The Fresnel Diffractive Imager project---

Principles, Instrumentation and Mission scenarios

Laurent Koechlin, Denis Serre, Paul Deba,Truswin Raksasataya,Christelle Peillon,

Emmanuel Hinglais, Paul Duchon,Pierre Etcheto,Christian Dupuy,Benoît Meyssignac,Laurent Doumic.

Université de Toulouse,CNRS France

The Fresnel Diffractive Imager projectI. Optical Principles

Focalization by diffraction

Chromatic correction

High dynamic range

III. Space mission scenarios

Primary array vessel design

Focal instrumentation design

Orbits and Formation flying configuration

IV. Astrophysical targets

Some of the possible scenarios

II. Lab prototype, optical and numerical testsOptical setup

Tests results on artificial sources

Tests planned on sky sources

Numerical simulations for large arrays

I. Optical Principles

focus

Order 0 : plane wave

Lens (or miror): focusing by refraction (or reflexion)

Fresnel array: focusing by diffraction …

Focalization : different ways

Plane wavefront

Order 1 : convergent

focus

Lens

Concentric geometry (Soret 1875)

Efficiency at order 1: 10%

Exemple for 15 Fresnel zones

2D radial expansion

Orthogonal geometry (2005)

Efficiency at order 1: 4 to 8 %

2D Cartesian expansion

g(x)= 1 si (x2 +f2)1/2 [(f/m+ (k-off)+1) m ; (f/m+ (k-off)+1)

m[

sinon g(x) = 0Transmission (x, y) = g (x) xor g (y)

Fresnel Zone plate or Aperture synthesis array ? (here: 1740 ouvertures)

Exemple for 30 Fresnel zones

circular geometry => isotropic PSF

Image

Image formation

non linear luminosity scaleIn order to show the faint isotropic rings.

Aperture

Orthogonal geometry => orthogonal PSF

Transmission: g(x) g(y)

Image formation

non linear luminosity scaleIn order to show the faint spikes.

Image

Aperture

Quasi no stray light except in the spikes.

Case of a second source in the field:

Image formation

Image formation

Case of a second source in the field:

Image formation

Case of a second source in the field:

Comparison: Fresnel arrays versus a solid aperture

1500 Fresnel zones

Images of a point source by:

150 Fresnel zones

Solid square aperture

luminosity scale:Power 1/4 to show

spikes

"for" Fresnel Arrays:

No mirror, no lens to focalize : just vacuum and opaque material. => a potentially very broad operational domain: 90nm - 25 m

Large tolerance in positioning of subapertures for /20 wavefront quality:

100 m in the plane of the array10 cm in the wave propagation direction (perp. to

array)The tolerance is wavelength independent

=> Opens a way to build very large aberration-free apertures for astrophysics.

High dynamic range: 108 on compact objects for a 300 zones array

Angular resolution: as high as with a mirror the size of the whole array.

"against" Fresnel Arrays:

Chromaticity... corrected by small diffractive lens after focus, (order 1 chromaticity cancelled by order -1 chromaticity),but bandpass limitations remain: = √2 S/C

Low transmission compared to a mirror : t = 5 to 10%

kilometric focal lengths => requires formation flying in space

F = C2/8N

C

10 to 100 km

Optical scheme of the Fresnel Diffractive Imager

Diffractive lens at order -1

e.g. 10 cm Field Opticse.g. 2m

Img. plane 2 : achromatic

Primary Fresnel arraye.g. 20 m

pupil plane

Spacecraft 1 holding primary Fresnel array

Spacecraft 2 holding focal instrumentation

mask

image plane 1dispersed

Order 1 rays, focused by primary array

Order 0 rays

Converging lense.g. 10 cm

Focal Instrumentation

The field - bandpas compromise

Chromatically aberrated beam at prime focus

Field delimited by field mirror

The chromatic correctordoes a good job,but it corrects only what it collects.

