15 mai 2006paris - meeting - iap 1 see-coast project super-earth explorer coronagraphic off-axis...

15 Mai 2006 Paris - Meeting - IAP 1

SEE-COAST projectSEE-COAST projectSuper-Earth ExplorerSuper-Earth Explorer

Coronagraphic Off-Axis Space TelescopeCoronagraphic Off-Axis Space Telescope

P. Riaud J. Schneider et al.

ULg / LUTH / LESIA UNSA / OHP / ETH-Zurich / LAOGGeneva / Amsterdam / TorunCSL / Alcatel


Mission philosophyMission philosophy

For a best characterization of exo-lifes, it is For a best characterization of exo-lifes, it is necessary necessary to have a knowledge of their environmental conditions

Exoplanetology is not « un long fleuve tranquille » e.g.:

Diversity of bodies in the solar system

➢ Migration surprise

➢ Large orbital excentricities surprise

➢ The unexplained radius of HD 209458b

➢ The 2M0535-0546 paradox


Mission philosophyMission philosophy

➢ Coronagraphic Off-Axis Space TelescopeCoronagraphic Off-Axis Space Telescope

✔ Visible off-axis Telescope

✔ 1,5 m in diameter (minimum)

✔ Optimized for High contrast imaging (Coronagraphy)

✔ Ultra-smooth mirror ( WFE /100 rms @ 633 nm )

✔ Low resolution spectroscopy for planetary characterisation in Visible


SummarySummary

➢ Science with COAST

➢ Targets of COAST

➢ Payload Concept

➢ Optical Concept

➢ Expected Performances

➢ Conclusions


Science with SEE-COASTScience with SEE-COAST

➢ Exo-Zodiacal disks

➢ Jupiter-like planets

➢ Super-Earth around nearby stars

➢ Option: High resolution UV imaging


Science with COASTScience with COAST➢ Exo-Zodiacal disks

- Knowledge of stellar and planetary formation- Dust properties and dynamic

Study of the DARWIN targets down to 1-10 ZodiStudy of the DARWIN targets down to 1-10 Zodi



- Inner-Gap detection around Young Stellar Objects- Complete dynamic characterization for nearby associations

(Hydra, Centaurus, Lupus ...)

Dust Density Intensity Dust Temperature

Gennaro D'Angelo / NASA



Example of circumstellar disks discovered with ACS/HST

The radius of the blue disk corresponds to 3d with COAST

HD 107146

Fomalhaut

Kalas et al. 2005



PDS 70 Young K5 star (10 Myr)(Riaud et al 2006)

First detection with a phase-maskcoronagraph on the VLT-NACO

COAST would allow same angularresolution than VLT-PFground-based instrument

But with a better contrastBut with a better contrast

Brown dwarf companion

2.5''

Circumstellar disk

Jet

Circumstellar Disk Survey Mission with COASTDiscard Darwin targets

if the exo-Zodi flux is > 10 Zodi


Targets of COASTTargets of COAST

➢ Exo-Zodiacal disks (DARWIN Targets)

mV<5.5 / d<50 pc / limiting magnitude: 24 mag/ ''2

TPF/DARWIN catalogfor nearby stars (631)

All sky target stars (FGKM)

-90

-60

-30

0

30

60

90

0 90 180 270 360

ecl. longitude [deg]

ecl.

lati

tud

e [d

eg]

Fstars

Gstars

Kstars

Mstars

L2 case

Coast target (V<5.5)

-90.00

-60.00

-30.00

0.00

30.00

60.00

90.00

0.00 50.00 100.00 150.00 200.00 250.00 300.00 350.00

Ecl. Long.

Ecl

. L

at.

COAST first targets (41)


Science with COASTScience with COAST➢ Jupiter-like planets Jupiter-like planet survey with SEE-COAST● First detection of cold giant planets around nerby stars (<25pc)● Detection for planets with separation > 1 AU and < 5AU

COAST bandpass


Science with COASTScience with COAST➢ Jupiter-like planets Jupiter-like planet characterisation, with SEE-COAST

The reflected flux:

Fpl=F , P ,t ~A , P ,t ×Rpl2

Chim. Comp surface ''climate'', etc.

