Download L`imageur de Fresnel - Laboratoire Astrophysique de Toulouse

A quick review of tesbed
imagers
Laurent Koechlin
Laboratoire d'astrophysique de Toulouse Tarbes,
Université de Toulouse CNRS
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Tesbed imagers
Research on these testbeds is financed by
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
2x2 cm
array
I have it here,
It's working.
live demo
For those who
Haven't already
Seen it…
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Testbed Gen I (2005-2009): 8x8 cm array
Will be presented by Denis Serre
116 zones, 8 x 8 cm
26680 apertures
"orthocircular" design.
F= 23 m at = 600 nm
Precision: 5m on holes positioning
=> /70 on wavefront.
metal foil 100 m thick
Achievements:
Diffraction limited
Broad band imaging (450-850nm)
10-6 dynamic range
Photo T.Raksasataya
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Testbed Gen II: 20x20 cm, on sky sources (2009-2011)
0.8" resolution
1000x1000 field
λ0 = 800 nm
Δλ = 100 nm
Implementation of
testbed Gen II
at Nice observatory
will be presented by
Jean-Pierre Rivet
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
Photo
September
23-25,D.Serre
2009
Metal foil
9.7 105 apertures,
Slightly apodized,
696 Fresnel zones.
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
Photo
September
23-25,P.Deba
2009
Testbed Gen II
Results & targets will be presented by Truswin Raksasataya
First light on a star
done July 17th
Not yet the nominal optics
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Goals and first results of testbed Gen II
Will be presented by Truswin Raksasataya
Assess performances on real sky objects:
do better than other 20 cm aperture instruments.
Targets:
Dynamic range on real stars
Limiting magnitude
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Assessment of a membrane telescope
is currently envisioned by ESA
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Space mission proposal
We have a concept that opens the way to very large apertures in space.
It can be validated on ground based facilities only for small apertures.
Large apertures need to be tested in space,
but it's hard to get a large mission approved if it's based on a new technology.
Science cases?
Credibility?
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Rationale
Meet acceptability threshold for a new technology mission
Make it simple, try to keep the cost below 300 M€
Scientific return over cost:
must be higher than that of competing concepts
λ/50 wavefront, at any λ => High Dynamic range from IR to UV
mas angular resolution
1000x1000 resel. fields
Spectral resolution
Suitable for several astrophysical fields...
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
The Fresnel Imager Space Mission
3m to 100m diameter, or more.
Thin membrane "Primary Array" module:
Field optics telescope
1/10th to 1/20th the diameter
of Primary Array.
Dispersion correction: order -1 diffraction
Blazed lens or concave grating,
10 to 30 cm diameter
focal Instrumentation:
Spectro-imagers
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Strategy, sky targets
- Start with UV domain?
- limited budget => limited aperture, but high resolution
- High quality wavefront at any wavelength
- angular resolution : 7 mas with a 4m Fresnel array
- The UV universe is almost unknown
at these resolution and dynamic range
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Space Mission: optical scheme
Spacecraft
1
Solar Baffle, to
protect from sunlight
Large "Primary Fresnel Array:
Thin foil,
4 to 30 m diameter, or more.
Field optics
telescope
Diffraction order 1: focused,
but with chromatic aberration.
Order zero
blocked
Focal
instrum.
Spacecraft 2
pupil plane
Diffraction order 0: unfocussed
will be focused by field optics, then blocked.
Focal
instruments
Chromatic
correction:
Blazed
Fresnel grating
5 km (for a 4m aperture)
to 100 km (for a 30m aperture)
image plane 1
dispersed
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
image plane 2
achromatic
Nice
September 23-25, 2009
Goals and conception of testbed Gen III: UV domain
Before proposing a UV space mission,
we need to validate the technology in the UV.
Build a testbed to validate :
- the dynamic range,
- wavefront quality,
- angular resolution,
- spectral bandwidth,
- light transmission efficiency.
Will be presented by Paul Deba
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Testbed Gen III: UV domain
Will be presented by Paul Deba
R&T financed by CNES & STAE
Size : 8 cm, square
240 Fresnel zones
(110 000 apertures)
metal sheet 100 m thick, laser
carved
Operates in the UV (250-350 nm)
Focal length: 26.6 m for = 250 nm
Precision on array : 5m
i.e. /30 on wavefront
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Targets: S/N on exoplanets in UV
Signal / noise as a function of 
uv
uv
Signal / noise > 30
1 Jupiter diameter planet
0.5 Jupiter diameter
Signal / noise > 3
Signal / noise > 3
Signal / noise < 3
Signal / noise < 3
Images & spectra of exoplanets:
1 UA from solar type star, 10 Pc away
4m aperture, 10h integration
spectral res.  / = 50
dynamic range of raw image: 2 10^-8
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Conclusion: Future space mission.
Build up a proposal for a 2020 / 2025 launch
Science cases:
Exoplanets
stellar physics
compact objects
reflection nebulae
extragalactic
solar system objects
observation of the earth
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Thank you for your attention!
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009
Optical principles of diffraction focussing,
Preparing the way to space borne Fresnel imagers
Nice
September 23-25, 2009