II. Lab prototype, optical and numerical test results

Prototype built at Observatoire Midi Pyrénées in Toulouse2006 - 2008

Lab Prototype: light source module

• Étoiles doubles

photo

• Galaxies en spirales

photo

Gravure : Micro Usinage Laser.

mire 72 " d'arc

Exemples de sources test

Disque Ø 32 " d'arc

BinaireDisque Ø 0,8" d'arc

source test

Lab prototype: Fresnel array module

C = 8 cm

116 zones (26 680 apertures)

Opaque foil: inox 80 µm thick

Tested in the visible (450-850 nm)

F= 23 m for = 600 nm

Lab prototype, Focal module

Field "lens" Order 0 Mask Chromatic correction+ doublet focalization

Final image

23 m

Lab prototype, focal module, zoom on the corrector lens• 116 zones, 16 mm diameter, Blazed for 600 nm

• Fused silica

• Résolution selon le plan de la lentille de 1nm, hauteur des marches PTV 1.37 µm

• Ion beam etched (SILIOS), 128 levels,

• 1 m "location" precision, 10 nm "depth" precision

Diverging Fresnel lens mounted in the optical train

Qualitative results: images of artificial sources

uniform Disk 32 arc sec

uniform Disk 0.8 arc sec

Galaxy-shaped target 72 arc sec

broad spectral illumination: 550 - 750 nm

uniform Disk 0.8 arc secwith turbulence

double sourcehigh dynamic range

Quantitative results: measured angular resolution

Diffraction limited theoretical profile

Sampled optical point spread function

The prototype is quasi diffraction limited

Quantitative results: dynamic range optically measured versus numerically simulated

8 cm 116 zones

Optical image

8 cm 116 zonesNumerical Fresnel wave propagation

Through all the optical elements

In these saturated images of a point source, the average background is at 2 *10 -6

Luminosity scale

amplified x1000

Luminosity scale

amplified x1000

The numerical Fresnel propagation tool has been developed for testing large arrays

Quantitative results: PSF of a 300 zones Fresnel Imager (720 000 apertures)

QuickTime™ et undécompresseur TIFF (non compressé)

sont requis pour visionner cette image.

Not apodized, no order 0 mask

numerically simulated

Log dynamc range

Quantitative results: PSF of a 300 zones Fresnel Imager (720 000 apertures)

Apodized, order 0 masked

numerically simulated

Log dynamc range

Position in the field (resels)1/4 of the field represented

Log dynamc range

Quantitative results: PSF of a 300 zones Fresnel Imager (720 000 apertures)

Prolate apodized, order 0 masked

Beyond Orthogonality : improving transmission efficiency and dynamic range

directionnal " Spergle" type

Quantitative results: PSFs of non-orthogonal, square aperture imagers

luminosity scale:Power 1/4 to show

background

300 zones,Square aperturecosine apodized, order 0 masked

Quantitative results: Convolution simulations

300 zones, Square aperturecosine apodized, order 0 masked

HH_30BW, raw image (from HST)

HH_30BW, convoluted

The spikes do not degrade extended images

PSF

III. Space missions scenarios

To be proposed for the 2020-2025 period

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Not quite yet

XIXth century, 19 meter long, 76 cm Nice Obs refractor

Generation II prototype: tests on

high dynamic rangesky sources

Generation II prototype: tests on the sky

350 zones,20 cm aperture20 meter focal, 700 mas resolution106 or more dynamic range

To be built and operated 2008-2010, financed by CNES, subject of a present Ph.D. thesis

III. Space missions scenarios

Space Missions scenarios: Formation flying configuration

"lens" and "receptor" vessels for a 10m circular array configuration

Space Missions scenarios: Formation flying configuration

sat 10 à 30K100K

Mat isolent

V-groove

50K

simple pare soleil multi couches

structure type Astromesh

ressorts à forceconstante

difficulté de mise en œuvre (voir JWST)

sat 10 à 30K100K

Mat isolent

V-groove

50K

simple pare soleil multi couches

structure type Astromesh

ressorts à forceconstante

difficulté de mise en œuvre (voir JWST)

Principe des mesures (2x2 d.d.l. + F) :

1) Le « dépointage » du grand axe optique (Zopt) par rapport à la cible ZG est représenté parL. Il

permet d’estimer le déport latéral xL = F. L. Sa

figuration sur le plan focal du SSSL (ci-contre) est représenté par l’écart entre le motif des diodes laser implanté sur la grande lentille et la cible stellaire, caractérisée, en fait, par un « motif stellaire » avec ou sans la cible (cachée par la lentille en « contrôle fin »).

2) Le dépointage de l’axe optique du Récepteur par rapport au grand axe optique (R) est représenté par l’écart angulaire [ ZOR, ZOPT ].

