TPF-I SWG Report - Exoplanet Exploration Program - NASA

More documents

Recommendations

Info

C HAPTER 1 1.2 Science Objectives The major scientific objectives of TPF-I are: (1) search for and detect any Earth-like planets in the habitable zone around nearby stars; (2) carry out a study of gas giants and icy planets, as well as terrestrial planets within the 5 AU of nearby stars (at a nominal distance of 10 parsecs (pc) from the Sun) within the field-of-view of a 10-μm interferometer; (3) characterize Earth-like planets and their atmospheres, assess habitability, and search for signatures of life; (4) carry out a program of comparative planetology; and (5) enable a program of “revolutionary” general astrophysics. A mission lifetime of 5 years, possibly extended to 10 years, is foreseen. The core scientific goal of TPF-I is to detect directly and characterize Earth-like planets around nearby stars. The requirements that flow down from this goal define the characteristics of the observatory design and the mission. In particular, the ability to directly detect planets implies that TPF-I must be capable of separating the planet light from the starlight. Moreover, the facility must provide a sensitivity that will enable spectroscopic measurements of the light from the planet to determine the type of planet, its gross physical properties, and its main atmospheric constituents — the ultimate goal of course is to assess whether life or habitable conditions exist there. TPF-I will be designed so that, with a high degree of confidence, it will be capable of detecting Earth-like planets should they exist in the habitable zones of the stars in its survey. 1.3 Development of the Interferometer Architecture The overall designs for planet-finding interferometers have changed substantially since Bracewell first proposed adding a π phase shift within an astronomical interferometer to create the first nulling interferometer (Woolf and Angel 1998). This Bracewell nuller has a symmetric response on the sky, making it difficult to separate the contribution of a planet from the emission from zodiacal dust orbiting the target star (the exozodiacal emission). It is also vulnerable to small drifts in the stray light level or in the gain of the system that can mimic the planet signal. The solution was the Linear Dual Chopped Bracewell design, comprising two single Bracewell nullers that are cross-combined with a relative phase of ±π/2. By taking the difference in photon outputs of these two phase chop states, the resulting response is anti-symmetric, and is insensitive to the both the symmetric exozodiacal emission and instrumental drifts. In parallel with the introduction of phase chopping, there was development of higher-order nulling configurations. The motivation here is to reduce the impact of stellar leakage on the null depth. Although light from the center of the star can be nulled completely, light from the edges will leak through to some extent. The Bracewell designs have a null that degrades away from the optical axis as θ 2 , leading to relatively high stellar leakage. The Angel Cross combines the light from four collectors to give a null that degrades as θ 4 , reducing the stellar leakage to a negligible level (Angel and Woolf 1997; Beichman, Woolf, and Lindensmith 1999). Variations on this design include the Degenerate Angel Cross (DAC) and Generalized Angel Cross (GAC). These basic nulling elements are cross-combined using phase chopping to generate configurations such as the Chopped Degenerate Angel Cross (a linear design based on DACs) and the six-collector Bow-Tie design that was favored by ESA for a while (Fridlund et al. 2006, and references therein). 4
