slides at NUVA meeting El Escorial Spain 2007

The Fresnel Diffractive Imager project
--Principles, Instrumentation and Mission scenarios
Université
de Toulouse,
CNRS
France
Laurent Koechlin,
Denis Serre,
Paul Deba,
Truswin Raksasataya,
Christelle Peillon,
Emmanuel Hinglais,
Paul Duchon,
Pierre Etcheto,
Christian Dupuy,
Benoît Meyssignac,
Laurent Doumic.
The Fresnel Diffractive Imager project
I. Optical Principles
Focalization by diffraction
Chromatic correction
High dynamic range
II. Lab prototype, optical and numerical tests
Optical setup
Tests results on artificial sources
Tests planned on sky sources
Numerical simulations for large arrays
III. Space mission scenarios
Orbits and Formation flying configuration
Primary array vessel design
Focal instrumentation design
IV. Astrophysical targets
Some of the possible scenarios
I. Optical Principles
Focalization : different ways
Lens
focus
Plane wavefront
Lens (or miror): focusing by refraction (or reflexion)
Fresnel array: focusing by diffraction …
Order 1 :
convergent
Order 0 :
plane
wave
focus
2D radial expansion
Concentric geometry (Soret 1875)
Efficiency at order 1: 10%
Exemple for
15 Fresnel zones
2D Cartesian expansion
Orthogonal geometry (2005)
Efficiency at order 1: 4 to 8 %
Exemple for
30 Fresnel zones
g(x)= 1 si (x2 +f2)1/2 
[(f/ml + (k-off) +1/2) ml ; (f/ml + (k-off) +1) ml[
Fresnel Zone plate or
Aperture synthesis array ?
(here: 1740 ouvertures)
sinon g(x) = 0
Transmission (x, y) = g (x)
xor
g (y)
Image formation
circular geometry => isotropic PSF
Image
Aperture
non linear luminosity scale
In order to show the faint
isotropic rings.
Image formation
Orthogonal geometry => orthogonal PSF
Image
Aperture
Quasi no
stray light
except in
the spikes.
Transmission:
g(x)  g(y)
non linear luminosity scale
In order to show the faint
spikes.
Image formation
Case of a second source in the field:
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
Images of a point source by:
150 Fresnel
zones
luminosity scale:
Power 1/4 to show spikes
1500 Fresnel zones
Solid square aperture
"for" Fresnel Arrays:
No mirror, no lens to focalize : just vacuum and opaque material.
=> a potentially very broad operational domain: 90nm - 25 mm
Angular resolution: as high as with a mirror the size of the whole array.
High dynamic range: 108 on compact objects for a 300 zones array
Large tolerance in positioning of subapertures for l/20 wavefront quality:
100 mm in the plane of the array
10 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.
"against" Fresnel Arrays:
C
F = C2/8N l
Chromaticity... corrected by small diffractive lens after focus,
(order 1 chromaticity cancelled by order -1 chromaticity),
but bandpass limitations remain: Dl/l = √2 S/C
kilometric focal lengths => requires formation flying in space
Low transmission compared to a mirror :
t = 5 to 10%
Optical scheme of the Fresnel Diffractive Imager
Primary Fresnel array
e.g. 20 m
Diffractive lens
at order -1
e.g. 10 cm
Field Optics
10 to 100 km e.g. 2m
Converging lens
e.g. 10 cm
mask
Order 0 rays
Focal
Instrumentation
image plane 1
dispersed
Img. plane 2 :
achromatic
pupil plane
Order 1 rays, focused
by primary array
Spacecraft 1
holding primary Fresnel array
Spacecraft 2 holding focal instrumentation
The field - bandpas compromise
Chromatically
aberrated beam
at prime focus
Field delimited
by field mirror
The chromatic
corrector
does 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 Toulouse
2006 - 2008
Lab Prototype: light source module
• Étoiles doubles
photo
source test
• Galaxies en spirales
photo
Exemples de sources
test
Disque
Ø 0,8"
d'arc
Binaire
Disque
Ø 32 " d'arc
Gravure : Micro Usinage Laser.
mire 72 "
d'arc
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 l= 600 nm
Lab prototype, Focal module
Field "lens"
23 m
Order 0 Mask
Chromatic correction
+ doublet focalization
Final image
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 mm "location" precision, 10 nm "depth" precision
Diverging Fresnel lens mounted in the optical train
Qualitative results: images of artificial sources
broad spectral illumination: 550 - 750 nm
uniform Disk 0.8 arc sec
uniform Disk 0.8 arc sec
with turbulence
uniform Disk 32 arc sec
double source
high dynamic range
Galaxy-shaped target
72 arc sec
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
In these saturated images of a point source, the average background is at 2 *10 -6
Luminosity scale
amplified x1000
8 cm 116 zones
Optical image
Luminosity scale
amplified x1000
8 cm 116 zones
Numerical Fresnel wave propagation
Through all the optical elements
The numerical Fresnel propagation tool has been developed for testing large arrays
Quantitative results: PSF of a 300 zones Fresnel Imager
(720 000 apertures)
numerically
simulated
Log dynamc
range
QuickTime™ et un
décompresseur TIFF (non compressé)
sont requis pour visionner cette image.