Mpl(RV)


Science with COASTScience with COAST

● First detection of cold giant planets around nearby stars

● Detection for planets with separation > 1 AU and < 5AU

SEE-COAST band pass

Fpl

1.3

CH4 H20

CO2

➢ Jupiter-like planets

CH4CH4


Science with COASTScience with COASTFpl

➢ Atmosphere's transparency

➢ Rayleigh scattering



Polarization (orbital phase 90°)

T = 270 K

thick cloud

Clear Sky

Only for theReflected flux

in the visible- nearIR

Fpl P


Science with COASTScience with COASTFpl P

• For Rayleigh scattering by molecules or haze particles

• => Strong phase dependence expected:inclination = 0o

p=constant & highpos. angle rotates

inclination = 70o

p=high for large separation

• Scattering by clouds produces only little polarization


Science with COASTScience with COASTFpl P

p(90) f(90)• RockyMercury 5-10% lowMars 5-10% low

• cloudy (little scattering.)Venus <5% (–) high Saturn <5% high

• cloudy and Rayleigh scatt.Jupiter 5-20% highEarth 5-20% high

• strong Rayleigh scatteringUranus >15% med.Neptune >15% med.Titan 50% med.



Time variation: example of Neptune

Fpl t


Science with COASTScience with COASTFpl t

➢Time variation for eccentric orbits

50 % of orbits have an eccentricity > 0.35

Time variation of the spectrum along the orbit e.g.: water-dominated planet

and ''ocean Planet''

T = 270 K


Science with COASTScience with COASTFpl t

Surroundings Example: ringsRelevance:

Wrong

from

Rpl

Fth~Rpl2 Tpl

4



Chart flow for planet characterization

x(t), y(t)

orbit

d(t)

Tpl

Spectrum A (λ)

Atmospheric gas composition

Time variation A(t)

Rotation periodSurface morphologySurroundings

If H2O Liquid or vapor (depending on Tpl)

G

|A|

« first guess »

Refining

Rp

l

Primary observables

Mpl

Rayleigh scattering

AxRpl2

F(T,)



Giant planet characterization


Science with COASTScience with COAST➢ Jupiter-like planets

167 extrasolarplanets

First targetsfor COAST

At the time of the mission, new targets will be discovered because of radial velocity survey follow-up and better precision


Science with COASTScience with COAST➢ Jupiter-like planets

Constraints on mass, inclination, eccentricity , Albedo in visibleand presence of CH4 and NH3 compounds

171 extrasolarplanets First targets

for COAST


Targets of COASTTargets of COAST➢ Jupiter-like planets (RV Targets)

RV -> high number of targets with large planet – star separation



➢ Jupiter-like planets (DARWIN Targets)

mV<5.5 / d<50 pc / limiting magnitude: 28 Jupiter@5 AU V mag

21.00

21.50

22.00

22.50

23.00

23.50

24.00

0.00 0.20 0.40 0.60 0.80 1.00 1.20

spectral type (B-V)

V m

ag

Jupiter >1 AU V mag

A0 A5 F0 F5 G0 G5 K0 K5



➢ Jupiter-like planets Jupiter-like planets survey with COAST:

● JWST/MIRI in thermal IR only allows detection of hot giant planets with T>350-400K

● VLT-PF complementarity: visible characterisation with COAST

Giant planets detection around DARWINDARWIN targetsallows quantifying the contamination

effect of these planets in the beam of the interferometer in thermal infrared



➢ Type of planets

2016

Two limitations:

Fluxes ==> planet radius

Angular resolution

==> 1 – 5 UA

Cold Planets



➢ Super-Earth around nearby stars ?High difficulty to detect Earth-like planetsin the visible

Contrast ratio:

Earth ~ 1.7 10-10

3R --> 10-9

Possible detection of ''super'' Earth planetor ''ocean'' planet close to the star

⊕

T

U, N

S

HD 149026

J

Measured

Estimated

+HD 69830

+


Science with COASTScience with COAST➢ Super-Earth around nearby stars ?

Some open questions:

● Ambiguity on planet radius:from Si to C dominated planet,radius increases by a factor 1.3(Grasset et al 2006)

==> ambiguity on Albedo==> need DARWIN to know

the planet radius

● Large planets without or tenuous atmosphere ?

Possible scenario: gas in protoplanetary disk blown offby strong stellar wind: ==> bare giant planet cores ==> Super-Earths with teneous atmosphere



➢ Super-Earth around nearby stars ?

