Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
François Hénault UMR 6525 H. Fizeau, Université de Nice-Sophia Antipolis Centre National de la Recherche Scientifique Observatoire de la Côte d’Azur Parc Valrose, 06108 Nice – France
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Three reasons to build space nulling telescopes • Usable for exploratory science missions: exo-zodiacal clouds characterization, hot and cold Jupiter-like planets… • Allows validating most of Darwin/TPF-I required technologies (achromatic phase shifters, WFE filtering, OPD control…) • If rotating, allows validating the envisioned algorithms for planet finding and characterization
Previous publications • “Fibered nulling telescope for extra-solar coronagraphy,” Optics Letters 34, n° 7, p. 1096–1098 (2009) • “Simple Fourier optics formalism for high angular resolution systems and nulling interferometry,” JOSA A 27, p. 435-449 (2010) • “PSF and Field of View characteristics of imaging and nulling interferometers,” Proceedings of the SPIE 7734, p. 773419 (2010) Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Super-Resolving Telescope (SRT) Monolithic telescope Secondary Mirror Metrology beam 1
Metrology beam 2
APS 1
(P) Primary Mirror
Relay optics Converging optics Diverging optics FoldFoV mirror Rotator Beamsplitter Acromatic Phase Shifter
Multi-axial combiner (exit pupil plane)
APS 2
(P’) P’1
O’ B’
P’2 F’
Focal plane
Z Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
X” SMW Array Y”
Z San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Sheared-Pupil Telescope (SPT) Monolithic telescope Secondary Mirror APS 1
APS 2
(P) Primary Mirror
Relay optics
Multi-axial combiner
O’
Lyot stop in F’ exit pupil plane
Focal plane
X” SMW Arra y
Y” Z Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
(P’)
P’2
P’ 1
FoV Rotator
Metrology beams
Z San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Two different types of nulling telescopes Input pupil plane
Output pupil plane Y ’
Y
Unmasked output sub-pupils (SRT)
O
All input and output sub-pupils are identical and optically conjugated
Masked output sub-pupils (SPT)
D’
X
O’
X’
D
Y
D
O
Monolithic pupil telescope
X
B Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
D’
B’ Y ’
O’
Lyot stop in exit pupil plane X’
B’ San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Analytical expression of SRT nulling maps • Star leakage into SMW pointed along direction s ˆ PS (s) = IS G * (s) ⊗ B ( s ) a exp [ i φ ] exp − i k s O' P' / m ∑ n D n n n =1 N
[
2
]
• Planet signal coupled into SMW ˆ (s) ⊗ ∑ a exp[i φ ] exp − i k s O' P' / m PP (s) ≈ I P G * B D n n n n =1 N
[
2
]
• Where: – – – – – – –
G(s) : SMW filtering function ˆ (s ) B D : complex amplitude generated by one single sub-pupil, back projected onto the sky an : amplitude transmission factor for sub-pupil #n ϕn : phase-shift for sub-pupil #n k = 2π/λ where λ is the monochromatic wavelength O’P’n : coordinates of sub-pupil #n m : optical compression factor of relaying optics (= D’/D)
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
SPT nulling maps • Star leakage into SMW = ideal null + “null floor” N0 2
N
∑a
PS (s) = IS
n
exp[i φ n ] + N 0
n =1
• Planet signal coupled into SMW N
PP (s) ≈ I P
∑a
n
[
exp[i φ n ] exp i k s OPn
]
2
n =1
• Signal to Noise Ratio (SNR) SNR (s) ≈
Effective collecting area
PP (s) η A τ
Integration time
[PS (s) + N 0 IS + I EZ ] η A τ + σ 2N
Exo-zodiacal cloud / Background Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
Detection noise San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Example of SRT numerical simulation
IW
Nulling map
SRT exit pupil 1.E-2 !
5 SNR map
Star leakage
A
4 arcsec
B=3m
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
SPT numerical simulation
IW
Nulling map
SPT effective entrance pupil
2 Constant, equal to nulll floor 1.E-4
SNR map
Star leakage
A
4 arcsec
D=5m
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
SNR sensitivity curves 10
8
SRT (B=2m) SPT (B=3m)
6
SPT (B=2m)
4
3 2
0 4
6
8 8
10
12
SRT (B=3m)
Signal to Noise Ratio
Signal to Noise Ratio
Magnitude of target star
SRT (B=3m)
Integration time in minutes
10
SRT (B=2m)
8
SPT (B=3m) 6
SPT (B=2m)
44 2
0 0
10 10
5
Magnitude of target star
30
SRT (B=2m) SPT (B=3m)
4
SPT (B=2m)
33 2 1 0 5.0E-04
1.E-3 1.0E-03
1.5E-03
2.0E-03
Exo-zodi/star flux ratio
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
SRT (B=3m)
Signal to Noise Ratio
5
Detection noise in # electrons
Signal to Noise Ratio
25
4 SRT (B=3m)
Background/ Star flux ratio
20
Integration time (mn)
6
0.0E+00
15
SRT (B=2m)
3 3
SPT (B=3m) SPT (B=2m)
2
1
0 0
2020
40
60
80
100
Detection noise (electrons)
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Performance vs. shear/entrance baseline B 10
SRT2
0.6
0.4
0.2
0 0
1
2
3
4
5 5
Signa to Noise Ratio (SNR) Signal to Noise Ratio
0.8
SRT2
SRT4
SPT cut-off
Radiometric efficiency
Radiometric efficiency
1
SRT8 SPT2 SPT4 SPT8
6
7
8
9
10
SRT4
8
SRT8 6
SPT4 SPT8
SPT
4 4
2
0 0
2.5Entrance baseline B (m)
1
2
Entrance baseline B (m)
Entrance baseline B
3
4
5
6
7
8
SRT8 SPT2 SPT4
SRT
0.6
0.4 0.4
SPT8
0.2 0.2
0 0
1
2.5
2
3
4
5 5
6
7
8
10
9
10
Entrance baseline B (m)
Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
SRT2 SRT4
8.E-04
Null floor + star leaks
SPT
SRT4
Null floor & Star leaks
1.E-03
SRT2 0.8
9
Entrance baseline B
1
Inner Working Angle (arcsec) Inner Working Angle (arcsec)
SPT2
SRT
6
SRT8
Only at few locations in SRT focal plane
6.E-04
SPT2 SPT4 SPT8
4.E-04
2.E-04
1E-4 0.E+00 0
1
2
3
4
5
6
7
8
9
10
Entrance baseline B (m)
San Diego, 08-23-11
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Imaging power of multi-fibered nulling telescopes for extra-solar planet characterization
Conclusion • Both concepts of nulling telescopes seem suitable for hot Jupiters and exo-zodiacal clouds characterization • SRT and SPT show adverse advantages and drawbacks: – SRT Better radiometric and SNR performance, smaller Inner Working Angle (IWA), but suffers from non-uniform nulling rates – SPT Better and uniform nulling rates, but limited by larger IWA and lower SNR (requires longer integration times)
• Possible remedies: – Adjustable/removable Lyot stop in the exit pupil plane – Use “blinded” SMWs to calibrate and subtract SRT stellar leaks – Add anamorphic optics into the optical train… Conf. 8151 Techniques and Instrumentation for Detection of Exoplanets V
San Diego, 08-23-11
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