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ICSO 2006 Conference on Space Optics ESTEC, Noordwijk, 29/06/2006

Multi-aperture Instantaneous Interferometric Imaging of Extended & Moving Objects by Phase Optimized Spatial Filtering Luc Damé, Xiyang Fu, Virginie Maury & Christophe Montaron Service d'Aéronomie du CNRS & LESIA Meudon Observatory, France.

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ICSO 2006 Conference on Space Optics ESTEC, Noordwijk, 29/06/2006

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  1. Multi-aperture Instantaneous Interferometric Imaging of Extended & Moving Objects by Phase Optimized Spatial FilteringLuc Damé, Xiyang Fu, Virginie Maury & Christophe MontaronService d'Aéronomie du CNRS & LESIA Meudon Observatory, France ICSO 2006Conference on Space OpticsESTEC, Noordwijk, 29/06/2006 SOLARNET/SPI - PROTEUS Lyman  40"x40" – VAULT/NRL

  2. Context – a Short History • Solar interferometry, DIRECT IMAGING OF AN EXTENDED FIELD OF VIEW in the FUV was first proposed in 1986, 20 years ago, on the EURECA platform! (on ground: ASSI table) • It was then proposed in 1989 for ESA/M2 and was selected for a Phase A on the Space Station (SIMURIS Mission with the Solar Ultraviolet Network, SUN, a 4-telescope non-redundant 2 m baseline array in rotation on the IPS) • 93: ESA/M3 as MUST/SIMURIS, a 5-telescope circular configuration and, in parallel, was studied for adaptation on the Space Station using an Hexapod support structure • In 2000, SOLARNET/SPI was proposed for ESA/F2-F3 and recommended by ESTEC review. Even if overcost, the Solar Orbiter was preferred for "political redistribution reasons"

  3. R&D Laboratory Experiments since 1990 on Extended FOV Cophasing and Imaging • Direct cophasing at /300 of two telescopes on an extended laboratory source in 94 • Fringes and cophasing at /140 on the Sun and /220 on stars and Planets (Jupiter, Mars) in 95 and 96 (Obs. Meudon) • Stabilities up to /1000 on solar like flux and /100 on mag. 10 stars (ESA/OAST 2 - 1997) • 2000: acquisition, control and imaging with a 3-telescope cophased breadboard (laboratory setup) with measured stabilities > l/300!

  4. SOLARNET R&D Program: Demonstrate Concept and Performances on a Representative Breadboard • Cophasing & direct imaging in laboratory in 98–2000 (measured l/300phasing) • Adaptation to direct solar observations at Meudon Observatory (Grand Sidérostat de Foucault) in 2001–2002; completion of guiding and fine pointing this spring (0.1"); cophasing l/100this summer; first images next year (filters & SDM 0.1 nm spectral resolution). SOLARNET Breadboard: more than 150 optics and detectors!

  5. Big Issues & Next Steps • R&D • Demonstrate cophased imaging directly on the Sun • Optimize Space Qualification of Fringe Sensor • Complete integration of Focal Instrument • Programme • Prepare ESA Cosmic Vision Response (AO expected end of September)

  6. 1.5 m Towards Very High Resolution 1 m UV Interferometer: 0.02" 1 m UV “Telescope”: 0.02"?: An INTERFEROMETER rather than a large telescope: • Reduced height & mass ê small platform &launcher • Fine Pointing and thermal aspects simplified by small telescopes (use of SiC) • No need for the complex control of a large primary • Phasing and pointing ê the "Perfect" Telescope

  7. SOLARNET is a Unique Concept of Direct Interferometric Imaging on Extended FOV • Compact Configuration: 3 telescopes of Ø350mm on 1m • Spatial Resolution of 0.025” (20–30km on the Sun in the UV) • Multi-wavelengths spectral imaging l110–400nm with a subtractive double monochromator FUV & UV, coupled to an IFTS 0.002nm

  8. Schematic of SOLARNET Breadboard Phase measure

  9. Cophasing in Practice Modulation Delay Line Delay Line i i i Recombination (in pupil plane on a 1mm2 diode) of the 3 beamsin 2 of the reference interferometers after spatial filtering

  10. Recombining Cubes Modulation Delay Line Photodiodes Cophasing by Double Synchronous Detection(global WL phase shift) • 1f provides the error(zeroing method) • 2f gives the amplitude White LightInterferogram Single FrequencyDemodulation Double Frequency Demodulation

  11. 4 m Extended Source - WL - Spatial Filtering h Photodiode Filtering HolesDiameter: FT Entrance optics Diameter: FL