High difficulty to detect Earth-like planetsin the visible

Contrast ratio:

~ 1.7 10-10

Possible detection of ''super'' Earth planetor ''ocean'' planet close to the star

1.7 10-10

4 10-103,6 MEarth

Earth Spectrum


Science with COASTScience with COAST➢ Super-Earth around nearby stars

Targetsfor COAST



Brightness of earth at inner limit of HZ

24.0

25.0

26.0

27.0

28.0

29.0

30.0

31.0

32.0

33.0

0 0.5 1 1.5 2

B-V

V m

ag

nit

ud

e

200 stars < 28.5

P HZ =.5*M7/4

planetary albedo = 0.3phase = 0.5

A5 F0 F5 G0 G5 K0 K5 M0 M5

Habitable Zones defined by stellar mass

0.1

1

10

0 0.5 1 1.5 2

B-V

dis

tan

ce fr

om

sta

r A

U

693 stars inner HZ mid HZ outer HZ Sp.T.

Orbital period P mid = M7/4

inner limit P = 0.5*P midouter limit P = 2.0*P mid

P2/A3 = 1/M

A5 F0 F5 G0 G5 K0 K5 M0 M5

TPF/DARWIN catalogfor nearby stars

200 potential targetsfor rocky planets

Habitable Zone for various stars depending the spectral type




0.1

1

10

100

1000

10000

-2 0 2 4 6 8 10 12 14 16

Apparent V magnitude

Hab

itab

le z

on

e se

par

atio

n (

mas

)

Targetsof COAST

(39)

mv<3.4HZ>200 mas

( case ofSuper-Earth

Planet)




0

500

1000

1500

2000

2500

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8

B-V spectral type

An

gu

lar

sep

arat

ion

(m

as)

HZin

HZout

Targetsof COAST

(39)

A0 A5 F0 F5 G0 G5 K0 K5 M0 M5

The blue losanges are the inner habitable zoneThe red squares are the outer habitable zone


Mission strategyMission strategy ➢ Priority C: Searching Exo-zodiacal light around ~50 stars

Total Time= 25 days

➢ Priority B: Jupiter-like planets characterization ~30 stars

Total Time= 120 days x (7 checking)

➢ Priority A: Super-Earth planets detection ~30 stars

Total Time= 120 days x (7 checking)

➢ Mission duration: ~ 5 years



➢ Option: High resolution UV imaging

✔ Stellar formation in nearby galaxies

✔ Study of O-B, W stars

✔ Magnetic field and plasma processes

✔ Coronagraphy for z<0,2 AGN

Accretion zone and Torus imaging


Science with COASTScience with COAST➢ High resolution UV imaging

✔ Stellar formation in nearby galaxies

✔ Study of O-B, WR stars

- High resolution imaging of stellar formation area(res 17 mas in Ly, FOV 30'' x 30'' )

- WR, O-B stellar statistics- Stellar formation rate

- Heavy elements enrichment



Magnetic field and plasma processes

O star

WR star

Wind interaction zone (UV, X-ray)

Folini & Walder

- Cataclysmic variable study- Wind interaction- Stellar formation area

- Compact objects study- Accretion process

- Variability- Magnetic field estimation

Gain: x 260 with respect to the FUSE mission



✔ Phase Coronagraphy for z<0,2 AGN

✔ Accretion zone and Torus imaging

✔ UV phase-mask coronography (121-146 nm) High contrast imaging of AGN nucleus

Z=0,2 (~750 Mpc) 20 mas => 70 pc


Spacecraft philosophySpacecraft philosophy

✔ UV-Visible off-axis Telescope optimized for HCI

✔ 1,5 m in diameter (minimum) /D<0,1''

✔ Optimized for High Contrast Imaging (Coronagraphy)

✔ Ultra-smooth mirror ( WFE /100 rms @ 633 nm )

rejection factor > 50000 (goal)

✔ Low resolution spectroscopy

for planetary characterisation in Visible


Payload Concept Payload Concept

Electronics andinstrumentationn

Primary mirror ( m )

Secondary mirror ( m )


Instrument (I)Instrument (I)HRCC

Spectral Coverage 500 – 1000 nm

Detector Size 1 – 2048 x 2048Type CCD (red – 16 bis)

DynamicQe ~ 85%

FOV 17'' x 17''IFOV 34 mas

Angular resolution 68 mas

Phase-mask coronagraphy

Readout noise 1 e- / Photon countingDark current 10 e-/h

( High Resolution Coronagraphic Camera )

