TPF-I SWG Report - Exoplanet Exploration Program - NASA

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C HAPTER 4 Figure 4-5 shows a simplified version of the <strong>TPF</strong>-I error budget. The values shown result in an SNR of 10 for an ozone spectral channel spanning 9.5 to 10.0 μm, which currently represents the driving requirement on the integration time. The Earth-like planet orbits a G2 Sun-like star with an angular separation of 50 mas at 15 pc distance. The ecliptic latitude is 30 degrees (this determines the contribution from local zodiacal dust). The array has a linear Dual Chopped Bracewell configuration, comprising four 4-m diameter collectors spaced at 30-m intervals with phases of 0, π, π/2, and 3π/2, for a total array size of 90 m. The overall SNR is built up from 53 rotations of the array, each with a period of 50,000 s. The total observing time is 31 days (which does not currently include any overhead for calibration). The SNR for a single rotation is broken out into the root-mean-square (rms) of the planet signal variations and the contributions from random and systematic noise. The rms planet signal in this spectral band is less than 0.1 photons/s, corresponding to a fraction 2.3 x 10 -8 of the stellar signal in the same channel. In this example, the random noise has approximately equal contributions from the stellar size leakage and from local zodiacal dust. Other contributions (including exozodiacal dust emission, instrument thermal emission and stray light) have been omitted for clarity. The conversion from leakage photon rate to leakage photon noise is based on shot noise for a rotation of 50,000 s. The null floor leak term represents the photon noise arising from mismatches in the instrument beamtrains. The null floor makes a much lower contribution to the random noise budget than the local zodiacal emission and stellar leakage since it is driven by need to minimize the systematic error. The instability noise contribution to the error budget is indicated by the blue boxes, and it is chosen to be similar in magnitude to the random error. The contribution of 0.051 photon/s corresponds to a null fluctuation of order 10 -8 at frequencies similar to the planet signal. These null fluctuations result primarily from nonlinear combinations of amplitude (ΔA) and phase (Δφ) errors of the electric fields from the collectors. Analysis shows that the electric fields delivered by each collector must be matched in amplitude to within an rms error of less than 0.13% (equivalent to 0.26% intensity error), and matched in phase to within 1 milliradian at λ = 10 μm (equivalent to 1.5 nm of path). These conditions must be met simultaneously for all wavelengths in the science band, for both polarization states, and over all timescales (including direct current [DC] offsets and vibrations in the kilohertz frequency range). The null depth resulting from this level of control is 7.5 x 10 -7 . Meeting these amplitude and phase requirements is the primary technical challenge for the <strong>TPF</strong>-I system, and these requirements drive almost all aspects of the instrument design. Instability noise and its mitigation are described in more detail later in this document. In Figure 4-5 the amplitude and phase errors have been further categorized into static and dynamic terms. Static errors arise from mismatches in the coatings, the reflective and transmissive optics, and the static alignment of the system, including both dispersive and birefringent effects. Introducing an achromatic π phase shift in the nulling beam combiner has been a focus of research, but matching the transmission of the different beamtrains – each of which contains on the order of 30 optical elements – across the full range of wavelengths and polarization is also a formidable challenge. The dynamic terms include all timevariable effects. The formation-flying system is continually in motion, and a series of control systems must be used to stabilize the optical path at the 1-nm level and to manage the tilt and shear of the wavefront that couples into the single-mode spatial filter. It is clearly important to validate the static terms over an optical bandwidth that is representative of the flight system. Conversely, if the instrument can be 66
D ESIGN AND A R C H I T E C T U R E T RADE S TUDIES Integration time needed for 1 Earth mass 30.00 25.00 Dominated by Local Zodi All (1014)
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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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Page 38 and 39: C HAPTER 2 Lines of constant stella
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Page 42 and 43: C HAPTER 2 S EZ 2π ∫ θ max ∫
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
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Page 120 and 121: C HAPTER 5 Figure 5-8. Control sche
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Page 128 and 129: C HAPTER 5 Figure 5-15. TPF-I Fligh
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C HAPTER 5 secondary mirror along t
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C HAPTER 5 a) c) b) d) IWA = 43 mas
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C HAPTER 5 planets found. Figure 5-
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C HAPTER 5 30 25 5 M earth 3 M eart
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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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