  12. Phase Measure  Spatial Filtering With an extented source Ø a spatial filtering is required to measure a proper contrast Simulation of the interference figure in the case of a contrasted image (granulation – not WL) Principle of a Spatial Filtering Selection Hole Filtered image Image Microscopeobjective Ø5µ Ø10µ Ø20µ Visibility 1.7%

  13. 3 base 1-3 base 2-3 1 2 base 1-2 Contrast (%) OPD (µm) 1 3 2 FOV Centering and Bias High Contrast Filtered Source

  14. 3 1 2 Reference FOV and Spatial Filtering Extreme - highly structured - source in the reduced FOV after filtering A small decentering of the reference field a (a small)in the baseline direction will produce a bias in the WLF absolute nulling OPD position of d ~ ha.When the intensity distribution is centered (SYMETRY for the 3 baselines), the contrast ismaximum on the 3 interferometers and bias is null.

  15. 3 1 2 Automatic Bias Servo • Decentering of the intensity centroïd (barycenter) of the reference field of view creates in each of the three reference interferometers a "bias" compared to zero OPD. • The two major delay lines "monitor" the phase error for B12 and B13 compared to T1  corrections and ∂12 and ∂13 available • The 3d measurement provides the "differential bias" between T2 and T3; it indicates the vertical offset pointing correction • The 2f demodulations of B21, B31 and B32 give the amplitudes; they lower with a bias; the closure error (instrumental) gives the residual horizontal correction (since vertical addressed) • Initial centering and gains are set by initial synchronous demodulation phase measure by jiggling the three active mirrors This is a multiple servo-control system as we love them!

  16. Permanent Implementation • If the jitter is implemented on the entrance hole of the spatial filtering (e.g. at 1 KHz) by the focusing objective, the demodulation of the field centering effect (if any) can be very fast and permanent • Shortage of CNES R&D funds this year (up to now) did not allow to test the method (require object masks, improvement of the 3d interferometer electronics and 2 other synchronous detections) • We are confident on the approach, useful and fast for Earth Observation (but probably unnecessary on the Sun: reduced contrast and structuration in WL)

  17. Miniaturization of the Reference Interferometers (Phase Measure) From a breadboard more than a meter long… 1100 mm 1500 mm … to a 15 centimeters block!

  18. The Interferometric Binding Block of3 Reference Interferometers • It has been designed and realized • Molecular binding • 15 Homosil prisms to sub-µm & sub-arcsec precision • Invar support designed (IDEAS modeling: 0.8 MPA and 2" for ± 5° tolerance) and awaiting realization (test this autumn?)

  19. It is more than appropriate to pursue the effort R&D Status • R&D is necessary prior to accepted project to validate hard points and consolidate mission profile so as to prepare competitive response with SCIENTIFIC and TECHNICAL original content • We have more than 20 years of experience with fringes stabili-zation by synchronous detection (simple and double and, now, with controlled optimization of selective spatial filtering) - and, among them, 10 on the phasing for true imaging on a large FOV • We have developed an optimum technique to phase multiple telescopes on the SAME extended FOV, even is contrasted and mobile (scanned)

  20. Conclusions & Perspectives • We have demonstrated 3-telescope cophasing and imaging in laboratory and we expect to extend the demonstration to the Sun this summer • Both acquisition and tracking are monitored by our method, and the three levels of servo-control are smoothly interacting: guiding of Siderostat (Platform), fine pointing and optimized cophasing on a self referenced external extended source • Extension to Earth Observation (LEO or GEO) is straightforward since acquisition and tracking on an Extended source in White Light are similar to the Solar case. Further, a 5 x Ø2 m circular configuration would fit an Ariane V… This Very High Resolution Interferometry Mission would be possible NOW for a launch in 2012 (as a CNES minisatellite) for the next solar maximum or in 2016 (Cosmic Vision Proposal) in complement or replacement of SO. EU, US, Indian and Chinese contributions are discussed.

  21. Thank you! J.-F. Hochedez David Berghmans Frédéric Clette Steven Dewitte Werner Curdt Eckart Marsch Volker Bothmer Richard Harrison Philippe Lamy Serge Koutchmy Eric Quémerais Rosine Lallement Siraj Hasan Guoxiang Ai S. Turck-Chieze Patrick Boumier Tahar Amari Brigitte Schmieder J.M. Malherbe Guillaume Aulanier Pascal Démoulin Silvano Fineschi J. Trujillo-Bueno James Klimchuk Angelos Vourlidas Ted Tarbell

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