105

The HRCCHRCC camera (Phase-Mask coronagraphy)- option 1: near-IR channel (1-1.4 m)- option 2: blue channel (0.4-0.6 m)


Instrument (II)Instrument (II)

HRCC WFCC HRI-SUV HRI-LUV

Spectral Coverage 500 – 1000 nm 400 – 1000 nm 92 – 200 nm 200 – 400 nm

Detector Size 1 – 2048 x 2048 1 – 4096 x 4096 4 – 2048 x 2048 4 – 2048 x 2048Type CCD (red – 16 bis) CCD (broadband – 16 bits) MCP (CsRbTe – 12 / 16 bits) MCP (CsRbTe – 12 / 16 bits)

DynamicQe ~ 85% ~ 70% ~ 40% ~ 40%

FOV 17'' x 17'' 1,8' x 1,8' 4 x 13'' x 13'' 4 x 30'' x 30''IFOV 34 mas 27 mas 6 mas 13 mas

Angular resolution 68 mas 55 mas 12 mas 27 mas

Phase-mask coronagraphy Coronagraphy Coronagraphy Coronagraphy

Readout noise 1 e- / Photon counting 2 e- Photon counting Photon countingDark current 10 e-/h 10 e-/h

( High Resolution Coronagraphic Camera ) ( Wide Field Coronagraphic Camera ) ( High resolution Imager – Short UV ) ( High resolution Imager – Long UV )

105 105 105 105

9 104 cnts/s/pixel 8 106 cnts/s/pixel

Two cameras in the visible wavelengthsTwo UV-camera (parallele mode with the HRCC camera)

The priority is the HRCCHRCC camera (Phase-Mask coronagraphy)


Instrument (III)Instrument (III)

● All cameras have various coronagraphic devices

● The HRCCHRCC camera allows simultanous imaging of three different bands (650-760 nm / 750-860 nm / 850-960 nm)

● Each bands can provide three different images for low spectral resolution capabilities (R ~40) and spectral differential imaging (R ~25)

● Three calibration frames (one per band) can be added on the CCD

● The CCD 2048 x 2048 9 to 12 simultanous images

● One of the two HRI cameras can be exploited simultanously in the four extended field of view (option)


Instrument (IV)Instrument (IV)

● Multiple field of view concept

● Optimisation for a larger Field of view

● Problems:

- Instrumental cost - Instrumental weightt - Mirrors coatings (Vis-UV)

But High Science return


Telescope Concept Telescope Concept 1,8 m

3,2 m long+ baffle 0.8 m

Ready for GAIA plateformReady for GAIA plateform

- But too large for COAST !

- Possible GAIA-LITE ?

Mirrors COATING:Mirrors COATING:

- protected silver ?

High qualityfolding mirrors


Mission Requirements Mission Requirements

F G K M0

10

20

30

40

50

60

SEE-COAST detectivity (R=5, SNR>3 in 3 days)

3 Earth radii

1 Jupiter radius HZ

1 Jupiter radius 2xHZ


Spectral type

Num

ber o

f det

ectio

ns (1

29 ta

rget

s)


Optical Concept (I)Optical Concept (I)

● PRIMARY RFELECTOR:● RC= -5435.20883 mm● TH to secondary=3000 mm● K=-1 (Parabola)● Decenter =1200 mm● Aperture= 1500 mm

The design relies on an off –axis parabolic primary mirror. The image is created with a stigmatic relay with a relatively small off-axis secondary relay. Note that there is a strong pupil demagnification, consequently a strong angular magnification.

● SECONDARY RFELECTOR:● RC= -584.883 mm● TH to image=6234 mm● K=-0.8341871 (Parabola)● Decenter =125 mm● Aperture= 200 mm


Optical Concept (II)Optical Concept (II)

Manufacturing accuracy:

✔ GOAL: rms @ 633 nm ~rms per mirror

✔Challenging but already demonstrated for VIRGO mirrors

✔Ion-beam figuring (high accuracy – CSL-AMOS CSL-AMOS ) SiC/ZERODUR)

✔ Need refinements of metrology techniques (direct nulling)

Tolerancing: active secondary+ tip-tilt mirror


Optical Concept (III)Optical Concept (III)example with the AGPM coronagraphexample with the AGPM coronagraph

Phase-Mask coronagraph (FQPM / AGPM) have been added in the Zemax Optical Analysis

