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Spectral Analysis of Spectral Analysis of atmospheres by atmospheres by
nulling nulling interferometry interferometry
Marc OLLIVIERMarc OLLIVIERInstitut d’Astrophysique Spatiale - OrsayInstitut d’Astrophysique Spatiale - Orsay
Nulling Nulling interferometry : interferometry :
principlesprinciples
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 22
Beam combiner
T2T1
DD.sin
Star Planet
+
1 arcsec
=10m, D=10m, =0.1 arcsec
Nulling interferometry : Nulling interferometry : key-issues : perfect key-issues : perfect
matching of the wavefrontsmatching of the wavefrontsPhase matchingPhase matching
Co-phasing of the wavefront : optical Co-phasing of the wavefront : optical delay lines + fringe sensordelay lines + fringe sensor
Perfect coherence of the stellar wavefront Perfect coherence of the stellar wavefront : optical filtering + AO if necessary: optical filtering + AO if necessary
Polarization matchingPolarization matchingControl of polarization rotation over the Control of polarization rotation over the optical benchoptical bench
Amplitude matchingAmplitude matching
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 33
Planetary observations : Planetary observations : requirementsrequirements
Planets around a G0 star at 10 pcPlanets around a G0 star at 10 pc
V (0.55μm) / V (0.55μm) / L (3.5μm)L (3.5μm) / / N (10.2 μm)N (10.2 μm) Bands Bands
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 44
Hot Jupiter
Super planet
Real Earth
Real Jupiter
Uranus
Distance to the star (mas)
5 100 100 520 2000
Telescope diameter (m)
20
150
400
1
7
20
1
7
20
0.2
1.4
4
0.05
0.4
1
Planetary flux (mJy)
0.86
2.16
1.1
3 e-4
1 e-4
1.3 e-3
3 e-5
1 e-5
1 e-4
5 e-5
1.5 e-5
3 e-5
5 e-7
1.5 e-7
2 e-8
Contrast star/planet
35000
4000
1200
1e+8
1e+8
1e+6
1 e+9
1 e+9
1e +7
6 e+8
6 e+8
4 e+7
7 e+10
7 e+10
7 e+10
A few interesting photons, a lot A few interesting photons, a lot of noiseof noise
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 55
Signal : ~ 10 ph s-1 m-2 (in the [6-20 m] spectral range)
background and noise
Stellar leaks (star size + pointing stability)Vary as 2 to 6 (and more cf. Rouan)
IR background (locl zodi + instrument emission
Exo-zodi (global emission x interferometre response)
~ 10 to 100 x Signal
~ 1000 x Signal
~ 300 x Signal
Several Several configurationsconfigurations
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 66Angel et al. 1989Mennesson et al. 1997
Internal modulation Internal modulation (Mennesson et al.)(Mennesson et al.)
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 77
Sub-arrays Transmission map 4
transmissioncentral symmetry conjugaison
Modulation efficiency
- Contribution of Exo-zodi and stellar leaks are the same in the 2 states of modulation- Fast modulation (faster than rotation) post détection.- Inherent modulation (Absil)
/2
/2
Detector
Detector
Illustration : courtesy O. Absil
What is observed ?What is observed ?Single pixel detector with :Single pixel detector with :
Planetary signal (modulated)Planetary signal (modulated)Mean stellar leaks (not modulated)Mean stellar leaks (not modulated)Mean exo-zodi signal (not modulated)Mean exo-zodi signal (not modulated)Local zodi (not modulated)Local zodi (not modulated)Variable stellar leaks : pointing + Variable stellar leaks : pointing + asymmetry of the star (variable)asymmetry of the star (variable)Variable exo-zodi signal (asymmetry of Variable exo-zodi signal (asymmetry of exo-zodi)exo-zodi)Other sources of noise (Thermal noise, Other sources of noise (Thermal noise, instrumental noise, detection noise)instrumental noise, detection noise)
Image reconstruction software Image reconstruction software necessary to get F(α,δ,λ) using multi necessary to get F(α,δ,λ) using multi baseline / λ information (Thiébaut et al.)baseline / λ information (Thiébaut et al.)