3) Mesure de la distance Focale: En fin de phase d’acquisition, on estimera F à partir de la taille du motif de diodes laser. Par contre, la mesure fine de la focale sera effectuée par télémétrie Laser en phase de contrôle fin.

Space Missions scenarios: Navigation Control Scheme

Plan focal du SSSL dans l’Optique Réceptrice ZG (la

cible)Axe Optique du Récepteur :

ZOR

ZOPT (grand

axe optique)

R

L(= xL/F)

Lentille de Fresnel

Satellite Récepteur

Grand Axe « optique »

Olp

LP

Oor

Zopt

ZOR

R

ZG(étoile)

xL

Satellite Lentille de FresnelZL

P

FL

Schéma de principe de l’instrument distribué

Diode Laser

Space Missions scenarios: key parameters for spacecraft architecture

Orbit and mission- environment- Communications to ground- Vessel to vessel communications

- technology - fabrication- Lissajou orbits

TM/TC 2 par satellite terre/anti-terreLiaison RF sensing (type SimbolX) inter-satellite pour la formation

Moon

40°

SUN

Trajectoire typique montrant qu'au -delà de 100 000 km de la Terre,la MGA pointée comme le GS voit la Terre avec ses 40° d'ouvertur e

Moon

40°

SUN

Trajectoire typique montrant qu'au -delà de 100 000 km de la Terre,la MGA pointée comme le GS voit la Terre avec ses 40° d'ouvertur e

ecliptic plane

sun

small Lissajou

typically: period: 6 months

1 avoidable eclipse every 6 years

acceptable depointing angle of the line of sight = total shield angle protection – Earth, Sun and Moon covering (fonction of the L2 orbit)

sun

ecliptic planeEarth

Moon worst caseevery 28 days

L2

20

0 0

00

km

8°14°

Fresnel lenslight shield

line of sight

TMI Reflector Array (0 à 40°)1 on receptor spacecraft facing earth

fixed RA Antenna & GS Possible a partir de 100 000km from Earth

Space Missions scenarios: focal instrumentation

Intégration of science

and navigation channels:

privileged Scenarios

Space Missions scenarios: focal instrumentationchromatic correction optics

By réfraction By reflection

• NUV+VIS+NIR : lentille de Fresnel blazée à l’ordre –1 qui fonctionne en transmission, suivie d’un doublet convergent et achromatique technologie validée TRL04 : R&T CNES 2004-2007R&T CNES 2004-2007

• UV : miroir de Fresnel blazée à l’ordre –1 ayant double fonction : 1- Réseau correcteur en réflexion et hors axe. 2- Focalisation du faisceau par une concavité globale additionnelle

R&T CNES à venirR&T CNES à venir.

LFCLFC MFCFMFCF

IV. Astrophysical targets

Extra Galactic and Young Universe

Mission Physical Phenomenon Spectral Range (nm)

Dynamic Range within.

5 resels

Angular Resolutions

(mas)

Extra Galactic

lensing

Column density mapping

Black Body, Axion Ray Detection"

2000

500010-4 14 - 34

Extra Galactic

lensingColumn Density mapping, Black Body

600

200010-4 12 - 41

Extra Galactic to Z, Lyman Young Universe, Galaxy formation

1000

200010-4 7 - 14

Extra Galactic to Z, Lyman

breakRe-inonization period of the universe

600

120010-4 12 - 25

Color Code => Spectral Band : IR NIR Vis NUV FUV

Scientific Requirements

Extra Galactic and Young Universe

Mission D(m)

D, Field of View

(m)

Channel

Capture size and Bands

x y

Transfer Ratekbps

Amount captured

Images

Integrated time (h)

Mission Duration

(years)

Extra Galactic

lensing30 2

Pointing M2

2000*2000

3 bands11 4300 10 6,4

Extra Galactic

lensing10 1,2

Pointing M2

/Separation

2000*2000

3 bands11 9262 3 6,3

Extra Galactic at Z, Lyman 30 2

Pointing M2

2000*200010*10*2000

36 3993 20 8,9

Extra Galactic at z, Lyman break 30 2

Pointing M2

2000*200010*10*2000

11 9160 3 6,3

Instrumentation specifications t =3 h : for Changing Object t = 6 h :for Changing Spectral Band

Active Regions in Our Galaxy

Missions Physical Phenomenon Spectral Band (nm)

Dynamic range in 5

resels

Angular Resolution (mas)