The HRCC camera possesses minimum of three wavelength bands

Concave gratingin the primary focal plane

Folding mirror AGPM mask Lyot stop Final image

Wavelength selector2' x 2' FOV


Optical Concept (IV)Optical Concept (IV)Only conical mirrorsOnly conical mirrors low risk designlow risk design

- The two folding (plane) mirrorswith rms already exist

- F/D>60F/D>60

● ok for coronagraphy● ok for the CCD pixel size

- SiC mirror is preferedSiC mirror is prefered

● Low mass / high rigidity● Ion figuring extensively studied● >rms already demonstrated

- Active secondaryActive secondary

● Misalignment correction● Drift correction ( PSF stability)

- Tip-Tilt correctionTip-Tilt correction GOAL 1 mas rms (HST 7-10 mas rms)

Spot diagramfor 27'' x 27'' FOV

Circle:Airy pattern


Optical Concept (V)Optical Concept (V)

Polarization issuesPolarization issues

● Small residual polarization in the pupil plane● The effect on the coronagraphic device must be actively studied


Optical Concept (VI)Optical Concept (VI)● 2. MANUFACTURING AND TOLERANCES (CSL- S. Roose)

The telescope needs to have a WFE lower than λ/100 @ 633 nm.

The preliminary error budget for the manufacturing and AIV is the followingDesign: λ/200 @ 633 nm (TBC)Primary reflector: λ/200 @ 633 nm (TBC)Telescope AIV (on ground): λ/200 @ 633 nm (TBC)Telescope environment (in flight): λ/200 @ 633 nm (TBC)

All other manufacturing errors on other auxiliary optics are currently disregarded, but we need to assume higher effort on smaller apertures.

● Primary reflector manufacturing:

Polishing up to λ/200 @ 633 on an aperture of 1500 m is fundamentally not a problem. A development of a measurement tool (interferometer) with an absolute WFE accuracy of typically better than λ/400 @ 633 nm. The primary reflector shall be characterized in a ZERO-g configuration, with representative (very critical) supporting hardware. The polishing procedure shall probably compensate for the deformation obtain in the used position of the telescope.

A coronagraph WFE analysis should typically analyze the effect of tri-fold aberration and hexagonal print-through. These aberrations will be specified with a DSP and each Zernike coefficient up to 36.

The design of a supporting cell shall be done in close collaboration (iteration) of the telescope design and combined FEM analysis. In this respect the appropriate choice of the mirror material should be traded off: ZERODUR or/and C-SIC.


AIV on groundAIV on ground

A development of a measurement tool with an absolute WFE accuracy of typically better than λ/400 @ 633 nm is requested for this operation.

The telescope WFE or PSF shall be measured. The telescope shall be characterized in a ZERO-g configuration, with representative (very critical) supporting a hardware.

It is recommended that primary reflector mechanical design and telescope design and integration shall be under a unique responsibility, and this in order to avoid conflict situations.

Provided that specific tooling (shimming and micrometer screws) the mirror manufacturing errors (radius of curvature and decentring) can be compensated.

The alignments residuals are of order of 10 μm and 1 arcsec. Note that these operations shall be performed in a controlled and regulated environment close to 20°C (TBC).


Tolerancing (I)Tolerancing (I)● Tolerancing with Zemax (TM)

- X, Y, Z = 10 m WFE =0,01 (90%) Active secondary- Tip-Tilt = ~1'' (~20 cm in diameter)

● Not too low lighten primary mirror

Two technologies are possible: SiC and ZerodurIn both cases: warning with the mirror mounting

● Example with the FUSE mission: WFE 0,02 rms


Tolerancing (II)Tolerancing (II)

Mounting issuesMounting issues

● Small residual WFE after mounting● Coronagraphic and interferometric tests only after full assembly


Telescope environment Telescope environment

Given the tight alignment tolerances on ground, one should test the alignment of the telescope in representative thermal environment.

A specific thermal balance test shall be combined with a WFE measurement. One of the objectives is to validate the operation of (active or passive) thermal regulation (focus combination) and to estimate the temperature for optimal WFE.

In order to compensate for (thermo-elastic) bending and decentring it is interesting to implement and active secondary mirror. This will require a metrology system with arcsec resolution.

The final goal with thermal control and active secondary mirror is to maintain the WFE into specification

(Consider this as within a volume of better than 5 μm and 0.5 arcsec relative primary versus secondary reflector position).


