TPF-C Technology Plan - Exoplanet Exploration Program - NASA

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Chapter 1 Surrounding the whole telescope is a large multi-vane sunshield, whose design provides thermal stability for the facility as a whole and whose packaging allows for deployment in space. The design of TPF-C provides the necessary wavefront correction to allow high contrast imaging, as well as the control necessary to maintain wavefront control over long exposure times. The approach to starlight suppression and planet detection is described following the instrument description. 1.6.1 Telescope Design The focal length for the telescope is 146 m, and the paraxial focal ratio is f/18.2. The real focal ratios along each axis are 20.7 and 44.3 along the fast and slow axes, respectively. The axial separation between the primary and secondary mirrors is 12 m, and the distance from the secondary to the telescope focus is 15 m. The fold mirror is located 0.5 m behind the primary mirror vertex. After the fold mirror, the light passes to a second fold mirror, shown in Figure 1-5, then a collimating mirror, and then to a polarizing beamsplitter. The polarizing beamsplitter Figure 1-4. Schematic overview of the TPF-C optical layout. Table 1-2. Design parameters for the primary, secondary, and tertiary mirrors of TPF-C Mirror Radius (mm) Conic Aperture (mm) Primary 26756.027 -1.001939 8000 × 3500 2300 Secondary 3034.830 -1.470716 830 × 365 237 Fold Infinity 0.0 140 × 90 N/A 8 Off-axis decenter (mm)
Introduction separates the × and y polarizations, and hereafter the optics are duplicated for each polarization and the light in each polarization is treated separately. The following description considers one polarization only. 1.6.2 Wavefront Compensator The light now passes to a Michelson interferometer, shown in Figure 1-6. The arms of the interferometer are relatively short, and each terminates in a deformable mirror. The light is retro-reflected off the DMs, is recombined, and then sent onward to the coronagraph. This step is necessary so that the incoming wavefront can be corrected in both amplitude and phase. The two DMs provide the two degrees of freedom (DOF) necessary to correct both amplitude and phase. When the beam is recombined, it has been corrected not only for errors that exist on the telescope mirrors but also for errors due to the non-uniformity in the mirror coatings. Using a single DM, as the High Contrast Imaging Testbed (HCIT) does currently, it is possible to correct both phase and amplitude errors over a half-dark hole, or the phase errors over a full-dark hole yielding a reduced contrast. 1.6.3 Coronagraph Design This near-perfect wavefront is then relayed to a pupil plane where a mask is inserted to block starlight. The pupil-plane mask diffracts the starlight away from the field of the habitable zone. The light is then imaged at a focal plane where an occulting mask is fold inserted to block the central starlight that passes through. The next image locations step is to re-collimate the beam, Lyot which will send any diffracted light out to the edges of the field. This F/60 beam ring of light is blocked by a Lyot stop. Finally, the beam is relayed occulting mask into a focus mirror which images it onto the science camera. After the telescope is rolled, the residual background light can be subtracted and the camera will see an image similar to what is shown in Figure 1-7. The half of a squareshaped dark hole is created because of the square arrangement of the deformable mirror actuators. If the actuators were arranged in a hexagonal pattern, the dark hole would also be hexagonal. If the speckles were caused only by phase errors, the full dark hole with a bright line running through would fold/steering 2 nd fold DM pupil fold/steering Figure 1-5. Coronagraph optical layout. 9
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Page 60 and 61: Chapter 3 The wavefront quality of
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Chapter 4 enclosures, and stable la
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Chapter 4 facilities from which dat
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Chapter 4 Figure 4-5. Microslip Tri
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Chapter 4 Figure 4-7. Calibration o
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Chapter 4 Figure 4-8. Comparison of
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Chapter 4 4.2 Subsystem and System
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Chapter 4 Figure 4-11. Schematic of
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Chapter 4 Figure 4-12. Fine guiding
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Chapter 4 (5) The Fine Steering Mir
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Chapter 4 Third, precise thermal co
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Chapter 4 giving confidence that fl
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Chapter 4 surface polish is nonethe
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Chapter 5 TPF-C is planning a suite
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Chapter 5 engineering judgment (i.e
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Chapter 5 categories, in reality ea
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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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