icso 2006 conference on space optics estec, noordwijk, 29/06/2006
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
Multi-aperture Instantaneous Interferometric Imaging of Extended &
Moving Objects by Phase Optimized Spatial Filtering
Luc Damé, Xiyang Fu, Virginie Maury & Christophe MontaronService d'Aéronomie du CNRS & LESIA Meudon Observatory, France
ICSO 2006Conference on Space OpticsESTEC, Noordwijk, 29/06/2006
Lyman 40"x40" – VAULT/NRLSOLARNET/SPI - PROTEUS
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"
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 > /300!
SOLARNET R&D Program: Demonstrate Concept and Performances on a Representative Breadboard
• Cophasing & direct imaging in laboratory in 98–2000 (measured /300 phasing)• 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 /100 this summer; first images next year (filters & SDM 0.1 nm spectral resolution).
SOLARNET Breadboard: more than 150 optics and detectors!
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)
Towards Very High Resolution
An INTERFEROMETER rather than a large telescope:
– Reduced height & mass 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 the "Perfect" Telescope
1.5 m
1 m UV “Telescope”: 0.02"?: 1 m UV Interferometer: 0.02"
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 110–400nm with a subtractive double monochromator FUV & UV, coupled to an IFTS 0.002nm
Schematic of SOLARNET Breadboard
Phase measure
Cophasing in Practice
Recombination (in pupil plane on a 1mmRecombination (in pupil plane on a 1mm22 diode) of the 3 beams diode) of the 3 beamsin 2 of the reference interferometers after spatial filteringin 2 of the reference interferometers after spatial filtering
Delay Line
i
i
Modulation Delay Line
i
Cophasing by Double Synchronous
Detection(global WL phase shift)
• 1f provides the error(zeroing method)
• 2f gives the amplitude
Modulation
Delay Line
Recombining Cubes
Photodiodes
White LightInterferogram
Single FrequencyDemodulation
Double Frequency Demodulation
Extended Source - WL - Spatial Filtering
Photodiode
Entrance optics Diameter: L
∫ ⎥⎦⎤
⎢⎣⎡
⎟⎟⎠⎞
⎜⎜⎝⎛ ⎟⎠
⎞⎜⎝⎛ +−ℜ+∗=
ββδ
πββδ
,..)(2exp1).,().,)(()( ddhjeSffdisqPSFI
T
Filtering HolesDiameter: T
h
4 m
Phase Measure Spatial FilteringWith an extented source
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
1.7%
Selection Hole
Microscopeobjective
Image Filtered image
Visibility Ø5µØ10µØ20µ
FOV Centering and Bias
base 1-2
base 1-3base 2-3
High ContrastFiltered Source 1 2
3
OPD (µm)
Contrast (%)
δ1 δ2 δ3
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Reference FOV and Spatial Filtering
A small decentering of the reference field small)in the baseline direction will produce a bias in the WLF absolute nulling OPD position of δ ~ h. When the intensity distribution is centered (SYMETRY for the 3 baselines), the contrast is maximum on the 3 interferometers and bias is null.
Extreme - highly structured - source in
the reduced FOV after filtering
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1 2
3
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!
1 2
3
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)
Miniaturization of the Reference Interferometers (Phase Measure)
From a breadboard more than a meter long…
… to a 15 centimeters block!
1500 mm
1100
mm
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?)
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)
It is more than appropriate to pursue the effort
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.
Thank you!J.-F. HochedezDavid BerghmansFrédéric CletteSteven Dewitte
Werner CurdtEckart Marsch
Volker Bothmer
Richard Harrison
S. Turck-Chieze
Patrick BoumierTahar Amari
Brigitte SchmiederJ.M. MalherbeGuillaume AulanierPascal Démoulin
Silvano Fineschi
J. Trujillo-Bueno
James KlimchukAngelos Vourlidas
Ted Tarbell
Philippe Lamy
Serge Koutchmy
Eric QuémeraisRosine Lallement
Siraj Hasan
Guoxiang Ai