Not apodized,
no order 0 mask
Quantitative results:
PSF of a 300 zones Fresnel Imager (720 000 apertures)
numerically
simulated
Log dynamc
range
Apodized,
order 0 masked
Quantitative results:
PSF of a 300 zones Fresnel Imager (720 000 apertures)
Prolate apodized,
order 0 masked
Log dynamc
range
Position in the field (resels)
1/4 of the field represented
Beyond Orthogonality :
improving transmission efficiency and dynamic range
directionnal " Spergle" type
Quantitative results: PSFs of non-orthogonal, square
aperture imagers
300 zones,
Square aperture
cosine apodized,
order 0 masked
luminosity scale:
Power 1/4 to show background
Quantitative results: Convolution simulations
300 zones, Square aperture
cosine apodized, order 0 masked
The spikes do not degrade extended images
PSF
HH_30BW, raw image
(from HST)
HH_30BW, convoluted
III. Space missions scenarios
To be proposed for the 2020-2025 period
Generation II prototype:
tests on
high dynamic range
sky sources
Not quite yet
QuickTime™ et un
décompresseur TIFF (non compressé)
sont requis pour visionner cette image.
XIXth century, 19 meter long, 76 cm Nice Obs refractor
Generation II prototype: tests on the sky
350 zones,
20 cm aperture
20 meter focal,
700 mas resolution
106 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
simple pare soleil multi couches
Mat isolent
structure type Astromesh
ressorts à force
constante
100K
10 à 30K
sat
50K
V-groove
difficulté de mise en œuvre (voir JWST)
Space Missions scenarios: Navigation Control Scheme
Principe des mesures (2x2 d.d.l. + F) :
1) Le « dépointage » du grand axe optique (Zopt)
par rapport à la cible ZG est représenté par DqL. Il
permet d’estimer le déport latéral DxL = F. DqL. 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 (DqR) est représenté
par l’écart angulaire
Olp[ ZOR, ZOPT ]. ZOR Oor
ZG(étoile)
F
DqL
Zopt
DqL
P
ZL
P
Grand Axe
« optique »
Plan focal du SSSL dans l’Optique
Réceptrice
ZG (la
Axe Optique
du Récepteur :
cible)
ZOR
DqL(= DxL/F)
DqR
Lentille de
Fresnel
Diode Laser
Dq
R
Dx
L
Satellite
Satellite Lentille de
Récepteur
Fresnel Schéma de principe de l’instrument
distribué
ZOPT (grand
axe optique)
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: key parameters for
spacecraft architecture
Orbit and mission
- environment
- Communications to ground
- Vessel to vessel communications
- technology
- fabrication
- Lissajou orbits
Moon
40°
SUN
small Lissajou
sun
period: 6 months
line of sight
1 avoidable eclipse every 6 years
Fresnel lens
Trajectoire typique montrant qu'au-delà de 100 000 km de la Terre,
light shield
sun
ecliptic plane
acceptable depointing angle of the line of
sight
= total shield angle protection – Earth, Sun
and Moon covering
(fonction of the L2
orbit)
Earth
L2
Moon worst case
every 28 days
TMI Reflector Array (0 à 40°)
1 on receptor spacecraft facing earth
200 000 km
typically:
la MGA pointée comme le GS voit la Terre avec ses 40° d'ouverture
fixed RA Antenna & GS
Possible a partir de
100 000km from Earth
TM/TC 2 par satellite terre/antiterre
Liaison RF sensing
(type SimbolX)
inter-satellite pour la formation
Space Missions scenarios: focal instrumentation
Intégration of science
and navigation channels:
privileged Scenarios
Space Missions scenarios: focal instrumentation
chromatic correction optics
LFC
By réfraction
By reflection
MFCF
•
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 2004-2007
•
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 venir.
IV. Astrophysical targets
Extra Galactic and Young Universe
Scientific Requirements
Mission
Physical Phenomenon
Spectral
Range (nm)
Dynamic
Range
within.
