article Vacuum/Low Turbulence Stable Thermal Environment 3 Laser Ranging Interferometers Each Measuring 1 Angle and 1 Displacement Additional lasers or splitters may be required to monitor base Stable Optical Bench Second-stage vibe isolation First-stage vibe isolation Ground Figure 4-2. Schematic of the Precision Hexapod Tesbed. 58
Structural, Thermal, and Spacecraft Technology 4.1.3 Precision Structural Stability Characterization Objective The TPF Coronagraph will have to rely on extreme structural and thermal stability to achieve its performance goals. The objective of this work is to determine, with the high degree of precision necessary, the material and sub-component characteristics necessary for accurate modeling of the thermal and dynamic stability of the TPF-C telescope performance. Most importantly, the thermo-mechanical linear and non-linear characteristics and their scatter need to be tested and identified to levels consistent with the error budget. At present, the error budget for the TPF-C concept at 4λ/D with an 8-m PM requires that the rigid-body position of the PM relative to the SM be better than 25 nm over the 10-m separation, and that the RMS PM surface figure over the first 15 Zernicke modes be better than about 300 pm during the course of an observation, which entails a 36 degree dither and approximately 2 hours of data collection at station. This activity will assure that material properties and models of critical sub-components are characterized to levels of precision commensurate with the mission requirements, which in many cases is at or beyond the current state-of-the-art. Approach This activity will develop several experimental test facilities contributing to improved knowledge of precision stable structures, as described below. Note that since the facilities described herein are for the purpose of material characterization and model validation only they are not associated with any TRLs. Precision Dilatometer Facility We take advantage of the (Cryogenic) Precision Dilatometer Facility (PDF) developed at JPL for JWST to characterize the thermal strains, material variability, and long term dimensional stability of relevant precision optical materials, at any temperature between 305 K and 20 K. The facility is shown in Figure 4-3, along with an example of measured data in Figure 4-4. This facility is now being calibrated, and recent data shows that the error in the instantaneous coefficient of thermal expansion is approximately 2 ppb/°C, at least an order of magnitude better than other existing test facilities in the United States typically used for this kind of measurement. Preliminary sensitivity analyses on mirror CTE variations for the TPF-C Minimum Mission configuration have shown figure requirements were achieved with variations of 5 to 15 ppb/°C, representative of ULE fabrication capabilities. This implies that the PDF has sufficient precision to characterize material CTE to tolerances required for TPF-C analyses. Examples of materials to be tested include ULE and Zerodur for optical mirrors, PMN for the deformable mirrors, and titanium and various metals for mechanical components or flexures. Other mechanical and thermal properties will also be gathered from the literature or tested when necessary. It will be important to also capture the accuracy with which this data has been measured, so as to propagate the measurement uncertainties within the analytical predictions. This implies that all 59
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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
Page 20 and 21: Chapter 1 Surrounding the whole tel
Page 22 and 23: Chapter 1 Pol. BS fold/steering Mic
Page 24 and 25: Chapter 1 1.6.5 Sunshield The teles
Page 26 and 27: Chapter 1 expected architecture dow
Page 28 and 29: Chapter 1 Table 1-3. TPF-C Technolo
Page 30 and 31: Chapter 1 3B: Demonstrate, using th
Page 32 and 33: Chapter 2 2 Error Budgets 2.1 Contr
Page 34 and 35: Chapter 2 Error Budget Validation G
Page 36 and 37: Chapter 2 Further, it is shown that
Page 38 and 39: Chapter 2 Table 2-1. Requirement on
Page 40 and 41: 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 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 92 and 93: Chapter 4 surface polish is nonethe
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
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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
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Chapter 7 7.3 Error Budgets 7.3.1 D
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Chapter 7 7.4 Optics and Starlight
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Chapter 7 7.4.2 Apodizing Masks and
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Chapter 7 7.4.4 Wavefront Sensing a
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Chapter 7 7.4.6 Transmissive Optics
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Chapter 7 7.4.8 Scatterometer Scope
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Chapter 7 7.5 Structural, Thermal,
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Chapter 7 7.5.3 Precision Structura
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Chapter 7 model of TPF-C and should
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Chapter 7 7.5.6 Secondary Mirror To
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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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