TPF-I SWG Report - Exoplanet Exploration Program - NASA

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C HAPTER 5 5.3.5 Beam Transfer between Spacecraft The active pointing mirror is controlled by beam shear sensors located behind a mirror on the next spacecraft. This continuously relays signals via an RF system to maintain accurate pointing. For interspacecraft transfers, the mirrors are arranged so that there is maximum shielding of the mirror from the sunshade of the next spacecraft. This is important for stray light mitigation. In earlier <strong>TPF</strong>-I designs, the number of folds and their angles were maintained in a symmetric fashion for each beamtrain. In this design, the fold angles are allowed to vary resulting in easier engineering of the layout and the consequential small asymmetries are compensated for by the adaptive nuller. Figure 5-6. First side of vertical optical bench. Figure 5-7. Second side of vertical optical bench. 5.3.6 Stray-Light Modeling Analysis showed that for a beam transfer mirror a view of the opposite spacecraft’s sunshade, particularly the gap between the topmost shades, would admit an excessive number of stray-light photons into the science beam. This is because of the small imperfections of real mirrors and the need to detect extremely low levels of light from the target. Two stray-light analyses were performed, one a simple spreadsheet analysis and the other using an optical modeling code known as FRED (developed by Photon Engineering). Good agreement was obtained between these models for collector–collector transfers. Both models showed that for beam transfer heights 4 m above the sunshades, the collector–collector separation could be as much as 165 m. Baffle diameter was 125 mm at the transmitting spacecraft and 150 mm and the receiving spacecraft. Further analysis is needed for beam transfers between collector and combiner. 5.3.7 Combiner Spacecraft The combiner spacecraft contains the majority of the optical systems. Each beam train is replicated exactly with minor differences at the simplified nuller. The top of the spacecraft receives the beams in a “maximum shading” arrangement and folds them down onto one side of a two-sided vertical main bench, see Figure 5-6. Here the beams are compressed to 30 mm diameter and passed through multistage delay lines before passing through to the opposite side of the bench and entering the adaptive nullers as shown in Figure 5-7. At the output of the adaptive nullers the beams are sent to the switch and into the nulling 104
<strong>TPF</strong>-I F L I G H T B ASELINE D ESIGN beamcombiner. The exit pupil of the adaptive nuller forms the pupil of the beamcombiner system. The nuller bench is appended to the base of the vertical bench. 5.3.8 Beam Conditioning The beam conditioning systems are: pupil stops and apertures to define the beams and restrict stray light, DM (on the collector spacecraft), adaptive nuller to tune amplitude and phase across the spectrum, delay lines for coarse through fine stages of fringe acquisition, and pointing and shear detectors for both interspacecraft beam transfers and for internal alignment principally on the beamcombiner spacecraft. Another system needed in the FFI design allows adjustment of the polarization angle of the incoming beams which can change as the spacecraft drift. The final system is the single mode spatial filter placed before the science detector. This selects the fundamental mode of the beam and reduces the sensitivity to shear and pointing misalignments as well as higher order beam asymmetries. 5.3.9 The Adaptive Nuller The adaptive nuller consists of a deformable mirror placed at the focus of a parabolic mirror in an arrangement similar to a cat’s eye delay line. At the focus, the input beam is dispersed in wavelength and separated into two orthogonally polarized stripes. By pistoning the mirror elements, phase can be added or subtracted from different spectral regions of the beam; and by tilting the mirror elements across the length of the stripe, the pointing of the output beam can be varied. By clipping the output beam against an aperture, the beam intensity can be varied for a particular range of wavelengths. One of these systems is placed in each beam, and it allows the correction of small differences in throughput and phase between beams arising from alignment changes and variations between optical components throughout the beam train. This capability operates independently on orthogonal polarizations. 5.3.10 Delay Lines A multistage delay line is conceived for this system. A coarse stage of >20 cm range allows initial acquisition of the fringe and it is then parked. Subsequent stages allow range adjustment from 50 pm to 5 cm in three stages. The fine stage is a high speed stage based on a similar concept to stages used in JPL’s Planet Detection Testbed3. These are re-actuated piezo-electrically driven stages capable of moving a 50 mm diameter mirror a distance of 3 mm at a rate of more than 2 kHz. The fine stage is a separate item mounted on the second side of the optical bench. The other two stages form a single unit with voice coil actuation. The operating ranges of the three stages overlap the regions 50 pm to 50 nm, 50 nm to 50 μm, and 50 μm to 50 mm. 5.3.11 Alignment System Pointing and shear detectors are located at various stages in the system. A full-aperture alignment beam produced by a laser mounted on the collector spacecraft is co-aligned with the science light and used for beam shear or pointing sensing at interspacecraft transfers, after the compressors and after the adaptive nullers. The same beam is used for polarization angle sensing and correction on the beamcombiner spacecraft immediately after the compressors. Pointing adjustments are made at the last mirror before transmission to the next spacecraft, at the entrance to the compressor, and possibly at the entrance to the nullers (depending on the predicted stability). Pointing and shear corrections are made at the entrance to the adaptive nuller. 105
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JPL Publication 07-1 Terrestrial Pl
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Abstract Over the past two years, t
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Acknowledgements Twenty-two represe
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Table of Contents 1 Introduction...