Straylight / baffle Straylight / baffle ● Straylight / Baffle

As in most telescopes, requiring a very high SNR, an optical baffle needs to be foreseen. This could be either a part of the telescope structure (XMM-OM) and participate to the thermal control, or as for COROT the baffle is isolated from the telescope structure. The first solution is preferred for structural reasons. Indeed, the particulate contamination requirements might impose the presence of a door in front of the telescope baffle.

● CONTAMINATION HANDLING

COAST will operate in the VIS-UV. What concerns molecular contamination, the integration and testing of the FM telescope shall be done in controlled environment.

The particulate contamination will impose to integrate and test the telescope in a class 100 environment. The particulate contamination will also determine the presence of a door in front of the aperture.

The TIS formula gives for 100 ppm dust comtamination (COROT telescope) a level of light scattering : 10-8


Mirrors Coating Mirrors Coating ● Protected Silver (best for the visible)

- Allows high throughput on 400-1500 nm wavelength (98% fresh coating)- Low reflectivity bellow 350 nm(<50%) due to surface plasmon resonnance

● Protected Aluminium (best for UV)

- Allows medium throughput on 400-1500 nm wavelength (80-90% fresh coating)- high reflectivity bellow 350 nm(>70%)

( © Denton Vaccum USA )


Mission philosophy Mission philosophy ● Nearly Full tested telescope before launch

To performe a best coronagraphic device, it is necessary to performe some tests during AIV facility (problem: COST)

Active optique seems to be necessary for:

- Fine centering with tip-tilt mirror: 0,5 to 1 mas repeatability needed- Global alignment with active secondary: Coma and focusing capabilities

● Adaptive Optics (AO)

- Not before the coronagraphic device: ● High complexity (phase and amplitude corrections) / low throughput● Coronagraphic limitation but not the wavefront correction in the large band

- Possible after the coronagraphic device:● Not coronagraphic limitation● Relaxing the wavefront bumpiness of the AO optics● Medium throughput / but High complexity


Mission philosophy Mission philosophy

Adaptive Optics = CalibrationAdaptive Optics = Calibration

The main speckle limitation is the phase retrievial accuracy

● Both for AO system of calibration in the final coronagraphic image

● The final calibration in the final coronagraphic image:

- More throughput than AO system- Some optical schemes exists: multi-wavelength imaging , Zimpol

- if the speckle realisation is faster than 1 minute, it seems to be more accurate to use AO system.

● The case of L2-orbit allows high stability Open issue: in the case of 10-10 level , what the speckle coherence time ?


Optical Concept (I)Optical Concept (I)

➢ Why Phase-Mask Coronagraphy ?

-- Need a good Need a good Inner Working AngleInner Working Angle

- Need a sufficient phase shift achromatisation (R~5) phase shift achromatisation (R~5)

- WFE=/100 rms rejection on the peak ~ 5 10rejection on the peak ~ 5 1044 – 10 – 1055

=3 10=3 10-3-3 rms rms on the on the phase shift seems to be sufficient A < 0,5%A < 0,5%

The AGPM coronagraph can be fullfill all requirements ... ( Problem: Zero Order Grating manufacturing ... )


Optical Concept (II)Optical Concept (II)

New coronagraphic deviceNew coronagraphic device (Roddier & Roddier 1997, (Roddier & Roddier 1997, Rouan et al. 2001, Riaud et al. 2001,2003, Mawet et al. 2005ab)Rouan et al. 2001, Riaud et al. 2001,2003, Mawet et al. 2005ab)

- Allows good Inner Working Angle (< 1.5 D) (150 mas)

- High nulling efficiencyHigh nulling efficiency 120000 has been demonstrated 120000 has been demonstrated (Riaud et al. 2003)(Riaud et al. 2003)

- Extensively studiedExtensively studied

● A Four Quadrant Phase Mask (FQPM) avalaible on the VLT-NACO

● Chromatic problem of the phase shift extensively studied

Riaud et al. 2001, Riaud & Lemarquis 2003, Riaud Thesis, Mawet, Riaud et al. 2005ab and 2006 Quarter-wave mirrors, dispersive plates, birefringente plates, Zero Order Gratings

● Good result in the visible with first achromatic prototype (R=2)

