spectral analysis of atmospheres by nulling interferometry marc ollivier institut d’astrophysique...

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


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


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


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.)


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.)


Scientific products of nulling Scientific products of nulling interferometryinterferometry


(After Mennesson et Mariotti 1997)

« Imaging » Spectral analysis

Nulling interferometry Nulling interferometry in the labin the lab


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)


IAS test bench : IAS test bench : synapsesynapse


Stability of the null Stability of the null (Gabor et al;)(Gabor et al;)


ddm

ddm

N

+

-

t

t

N2 N3N1

N

Toward a space Toward a space mission ?mission ?


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


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


Mission Mission requirementsrequirements


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


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


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


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


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


« 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 ?


spectral analysis of atmospheres by nulling interferometry marc ollivier institut d’astrophysique...

Documents

x signal slide

absil slide

arcsec slide

lab molecules

lot of noise molecules

synapse molecules

principles molecules

configurations molecules