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 88
Scientific products of nulling Scientific products of nulling interferometryinterferometry
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 99
(After Mennesson et Mariotti 1997)
« Imaging » Spectral analysis
Nulling interferometry Nulling interferometry in the labin the lab
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1010
Booth, Martin and Loya, 2008
JPL’s PDT facility
Nulling interferometry Nulling interferometry in the labin the lab
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1111Chazelas, 2006
Stability of the Stability of the nullnull
1/F noise1/F noise
Need for control loops to stabilize the nullNeed for control loops to stabilize the null
Control loop based on the interferometric Control loop based on the interferometric signal instead of metrology signal (to avoid signal instead of metrology signal (to avoid differential effects)differential effects)
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1212
IAS test bench : IAS test bench : synapsesynapse
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1313
Stability of the null Stability of the null (Gabor et al;)(Gabor et al;)
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1414
ddm
ddm
N
+
-
t
t
N2 N3N1
N
Toward a space Toward a space mission ?mission ?
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1515
Planetary observations : Planetary observations : requirementsrequirements
Planets around a G0 star at 10 pcPlanets around a G0 star at 10 pc
V (0.55μm) / V (0.55μm) / L (3.5μm)L (3.5μm) / / N (10.2 μm)N (10.2 μm) Bands Bands
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1616
Hot Jupiter
Super planet
Real Earth
Real Jupiter
Uranus
Distance to the star (mas)
5 100 100 520 2000
Baseline (m) 20
150
400
1
7
20
1
7
20
0.2
1.4
4
0.05
0.4
1
Total flux (mJy) 0.86
2.16
1.1
3 e-4
1 e-4
1.3 e-3
3 e-5
1 e-5
1 e-4
5 e-5
1.5 e-5
3 e-5
5 e-7
1.5 e-7
2 e-8
Contrast star/planet
35000
4000
1200
1e+8
1e+8
1e+6
1 e+9
1 e+9
1e +7
6 e+8
6 e+8
4 e+7
7 e+10
7 e+10
7 e+10
2 types of 2 types of conceptsconceptsPreparatory science concept : hot Preparatory science concept : hot
jupiters, brown dwarfs, exo-zodi jupiters, brown dwarfs, exo-zodi characterisationcharacterisation
2 telescope array, Contrast 102 telescope array, Contrast 10-4-4, near IR, , near IR, stability 10stability 10-5-5 no internal modulation = no internal modulation = state of the art nulling performancestate of the art nulling performance
Characteristation of exo EarthsCharacteristation of exo EarthsMultiple telescope arrray, internal Multiple telescope arrray, internal modulation, Contrast 10modulation, Contrast 10-6-6, Thermal IR, , Thermal IR, stability 10stability 10-9-9
(In Europe) Only concept 1 has been (In Europe) Only concept 1 has been completely studied using space agencies completely studied using space agencies standardsstandards
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1717
Mission Mission requirementsrequirements
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1818
Characteristics Prep Sci. Concept Char. Of Earth concept
Spectral band Near IR Thermal IR
Cophasing accuracy (residual opd)
2.5 nm rms 3 nm rms
Interferometric extinction
10-4 10-6
Nulling stability 10-5 10-9
Dephasing accuracy 5 10-3 rad 10-3 rad
Baseline 10-500 m 20-500 m
Satellite guiding A few arcsec A few arcsec
Fine guiding 20 mas 8 mas
Telescope size 30-40 cm 1-3 m
Instrument T 100 K 40 K
Detector T 55 K +/- 1K 10 K
Preparatory science from Preparatory science from spacespace
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 1919
Main funtionalities of the Main funtionalities of the payloadpayload
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2020BDT - 16-17 sept 2008
20
Spectrodetector
s
55 K detection stage +fiber coupling
2.5 nm rmsstability zone
optical head internal laser
metrology
z2
FRAS 1+2 1.0-1.5 µm
resolution on the sky
30 mas
pupil plane 2
beam compressor
D 1
Fringe sensor1+2
0.6–1.0 µm2 nm resolution
I2I1
combining stagephase shift
dODL 11 cm
stroke1 nm
resolut.