➢ Phase-Mask Coronagraphy


Optical Concept (III)Optical Concept (III)➢ Phase-Mask Coronagraphy

FQPM(mono)

AGPM(poly)

10-6

10-6

Lyot Stop

Lyot Stop


Optical Concept (IV) Optical Concept (IV)

AGPM coronagraphAGPM coronagraph

- No « dead zones »

- Azimuthally symmetric

- ZOG achromatization possibleZOG achromatization possible

● The polarization mismatch must be checked with optical simulations

➢ Phase-Mask Coronagraphy


Optical ConceptOptical Concept (V)(V)➢ Phase-Mask Coronagraphy

Ex: Coronagraphic results in K band (VLT-PF prototyping)WFE of /70 rms both polarizations (vectorial analysis)Residual chromatismAmplitude mismatches

3.3 μm740 nm305 nmGrating period (C)

3.3×10-71.4×10-72.9×10-7Contrast at 3λ/d

4×10-51.7×10-53.5×10-5Null Depth (global)

N (R=4.86)

K (R=5.5)

Ic (R=5)

Filters

Speckle level

3 λ/D


Optical ConceptOptical Concept (VI)(VI)

➢ Manufacturing issues in the visible-- Need a median index value (n>1,6 and n<2,0) Need a median index value (n>1,6 and n<2,0)

Ex: n=1,81 --> high index glass

● Grating pitch ~ 360 nmGrating pitch ~ 360 nm● Grating depth ~ 2,6 µmGrating depth ~ 2,6 µm● Filling factor ~ 70%Filling factor ~ 70%

➢ Allows small reflexion lostAllows small reflexion lost➢ Good nulling > 10Good nulling > 1055, R~6, R~6➢ Glass molding technique ?Glass molding technique ?

=600-1300 nm with 4 masks=600-1300 nm with 4 masks


Expected PerformancesExpected Performancespreliminary resultspreliminary results

AGPM coronagraphic simulationAGPM coronagraphic simulation

● Speckle (rms @ 633 nm) / photon / readout noises● Blue: 650-760 nm / Green: 750 nm-860nm / Red: 850-960 nm● Rejection on the peak ~50000 in the three bands

Polychromatic COAST PSF (=0,1) Polychromatic COAST Coronagraphic image (=0,5)


650-750 nm740-860 nm850-960 nm

Raw Residuals

Residuals after ref subtraction

Numerical simulationsNumerical simulations

- Nulling: 50000 peak to peak

● Gain with HST: ~10000 !!!● IWA: >2D (0.3'')

- Only Reference subtractionOnly Reference subtraction

● Allows Exo-Zodi detection● Jupiter-like planets

- Multi-wavelength subtractionMulti-wavelength subtraction

● Jupiter-like planets● ''super'' Earth ?● ''ocean'' Planet ?

- - ''Coherente'' subtraction subtraction

- ZIMPOL subtraction


Residuals after ZIMPOL subtraction ?


Multi-wavelengths imagingMulti-wavelengths imaging

● Simultanous imaging● Self-calbration

- limitationslimitations

● Chromatic smearing● No-common path errors● A contrast of > 108

is reached at 6D

Need global studyof the speckle noise

Chromatic speckles residuals image (=0,33)

Blue: speckle noise band 1 - band 2Green: speckle noise band 2 - band 3Red: speckle noise band 3 - band 1



Planets detection image (=0,33)

Planets detection image (=0,33)

Planets detection image (=0,33)Planets detection image (=0,33)

10-9

5.10-10

Centro-symmetrical subtraction Comparison between the planet fluxand the speckle noise in the three

different bands




Multi-wavelengths imagingMulti-wavelengths imaging

● Simultanous imaging● Low resolution spectroscopy (R~40)● Differential imaging

If the planet contains some spectral features:

The differential imagingincrease the detectivity of planet

Also applicable for giant planetswith CH4 and NH3 compounds

Earth Spectrum


Expected Performances Expected Performances ➢ The CoastSimCoastSim implementation


Expected PerformancesExpected Performances ➢ The CoastSimCoastSim implementation

-- CoastSim is now avalaible (v 1.1)CoastSim is now avalaible (v 1.1)

- The code has already been experimented for JWST/MIRIcoronagraphy

- The code include:The code include:

