Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Laurent Koechlin Laboratoire d'astrophysique de Toulouse Tarbes, Université de Toulouse CNRS A quick review of tesbed imagers

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Tesbed imagers Research on these testbeds is financed by

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, x2 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 NiceSeptember 23-25, Testbed Gen I ( ): 8x8 cm array 116 zones, 8 x 8 cm apertures "orthocircular" design. F= 23 m at = 600 nm Precision: 5  m on holes positioning => /70 on wavefront. Achievements: Diffraction limited Broad band imaging ( nm) dynamic range Photo T.Raksasataya metal foil 100  m thick Will be presented by Denis Serre

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Testbed Gen II: 20x20 cm, on sky sources ( ) Photo D.Serre 0.8" resolution1000x1000 fieldλ 0 = 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 NiceSeptember 23-25, Metal foil apertures, Slightly apodized, 696 Fresnel zones. 20 cm Photo P.Deba

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Testbed Gen II First light on a star done July 17th Not yet the nominal optics Results & targets will be presented by Truswin Raksasataya

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Goals and first results of testbed Gen II Assess performances on real sky objects: do better than other 20 cm aperture instruments. Targets: Dynamic range on real stars Limiting magnitude Will be presented by Truswin Raksasataya

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Assessment of a membrane telescope is currently envisioned by ESA

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Space mission proposal Science cases? Credibility? 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.

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, 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 NiceSeptember 23-25, The Fresnel Imager Space Mission Field optics telescope 1/10 th to 1/20 th the diameter of Primary Array. Dispersion correction: order -1 diffraction Blazed lens or concave grating, 10 to 30 cm diameter focal Instrumentation: Spectro-imagers Thin membrane "Primary Array" module: 3m to 100m diameter, or more.

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Strategy, sky targets - Start with UV domain? - The UV universe is almost unknown at these resolution and dynamic range - limited budget => limited aperture, but high resolution - High quality wavefront at any wavelength - angular resolution : 7 mas with a 4m Fresnel array

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Space Mission: optical scheme Focal instruments 5 km (for a 4m aperture) to 100 km (for a 30m aperture) image plane 2 achromatic pupil plane Spacecraft 1 Spacecraft 2 image plane 1 dispersed Diffraction order 1: focused, but with chromatic aberration. Diffraction order 0: unfocussed will be focused by field optics, then blocked. Field optics telescope Chromatic correction: Blazed Fresnel grating Large "Primary Fresnel Array: Thin foil, 4 to 30 m diameter, or more. Order zero blocked Solar Baffle, to protect from sunlight Focal instrum.

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Goals and conception of testbed Gen III: UV domain Will be presented by Paul Deba 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.

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Testbed Gen III: UV domain Size : 8 cm, square 240 Fresnel zones ( apertures) metal sheet 100  m thick, laser carved Operates in the UV ( nm) Focal length: 26.6 m for = 250 nm Precision on array : 5  m i.e. /30 on wavefront R&T financed by CNES & STAE Will be presented by Paul Deba

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Targets: S/N on exoplanets in UV Signal / noise as a function of 1 Jupiter diameter planet 0.5 Jupiter diameter Images & spectra of exoplanets: 1 UA from solar type star, 10 Pc away Signal / noise < 3 Signal / noise > 3 Signal / noise > 30 Signal / noise < 3 Signal / noise > 3 4m aperture, 10h integration spectral res.    = 50 dynamic range of raw image: 2 10^-8 uv

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Conclusion: Future space mission. Science cases: Exoplanets stellar physics compact objects reflection nebulae extragalactic solar system objects observation of the earth Build up a proposal for a 2020 / 2025 launch

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25, Thank you for your attention!

Optical principles of diffraction focussing, Preparing the way to space borne Fresnel imagers NiceSeptember 23-25,