I NTRODUCTION Standard Interferometer 1978 Phase chop Bracewell nuller High-order null Linear Dual Chopped Bracewell Angel Cross Phase chop TPF Book, 1999 Imaging PSF Linear Dual Chopped Bracewell Chopped DAC, Laurance, Bow-tie Mission performance Minimize # spacecraft NASA Trade Study, 2004 Instability noise X-Array Diamond, Z-array, 3-Telescope Nuller Simple beam relay Stretched X-Array right-angled 3-Telescope Nuller Today Figure 1-3. Schematic showing the evolution of the preferred nulling architecture for a TPF-I/Darwin mission. These chopped high-order null configurations were thought to be superior in performance to the Linear Dual Chopped Bracewell configuration, but this proved not to be the case. Simulations to predict the number of stars that could be surveyed for planets showed that the Linear DCB could survey approximately twice the number of stars compared to a Bow-Tie with the same total collecting area. The reason is that the Linear DCB is much more efficient at converting planet photons into modulated output signal – it has a higher ‘modulation efficiency’. This is offset by the higher stellar leakage, but this only has a significant impact on the bright nearby stars that occupy only a small fraction of the total integration time available. The architecture evolution from this point has followed two parallel tracks. At ESA, the emphasis was on minimizing the number of spacecraft used. The Diamond and Z-Array are both DCB configurations in which the one spacecraft serves the function of both collector and combiner. In both cases the beams make multiple hops from collector to combiner to balance the path lengths. Another development was the three-telescope nuller. This is a departure from the DCB, in which the collectors are combined with phases of 0, ±2π/3, and ±4π/3. With three spacecraft, the equilateral triangle is the minimal configuration that still supports phase chopping, but the symmetry leads to undesirable imaging properties. It too uses multiple hops to relay the beams from collector to combiner. The design currently favored is the right- 5
Page 1 and 2: JPL Publication 07-1 Terrestrial Pl
Page 3: Abstract Over the past two years, t
Page 7 and 8: Acknowledgements Twenty-two represe
Page 9 and 10: Table of Contents 1 Introduction...
Page 11 and 12: 4.8.3 Post-Nulling Calibration.....
Page 13 and 14: 6.4.5 Double Fourier Interferometry
Page 15 and 16: I NTRODUCTION 1 Introduction Over 2
Page 17: I NTRODUCTION et al. 2004), and res
Page 21: I NTRODUCTION 1.4 References Angel,
Page 24 and 25: C HAPTER 2 0.7 to 1.5 AU scaled by
Page 26 and 27: C HAPTER 2 Table 2-2. Illustrative
Page 28 and 29: C HAPTER 2 Classical interferometry
Page 30 and 31: C HAPTER 2 trivial in the absence o
Page 32 and 33: C HAPTER 2 Figure 2-3. Simulated mi
Page 34 and 35: C HAPTER 2 would be in atmospheres
Page 36 and 37: 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
Page 75 and 76:
Page 77 and 78:
Page 79 and 80:
Page 81 and 82:
Page 83 and 84:
Page 85 and 86:
Page 87 and 88:
Page 89 and 90:
Page 91 and 92:
Page 93 and 94:
Page 95 and 96:
Page 97 and 98:
Page 99 and 100:
Page 101 and 102:
Page 103 and 104:
Page 105 and 106:
Page 107 and 108:
Page 109 and 110:
Page 111:
Page 114 and 115:
C HAPTER 5 Heavy launch vehicle. Th
Page 116 and 117:
C HAPTER 5 5.3.2 Combiner Spacecraf
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-
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
Page 147 and 148:
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
Page 171 and 172:
Page 173 and 174:
F UTURE D EVELOPMENTS 7 Preparatory
Page 175 and 176:
F UTURE D EVELOPMENTS • To comple
Page 177 and 178:
F UTURE D EVELOPMENTS Table 7-1. Pr
Page 179 and 180:
D ISCUSSION AND C ONCLUSION 8 Discu
Page 181 and 182:
Appendices 167
Page 183 and 184:
T E C H N O L O G Y A DVISORY C O M
Page 185 and 186:
F L I G H T S YSTEM C ONFIGURATION
Page 187:
F L I G H T S YSTEM C ONFIGURATION
Page 190 and 191:
A PPENDIX C 2. Identical FACS fligh
Page 192 and 193:
A PPENDIX C 2. Recall that the coef
Page 194 and 195:
A PPENDIX C Once the formation has
Page 196 and 197:
A PPENDIX C Figure C-3. Example of
Page 198 and 199:
A PPENDIX C Figure C-4. FAST Flight
Page 200 and 201:
A PPENDIX C The “true” time of
Page 202 and 203:
A PPENDIX C References Cohen, S., a
Page 204 and 205:
A PPENDIX D DC DCB DM DM DOCS DOD D
Page 206 and 207:
A PPENDIX D NaCl NAR NASA NASTRAN N
Page 208 and 209:
A PPENDIX E Appendix E TPF-I Review
Page 210 and 211:
A PPENDIX F Alice Quillen, Universi
Page 212:
A PPENDIX F Figure 3-1 - Original f
show all

TPF-I SWG Report - Exoplanet Exploration Program - NASA

Create successful ePaper yourself

Delete template?

Save as template?