TPF-I SWG Report - Exoplanet Exploration Program - NASA

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C HAPTER 4 combiner, two beams are extracted, so a total of four beams are sensed at the array. For the second crosscombiner a second fringe tracker would be needed unless a laser metrology could be used to transfer measured phase to the second nuller. 4.6.2 Multi-Axial Beam Combiners In contrast to classical beamsplitter-based beam-combiner designs, it is also possible to combine optical beams using single-mode fibers. Technology at long wavelengths has not advanced to the point where each of the various beams to be combined can be injected into separate fibers and then combined using cross-couplers. However, another approach is feasible. Separate beams can be directly combined into a single fiber simply by using a common focusing optic, as in Figure 4-14. Each of the individual beams must couple to the same spatial mode in the single-mode fiber. Thus, if the beams (in the two beam case) arrive with a relative phase shift of π radians, the two beams entering the fiber mode will cancel each other. Note that a large number of beams can be combined in one step, as a number of beams around the periphery of a common focusing optic can all be simultaneously focused onto the common fiber tip (Figure 4-15; Karlsson et al. 2004; Wallner et al. 2004). This method of “fiber nulling” has now been verified in the optical regime, where deep narrowband nulls close to one part in a million have already been obtained (Haguenauer and Serabyn 2006) , and in the near-infrared, where broad-band nulls of a few 10 -4 have been obtained across the H band (Figure 4-16; Mennesson et al. 2006). However, while simple and easy to use, this nulling approach also has disadvantages, including lower efficiencies in the case of a small number of beams, and the lack of a complementary, or “bright” output. Thus, more experience with this type of combiner is required to fully understand the trade-offs relative to classical beamcombiners. Focal plane intensity Single-mode waveguide Fiber fundamental mode Single sub-pupil intensity Interference intensity beam 1 Focusing optics beam 2 Combined field amplitude Transversal cuts in focal plane Figure 4-14. Principle of single-mode fiber beam combination. The two beams are combined by the same focusing element onto the core of a single-mode fiber. 76
D ESIGN AND A R C H I T E C T U R E T RADE S TUDIES Figure 4-15. Layout for multi-beam combination. The beams (small circles) are all focused onto the core of a single-mode fiber by the same focusing optic (large circle). Figure 4-16. Measured H-band null depths. The best null in this 10-s running average is 6.5 × 10 -5 (Mennesson et al. 2006). 4.7 Stray Light The light that is collected by each telescope is relayed through free space to the central beam combiner where interference fringes are formed. The optics of the beamcombiner must restrict the field of view looking back toward each telescope in order to strongly attenuate or block sunlight that might be reflected off the outer edges of the telescope spacecraft – in particular off the rim of the sunshields. The adopted solution has been to place the relayed light paths as far above the plane of the heat shields as possible, 77
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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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Page 44 and 45: C HAPTER 2 Figure 2-11. Observation
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Page 48 and 49: C HAPTER 2 Beichman, C. A., Fridlun
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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
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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
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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
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Page 138 and 139: 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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