● Stellar spectra, Earth spectrum, Jupiter spectrumStellar spectra, Earth spectrum, Jupiter spectrum● Burrows and Allard spectraBurrows and Allard spectra● Phase-mask coronagraphic implementation (FQPM, AGPM and AIC)Phase-mask coronagraphic implementation (FQPM, AGPM and AIC)

- Must be extensively tested with all theMust be extensively tested with all the DARWINDARWIN targetstargets

● Wait telescope inputs (wavefront bumpiness) for a best representative simulation



We take into account:We take into account:

● WFE (DSP: f-1.5)/100 rms @ 633 nm● Amplitude error of 0.5 % on the primary mirror● Jitter: 1 mas rms● Pointing accuracy: 1 mas● Residual phase-shift and amplitude error on the AGPM● Bandpass (R=5)

● Zodiacal and Exozodiacal light (10 Zodi)● Readout (2 e-) and dark noises (0.001 e-/s)● Gain after reference subtraction -> worst case ~10



or HZ

or 2x HZ

or 4x HZ

( Super Earth in HZ )

Jupiter to Super-Earth like planets

Detection of cold giant planets

(> 1 AU and < 5AU)

around nearby stars


Expected Performances Expected Performances Simulation inputsSimulation inputs

● Stellar and planet spectra● Zodi and Exo-Zodi noises● CCD noises● 628 DARWIN targets

The S/N is the average of the S/Nin the three bands

● Worst case: only reference subtraction not multiwavelength analysis

● Some examples with:

Jupiter-like planets''super'' Earth planets (8 MEARTH = 2 REARTH)

Exposure timeoptimization needed

Spectral bandwidth: R=5


Expected Performances Expected Performances





Exposure timeoptimization needed CoastSim is ready but :CoastSim is ready but :

● Add the telescope DSP● Add powerfull subtraction analysis● Add planetary B-V flux

This first signal to noise simulationshows good opportunities to detectExo-Zodiacal dust down to 1-10 Zodiand Jupiter-like planets.



Expected Performances (I)Expected Performances (I)

F G K M0

10

20

30

40

50

60


3 Earth radii

1 Jupiter radius HZ



Spectral type

Nu

mb

er

of d

ete

ctio

ns

(62

8 ta

rge

ts)

F G K M0

10

20

30

40

50

60


3 Earth radii

1 Jupiter radius HZ



Spectral type

Num

ber

of d

etec

tions

(62

8 ta

rget

s)

CoastSim for DARWIN targets :CoastSim for DARWIN targets :

● 628 targets● Reference subtraction (Gain~10)● Long integration time: 3 days


Expected PerformancesExpected Performances ➢ Targets optimization

- After CoastSim simulation -> choice of 100 best targets

- Adding RV first best targets (12)

- Waiting for others RV targets

- Adding TPF best targets (17)

---------------------------- 129 primes COAST targets129 primes COAST targets -------------------------

● Need telescope tolerancing Need telescope tolerancing for a best representative coronagraphic simulations

● Actually: Worst case with a mirror DSP of f -1,5 and 100 ppm of dust


Expected Performances (II)Expected Performances (II)

CoastSim with dust on the mirror :CoastSim with dust on the mirror :

● 129 best targets● Reference subtraction (Gain~10)● The ''habitable Zone'' depends on the stellar spectral type

F G K M0

10

20

30

40

50

60


3 Earth radii

1 Jupiter radius HZ



Spectral type

Nu

mb

er

of d

ete

ctio

ns

(12

9 ta

rge

ts)

F G K M0

10

20

30

40

50

60


3 Earth radii

1 Jupiter radius HZ



Spectral type

Nu

mb

er

of d

ete

ctio

ns

(12

9 ta

rge

ts)



Worst case: only simple reference subtraction

To increase performances:To increase performances:

● Need multi-spectral imaging (Gain>10)● Need polarization imaging (ZIMPOL)

- Possible Gain ~ 100 - Need to limitate the depolarization issue - Efficient if we have an information on the ''flat'' ~10-3


ConclusionsConclusions

● Exo-zodiacal and Giant planets detection around DARWINDARWIN targets

allows quantifying contamination effect of these features in the beam of the interferometer

● Detection of ''super'' Earth ? in the habitable zone of a selected sample of bright stars (39)

● Rich science with high resolution UV imaging

● Minimum mirror diameter 1,5 m The gain of detectivity is ~D2 in visible and UV

15 mai 2006paris - meeting - iap 1 see-coast project super-earth explorer coronagraphic off-axis...

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