TPF-I SWG Report - Exoplanet Exploration Program - NASA

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C HAPTER 4 Null depth 1.E+00 1.E-01 1.E-02 1.E-03 1.E-04 1.E-05 1.E-06 1.E-07 1.E-08 6 8 10 12 Wavelength (um) Figure 4-12. Calculated null depth across the band for NaCl and AgCl wedges between 6 and 13 μm. A second key component of a beam combiner design is the field-inversion system which inverts the electric field of one of each pair of incoming beams by exactly π across the waveband, allowing the beam combiner to form a null (destructive fringe) rather than a constructive fringe. Several different methods of field inversion have been proposed, and at least two have been tested in the laboratory. One method uses a periscope-like arrangement of mirrors to produce the field inversion. This has the advantage of being effective across a very wide waveband. A second method uses pieces of glass of carefully controlled thickness known as phase plates to produce the field inversion. Figure 4-12 shows the calculated null depth for a set of silver chloride (AgCl) and sodium chloride (NaCl) phase plates. Other glass combinations potentially yielding deep nulls are also known. A third key component for the beamcombiner is the ability to control the optical path and maintain the null fringe on the star. Light at a different wavelength from the nulling band is used for this purpose, for example between 2 and 4 μm. If this light follows as much of the beam train as possible, then the phase of the null fringe can be better controlled, leading to deeper more stable nulls, important for faint planet detection. In the flight design study described next, the fringe tracking light follows the science path almost exactly and is interfered on the same beamsplitters as the nulling light. 4.6.1 Co-axial Combiners for a Formation-Flying Interferometer For the formation-flying interferometer design work, a simplified nuller was used rather than the highly symmetric MMZ design. The main benefits would be that only one internal laser metrology beam would be needed for each beam of the interferometer rather than two, the attenuation or round-trip insertion loss would be less for the metrology light, and the science light would emerge on only two beams rather than four, offering a small but significant improvement in signal-to-noise ratio at the detector. There would also be associated engineering simplifications. Because of the wide spectral band to be covered by <strong>TPF</strong>-I, the nuller is actually divided into two units stacked next to one another, one operating on the wavelength range 7 to 11 μm and the other on the range 11 to 17 μm. This arrangement necessitates an additional 74
D ESIGN AND A R C H I T E C T U R E T RADE S TUDIES Figure 4-13. Schematic layout of simplified beam combiner. metrology path and possibly a second fringe tracking system. By splitting the spectrum we generate less demanding coating requirements on the beamsplitters which must, for the highest efficiency, give a near reflection/transmission ratio (R/T) across the band. Also, single spatial mode filters (which cover these spectral bands) are becoming available. The simplified nuller uses a beamsplitter/compensator plate arrangement to obtain a near match of optical path across the waveband. Residual error in the R/T ratio is taken up using one specially fabricated coating on one side of the compensator plate. Models showed that the throughput could then be matched across the spectral band on both incoming beams to better than 1%. The residual amplitude and phase errors are then well within the compensation range of the adaptive nuller. Science detector and fringe tracking The science detector operates on the two complementary outputs of the cross-combiner. Light emerging from the cross-combiner is focused through the single-mode spatial filter (the subject of a <strong>TPF</strong>-I technology development effort) and then is dispersed through a prism before being detected on the science array. Since only two beams are output from each cross-combiner, a single science detector array (nominally a silicon:arsenic [Si:As] array) can handle all four beams from the pair of cross-combiners. The nuller layout includes a fringe tracking camera, which detects the phase on each nuller and on the cross-combiner. One beam from each nuller is extracted from the rejected light output (all the 7–17 μm wavelength starlight exits the system from this output) and is dispersed onto the camera array. From the cross- 75
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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
Page 38 and 39: C HAPTER 2 Lines of constant stella
Page 40 and 41: C HAPTER 2 presence of zodiacal clo
Page 42 and 43: C HAPTER 2 S EZ 2π ∫ θ max ∫
Page 44 and 45: C HAPTER 2 Figure 2-11. Observation
Page 46 and 47: C HAPTER 2 Figure 2-12. Models of t
Page 48 and 49: C HAPTER 2 Beichman, C. A., Fridlun
Page 50 and 51: C HAPTER 2 2.7.4 Suitable Targets E
Page 52 and 53: C HAPTER 2 Reach, W. T., Franz, B.
Page 54 and 55: C HAPTER 3 3.1.1 Darwin/TPF-I Prope
Page 56 and 57: C HAPTER 3 clouds or an OB associat
Page 58 and 59: C HAPTER 3 Figure 3-3. Three possib
Page 60 and 61: C HAPTER 3 the circumstellar disk,
Page 62 and 63: C HAPTER 3 Figure 3-6. (Left panel)
Page 64 and 65: C HAPTER 3 Continuum interferometry
Page 66 and 67: 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
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Page 118 and 119: C HAPTER 5 5.3.5 Beam Transfer betw
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-
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C HAPTER 5 5.8.4 Angular Resolution
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C HAPTER 5 Table 5-3. Angular Resol
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C HAPTER 5 The optimization works b
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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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