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4.8.3 Post-Nulling Calibration.....
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6.4.5 Double Fourier Interferometry
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I NTRODUCTION 1 Introduction Over 2
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I NTRODUCTION et al. 2004), and res
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I NTRODUCTION Standard Interferomet
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I NTRODUCTION 1.4 References Angel,
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C HAPTER 2 0.7 to 1.5 AU scaled by
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C HAPTER 2 Table 2-2. Illustrative
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C HAPTER 2 Classical interferometry
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C HAPTER 2 trivial in the absence o
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C HAPTER 2 Figure 2-3. Simulated mi
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C HAPTER 2 would be in atmospheres
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C HAPTER 2 Figure 2-6. The mid-infr
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C HAPTER 2 Lines of constant stella
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C HAPTER 2 presence of zodiacal clo
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C HAPTER 2 S EZ 2π ∫ θ max ∫
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C HAPTER 2 Figure 2-11. Observation
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C HAPTER 2 Figure 2-12. Models of t
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C HAPTER 2 Beichman, C. A., Fridlun
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C HAPTER 2 2.7.4 Suitable Targets E
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C HAPTER 2 Reach, W. T., Franz, B.
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C HAPTER 3 3.1.1 Darwin/TPF-I Prope
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C HAPTER 3 clouds or an OB associat
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C HAPTER 3 Figure 3-3. Three possib
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C HAPTER 3 the circumstellar disk,
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C HAPTER 3 Figure 3-6. (Left panel)
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C HAPTER 3 Continuum interferometry
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C HAPTER 3 Figure 3-9: Simulated im
Page 68 and 69: C HAPTER 3 3.3 Conclusions Darwin/T
Page 70 and 71: C HAPTER 3 Nguyen, H. T., Kallivaya
Page 73 and 74: D ESIGN AND A R C H I T E C T U R E
Page 111: D ESIGN AND A R C H I T E C T U R E
Page 114 and 115: C HAPTER 5 Heavy launch vehicle. Th
Page 116 and 117: C HAPTER 5 5.3.2 Combiner Spacecraf
Page 120 and 121: C HAPTER 5 Figure 5-8. Control sche
Page 122 and 123: C HAPTER 5 Figure 5-9. First sectio
Page 124 and 125: C HAPTER 5 Figure 5-9 shows the fir
Page 126 and 127: C HAPTER 5 5.4.4 Shear Metrology Sh
Page 128 and 129: C HAPTER 5 Figure 5-15. TPF-I Fligh
Page 130 and 131: C HAPTER 5 secondary mirror along t
Page 132 and 133: C HAPTER 5 a) c) b) d) IWA = 43 mas
Page 134 and 135: C HAPTER 5 planets found. Figure 5-
Page 136 and 137: C HAPTER 5 30 25 5 M earth 3 M eart
Page 138 and 139: C HAPTER 5 5.8.4 Angular Resolution
Page 140 and 141: C HAPTER 5 Table 5-3. Angular Resol
Page 142 and 143: C HAPTER 5 The optimization works b
Page 145 and 146: T E C H N O L O G Y R OADMAP FOR TP
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T E C H N O L O G Y R OADMAP FOR TP
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T E C H N O L O G Y R OADMAP FOR TP
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F UTURE D EVELOPMENTS 7 Preparatory
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F UTURE D EVELOPMENTS • To comple
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F UTURE D EVELOPMENTS Table 7-1. Pr
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D ISCUSSION AND C ONCLUSION 8 Discu
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Appendices 167
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T E C H N O L O G Y A DVISORY C O M
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F L I G H T S YSTEM C ONFIGURATION
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F L I G H T S YSTEM C ONFIGURATION
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A PPENDIX C 2. Identical FACS fligh
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A PPENDIX C 2. Recall that the coef
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A PPENDIX C Once the formation has
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A PPENDIX C Figure C-3. Example of
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A PPENDIX C Figure C-4. FAST Flight
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A PPENDIX C The “true” time of
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A PPENDIX C References Cohen, S., a
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A PPENDIX D DC DCB DM DM DOCS DOD D
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A PPENDIX D NaCl NAR NASA NASTRAN N
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A PPENDIX E Appendix E TPF-I Review
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A PPENDIX F Alice Quillen, Universi
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A PPENDIX F Figure 3-1 - Original f
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TPF-I SWG Report - Exoplanet Exploration Program - NASA

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