Siderostat 1
O 1
D’
O1
Siderostat 2
O2
M
1
O2
combiner
pupil plane 1
beam compressor 1G=D/dD
SNR in nulling SNR in nulling modemode
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2121
nulling instabilty due to :opd stab. : nm rmsflux balance stab. : % rms(pointing stability)
detector noise <Td> et Td + RON optics thermal noise
<To> et To
photon noiseintegration time i
mi
n
ma
x
SNR min in [min max]
parameters :i=10h, D=30 cm, o=0.1, q=0.6, <Td>=55°K, Td=0.1°K rms, <To>=100°K, To=1°K rms, ><510-3 rad, <> < 0.01, =2.5 nm rms, =0.003 rms, RON 10e-
Payload composition Payload composition Beam transportationBeam transportation
Fine Relative Angle Fine Relative Angle
Sensor + actuatorSensor + actuator
Optical delay lineOptical delay line
Achromatic phase shifterAchromatic phase shifter
Optical filtering stageOptical filtering stage
Beam combining stageBeam combining stage
Detection stageDetection stage
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2222
Equipment TRL Note
Hg-Cd-Te matrix 9 Picnic on board HST. In-As-Ga photodiode 9 Used on board SPOT4 for the MIR channel e2v CCD or HAS 4 TRL 9 at usual temperatures, bu t
qualification to 90 K required PZT TTM 4 Idem DL 5 TPD-TNO 40 K tested ODL [9] APS 4 Dispersive or reflective APS tested on
ground with 10-4 to 10-5 nulling level Cesic bench 7 NIRSpec bench, cryo test, MMZ 3 Proved 10-4 null in Synapse breadboard in
K band. Extended MMZ to be tested in Persee in 2008
Optics 9 Gold coating on flat or parabolic smal l mirrors (< 40 cm)
Monomode fibres 4 Compatibility with space an d 90 K to be addressed.
Mission requirementsMission requirementsVariable baselines : Variable baselines :
formation flying : 2 siderostats and a beam combining formation flying : 2 siderostats and a beam combining lab satellitelab satellite
cold gas thrusters cold gas thrusters
2 stage metrology (RF + optical sensor)2 stage metrology (RF + optical sensor)
Fine metrology using the payload signalFine metrology using the payload signal
Thermal control of the instrument : V grooves Thermal control of the instrument : V grooves
Launch at L2Launch at L2
Operations at L2Operations at L2
Cost estimate : 300 M€ (mission) + 80 M€ (payload)Cost estimate : 300 M€ (mission) + 80 M€ (payload)
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2323BDT - 16-17 sept 2008
Equipment TRL Note Thrusters 4 Improvement of existing thrusters with TRL 8 Radio frequency metrology 4 Will be tested in flight with Prisma in 2009 Optical sensor 4-7 CNES R and D at Sodern Free flying GNC 4 First levels tested on Prisma in 2009 Precise ST 4 An hydra based SST. Current status PDR. V-grooves 8 Planck L2 operations 7 Planck
Preparatory mission andPreparatory mission and ESA Cosmic Vision ESA Cosmic Vision
processprocessScience poorly consideredScience poorly considered
Feasability estimated as highly riskyFeasability estimated as highly risky
Cost to highCost to high
Part of the scientific information Part of the scientific information provided by other technicsprovided by other technics
Project not selectedProject not selected
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2424
Characterisation of exo-Earths : why Characterisation of exo-Earths : why is it difficult to design a mission and is it difficult to design a mission and
to estimate the cost ?to estimate the cost ?Targets are not yet identified (size, distance, Targets are not yet identified (size, distance, central star, zodi level…)central star, zodi level…)
Required performance is not well definedRequired performance is not well defined
Estimated performance is not yet achieved in Estimated performance is not yet achieved in the labthe lab
The payload is not well defineThe payload is not well define
Technology is not clearly identified for Technology is not clearly identified for several key-systemsseveral key-systems
Existing technology should be improvedExisting technology should be improved
No space experience for several itemsNo space experience for several items
No such complex systems have already been No such complex systems have already been designed and launcheddesigned and launched
Need for O and A phase studies to define the Need for O and A phase studies to define the mission and identify the required technologymission and identify the required technologyMolecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2525
ConclusionConclusionThe simpliest nulling interferometry mission The simpliest nulling interferometry mission is already a big (huge) space missionis already a big (huge) space mission
The ratio science/cost of a precursor The ratio science/cost of a precursor (preparatory science) is considered as very (preparatory science) is considered as very lowlow
However, the mission concept (payload + However, the mission concept (payload + system + operations) should be system + operations) should be demonstrateddemonstrated
A mission to analyse earthlike planets A mission to analyse earthlike planets cannot be considered is present (future ?) cannot be considered is present (future ?) plans of (European) Space Agencyplans of (European) Space Agency
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2626
« The end justifies the means » « The end justifies the means » phylosophyphylosophy
When everything appears hopeless call the When everything appears hopeless call the « A-team »« A-team »
building of a new international structure building of a new international structure such as in particle physics domain (LHC and such as in particle physics domain (LHC and Higgs boson question) with fundings adapted Higgs boson question) with fundings adapted to big projects ?to big projects ?
Molecules 2008 - 21 nov 2008 - M.O.Molecules 2008 - 21 nov 2008 - M.O. 2727
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