Angular
Resolutions
(mas)
5 resels
Extra Galactic
lensing
Column density mapping
Black Body, Axion Ray Detection"
2000
5000
10-4
14 - 34
Extra Galactic
lensing
Column Density mapping, Black Body
600
2000
10-4
12 - 41
Extra Galactic
to Z, Lyman a
Young Universe, Galaxy formation
1000
2000
10-4
7 - 14
Extra Galactic
to Z, Lyman
break
Re-inonization period of the universe
600
1200
10-4
12 - 25
Color Code => Spectral Band : IR NIR Vis NUV FUV
Extra Galactic and Young Universe
Instrumentation specifications
t =3 h : for Changing Object
Mission
D
(m)
Extra Galactic
lensing
30
D,
Field of
View
(m)
t = 6 h :for Changing Spectral Band
Channel
Capture size
and Bands
xy
l
Transfer
Rate
kbps
Amount Integr Mission
captured ated Duration
Images
time
(h)
(years)
2
Pointing
M2
2000*2000
3 bands
11
4300
10
6,4
2000*2000
3 bands
11
9262
3
6,3
36
3993
20
8,9
11
9160
3
6,3
Extra Galactic
lensing
10
1,2
Pointing
M2
/Separati
on
Extra Galactic at
Z, Lyman a
30
2
Pointing
M2
2000*2000
Extra Galactic at
z, Lyman break
30
2
Pointing
M2
2000*2000
10*10*2000
10*10*2000
Active Regions in Our Galaxy
Scientific Requirements
Missions
Physical Phenomenon
Spectral
Band
Dynamic
range in 5
(nm)
resels
Angular
Resoluti
on (mas)
Central Galactic
Region, Dust and
Globular Cluster
Density mass, Central Black hole,
I.R. absorption in interstella
2000
5000
10-4
14 - 34
Ionized density of
Galactic Clouds,
Active Core
“Astrochemistry”
- Extra Galactic core
280
450
10-4
6-9
Ionized density of
Galactic Clouds,
Active Core
Astrochemistry, development of
interstellar in Heavy element,
High Energy
120
280
10-4
7 - 17
Distance Between Objects : 0,2° - 0,5°
No of Objects per spectral Band : 20
Color Code => Spectral Band : IR NIR Vis NUV FUV
Active Regions in Our Galaxy
Instruments specifications
Mission
Cgr
(m)
D,
Field of
View
(m)
2
Channel
Capture
size and
Bands
Transfe
r Rate
kbps
xy
l
Pointing M2 2000*2000
Central Galactic
Region, Dust and
Globular Cluster
30
Ionized density
of Galactic
Clouds, Active
Core
10
1,2
Pointing
M2
/Separatio
n
2000$2000
Ionized density
of Galactic
Clouds, Active
Core
3,5
0,6
Pointing
M2
2000*2000
Amoun Integrat Mission
ed time Duration
t
(h)
(years)
capture
d
Images
11
5192
120
7,7
21
6438
10
6,0
43
4050
5
5,9
3 bands
IR NIR Vis NUV FUV
10*10*2000
10*10*2000
Imagery Stellar and Circumstellar
With a 500 m array ?
Imagery Stellar and Circumstellar
Scientific Requirements
Missions
Accretion disk, Jets,
Photospheres
Physical Phenomenon
Evolution of stellar,
Mass in Extreme conditions
Spectral
Band (nm)
130
Dynamic
range in 5
resels
10-5
10-5
Angular
Resoluti
on (mas)
1
Pphotospheres and
Circumstellar
Physic stellar
280-450
Photospheres and
Circumstellar :
Near objects
Physic stellar,
Circumstellar Clouds
250
10-5
5
Photosphere et
Circumstellar :
Far objects
Physic stellar,
Circumstellar Clouds
250
10-5
2
IR NIR Vis NUV FUV
15 - 29
Imagery stellar et circumstellar
Instrument Specifications
Mission
Cgr
(m)
Accretion disk,
Jets,
Photospheres
30
D, Field
of View
(m)
Channel
2
none
Capture size
and Bands
xy
l
Photospheres,
Circumstellar
3,5
0,6
Pointing
M2
/Seperati
on
Photospheres,
Circumstellar :
Near objects
10
1,2
none
Photosphere,
Circumstellar :
Far objects
30
2
none
IR NIR Vis NUV FUV
4000*4000
400*400*1000
2000*2000
400*400*400
2000*2000
400*400*400
4000*4000
400*400*1000
Transfer
Rate
kbps
Amount Integra Mission
ted
Duration
captured
Images
time
43
2683
20
7,0
213
19299
1
8,8
213
23217
1
10,6
85
6191
10
9,2
(h)
(years)
Exoplanets
Earth @ 10 pc detection and spectroscopy
40m array, 300 Fresnel zones, PIAA, spectral resolution 50, 2*48h
"Exoplanets"
Scientific Requirements
Missions
Physical Phenomenon
Spectral Band
(nm)
Dynam
ic 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
IR NIR Vis NUV FUV
Exoplanets
Instruments Specifications
Mission
Cgr
(m)
D, Field of
View
(m)
Channel
Capture size
and Bands
xy
l
Transfer
Rate
kbps
Amou Integra Mission
ted
Duration
nt
(years)
captur time
(h)
ed
Images
Exoplanets
Exoplanets
Exoplanets
Exoplanets
10
10
30
30
1,2
1,2
3
3
Point at
M2
4000*4000
Point at
M2
4000*4000
Point at
M2
4000*4000
Point at
M2
4000*4000
71
6500
10
9,6
43
6300
10
9,4
213
4400
10
6,6
85
6000
10
9,0
300*300*100
300*300*100
300*300*100
300*300*100
IR NIR Vis NUV FUV
¡Muchas gracias por su atencion!
Bonus slides
Achromatisation principle
Converging lens
Operating at order -1