TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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Chapter 3 vacuum-compatible, low-power 64-channel multiplex switch ASIC has been developed at JPL to distribute the voltage settings while minimizing the number of control wires that must pass through the vacuum chamber wall. The products to be developed are 32 × 32, 48 × 48, 64 × 64, and 96 × 96 deformable mirrors leading toward technical hardware that are reliable, large enough, and robust enough to support flight performance levels required by Sept. 2008. Module development and combinations will enable a best understanding of last path for flight hardware development. In addition, Boston Micromachines is providing DMs for the GSFC Michaelson testbed, Princeton pupil plane testbed, and NOAO PIAA testbed with a similar architecture to the DMs required by HCIT. Boston Micromachines also provides the Visible Nuller (VN) with segmented DMs. The alternative approach and supplier represented by these MEMS DMs provide risk mitigation. Progress to Date Xinetics has delivered five 32 × 32 actuator DMs and two of four 64 × 64 actuator DMs. The 32 × 32 DMs have been used in HCIT to achieve suppression approaching 10 -9 with speckle nulling. Work is currently progressing on the 48 × 48 DM 2,304 channel single module manufacturing pathfinders, including module development, actuator machining and delineation pathfinder, interconnect evolution pathfinders, and facesheet development. Table 3-4. Deformable Mirror Specifications Deformable Mirror Property Actuators across aperture State of the Art - State of the Art - Xinetics <strong>TPF</strong>-C Flight Baseline MEMS * 32 actuators/pupil 64 actuators/pupil 96 actuators/pupil Actuator spacing 3.3 actuators/mm 1 actuator/mm ≥ 1 actuator/mm Command resolution ~5 Å surface/step † < 0.10 Å surface/step < 0.05 Å surface/step Actuator stroke ~20000 Å surface ‡ > 2000 Å surface > 2000 Å surface Actuator position stability Actuator thermal stability Mirror surface quality at uncontrollable spatial scales TBD < 0.20 Å surface/hour (includes effects of 10-mK thermal stability) TBD ~ 3.5% of stroke / K TBD ~10 nm surface § < 10 Å surface TBD < 0.02 Å surface/hour * Based on Boston MicroMachines Devices † Command resolution is currently limited by the precision of the high voltage drivers with an average step size of ~10 nm/V; with custom 16-bit electronics, an average 0.3 Å/step is expected. Current devices on order are expected to achieve up to 12-13 bit resolution or 4.9-2.4 Å/step. ‡ Nominal actuator stroke is ~20,000 Å (2 μm), however usable stroke over full aperture is limited by unpowered, surface curvature to somewhat less than this. § Small area, periodic deviations at actuator frequencies (2x outer working angle frequency) in unpolished devices. Devices on order are being polished to reduce this level. 40
Optics and Starlight Suppression <strong>Technology</strong> 3.1.5 Transmissive Optics Objective The minimum mission design incorporated two features that make use of large (greater than 10-cm clear aperture) transmissive optics. The first is a polarizer assembly consisting of a polarizing beam splitter (PBS) and two additional cubes required to achieve the required extinction while compensating for the chromatic dispersion. The polarizer assembly serves to give two separate paths for two orthogonal polarizations, each with its own set of deformable mirrors and downstream optics. The second feature is a Michelson assembly, chosen over the Mach-Zehnder due to its compactness, which accommodates wavefront control via the two DMs in each path. The total path in the glass for each sub-system is on the order of 25 cm. The objective of this effort is to identify and, if necessary, address materials issues involved in the fabrication of large transmissive optics to the required tolerances, such as the uniformity of the glass, stress birefringence, scatter and depolarization, and the chromatic variation of these. Approach The preferred approach to addressing this technology risk is to develop design options that bypass entirely or reduce the dependence on transmissive optics. Several trades are still open in the coronagraph design and may result in the elimination of the two separate polarization paths or modification of the interferometric configuration. There are two main options. The first one is to control polarization through special coatings on the mirrors along with design changes that will allow elimination of the second polarization beam path. The second one is the introduction of a non-interferometric DM arrangement, thus removing another large transmissive optic. Polarization control through mirror coating is an ongoing effort. Concepts for polarizationinsensitive occulting masks are also being considered. However, if it is decided that a configuration similar to that of the minimum design mission is needed, the technology development will be planned and initiated in Phase A. Progress to Date Progress to date has consisted solely of initial investigation into the state-of-the-art; detailed requirements have not yet been developed for transmissive optical elements. Homogeneity Published data for fused silica 15 show homogeneity values in the range of 0.5 ppm. These were assessed with blanks ~200 mm in diameter and ~50 mm thick. Wavefront error of less than ~0.007 waves rms is achievable with blank selection. Homogeneity is determined from the p-v net wavefront error upon transmission for any given blank. It therefore leaves unanswered the question of spatial distribution, which would need further study. For other optical glasses, the Schott glass catalog shows values of 1 ppm as achievable depending on the type of glass and 15 J. L. Ladison et al., “Achieving low wavefront specifications for DUV lithography; impact of residual stress in HPFS® fused silica,” Proc. SPIE 4346, 1416-1423 (2001). 41
Page 1 and 2: JPL Publication 05-8 Technology Pla
Page 3: TECHNOLOGY PLAN TERRESTRIAL PLANET
Page 6 and 7: Recent Highlights Technical progres
Page 8 and 9: Figure i-4. Deformable mirror deliv
Page 10 and 11: Table of Contents Approvals........
Page 12 and 13: 7.5.2 Precision Hexapod............
Page 14 and 15: Chapter 1 Figure 1-1. Artist's impr
Page 16 and 17: Chapter 1 interferometry, continues
Page 18 and 19: 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 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 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
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Chapter 5 5.6.1 Modeling Methodolog
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Chapter 5 strength of computer simu
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Chapter 6 6 Instrument Technology a
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Chapter 6 Figure 6-1. Detailed conc
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Chapter 6 The first method is self-
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Chapter 6 super computers and is us
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Chapter 7 7 Plan for Technology Dev
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Chapter 7 Figure 7-1. TPF-C Technol
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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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