Central Galactic Region, Dust and Globular Cluster

Density mass, Central Black hole,

I.R. absorption in interstella

2000

500010-4 14 - 34

Ionized density of Galactic Clouds,

Active Core

“Astrochemistry”

- Extra Galactic core

280

45010-4 6 - 9

Ionized density of Galactic Clouds,

Active Core

Astrochemistry, development of interstellar in Heavy element,

High Energy

120

28010-4 7 - 17

Scientific Requirements

Color Code => Spectral Band : IR NIR Vis NUV FUV Distance Between Objects : 0,2° - 0,5° No of Objects per spectral Band : 20

Active Regions in Our Galaxy

Mission Cgr(m)

D, Field of View

(m)

Channel

Capture size and Bands

x y

Transfer Ratekbps

Amount

captured

Images

Integrated time

(h)

Mission Duration

(years)

Central Galactic Region, Dust and Globular Cluster

30 2 Pointing M2 2000*2000

3 bands11 5192 120 7,7

Ionized density of Galactic

Clouds, Active Core

10 1,2 Pointing M2

/Separation

2000$200010*10*2000

21 6438 10 6,0

Ionized density of Galactic

Clouds, Active Core

3,5 0,6 Pointing M2

2000*200010*10*2000

43 4050 5 5,9

Instruments specifications

IR NIR Vis NUV FUV

Imagery Stellar and Circumstellar

With a 500 m array ?

Imagery Stellar and Circumstellar

Missions Physical Phenomenon Spectral Band (nm)

Dynamic range in 5

resels

Angular Resolution (mas)

Accretion disk, Jets, Photospheres

Evolution of stellar,Mass in Extreme conditions

13010-5

1

Pphotospheres and Circumstellar

Physic stellar 280-45010-5

15 - 29

Photospheres and Circumstellar :

Near objects

Physic stellar,

Circumstellar Clouds250 10-5 5

Photosphere et Circumstellar :

Far objects

Physic stellar,

Circumstellar Clouds250 10-5 2

Scientific Requirements

IR NIR Vis NUV FUV

Mission Cgr(m)

D, Field of View

(m)

Channel

Capture size and Bands

x y

Transfer Ratekbps

Amount captured

Images

Integrated

time (h)

Mission Duration

(years)

Accretion disk, Jets,

Photospheres30 2 none

4000*4000400*400*1000

43 2683 20 7,0

Photospheres, Circumstellar

3,5 0,6

Pointing M2

/Seperation

2000*2000400*400*400

213 19299 1 8,8

Photospheres, Circumstellar :

Near objects10 1,2 none

2000*2000400*400*400

213 23217 1 10,6

Photosphere, Circumstellar :

Far objects30 2 none

4000*4000400*400*1000

85 6191 10 9,2

Instrument Specifications

IR NIR Vis NUV FUV

Imagery stellar et circumstellar

ExoplanetsEarth @ 10 pc detection and spectroscopy

40m array, 300 Fresnel zones, PIAA, spectral resolution 50, 2*48h exposure time

"Exoplanets"

Missions Physical Phenomenon Spectral Band (nm)

Dynamic range

in 5 resels

Angular Resolution

(mas)

Exoplanets joviennes

Planets Systems,

atmospheres

600 -1200 10-8 17 - 25

Exoplanets telluric in IR

Planets Systems,

atmospheres

2000-5000 10-8 40 - 100

Exoplanets joviennes and

telluriques

Planets Systems,

atmospheres

600 -800 10-8 4 - 6

Exoplanets tellurics in IR

Planets Systems,

atmospheres

2000-5000 10-8 14 - 34

Scientific Requirements

IR NIR Vis NUV FUV

Exoplanets

Mission Cgr(m)

D, Field of View

(m)

Channel

Capture size and Bands

x y

Transfer Ratekbps

Amount

captured

Images

Integrated

time (h)

Mission Duration

(years)

Exoplanets 10 1,2 Point at M2

4000*4000300*300*100

71 6500 10 9,6

Exoplanets 10 1,2 Point at M2

4000*4000300*300*100

43 6300 10 9,4

Exoplanets 30 3 Point at M2

4000*4000300*300*100

213 4400 10 6,6

Exoplanets 30 3 Point at M2

4000*4000300*300*100

85 6000 10 9,0

Instruments Specifications

IR NIR Vis NUV FUV

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Bonus slides

Achromatisation principle

Converging lensOperating at order -1