large dynamic range co- phasing system development for segmented telescope mirrors juan f simar –...
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Large Dynamic Range Co-Phasing System Development
for Segmented Telescope Mirrors
Juan F Simar – ARC Phd StudentCentre Spatial de Liège
Université de Liège
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• Context
• Future Projects
• State of the art
• CSL Proposed Concept
• Activity plan
• Possible applications
• Conclusion
Outlook
3
Context
Maximum On-ground monolithic mirror diameter (space
telescopes diameter are limited by
launcher capacity to 4m)
10m
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Context
Hubble Space Telescope (2.6m) and James Webb Space Telescope (6.5m) Comparison
Segmented mirrors are
folded in ground and
assembled in flight, due to
this, distances between
segments after assemblage
have an order of magnitude
of 100µm
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Context
Tip / Tilt Correction
Piston Correction
Note: Degrees and distance are exaggerated for explanation purpose
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Future Projects
Future Space Telescopes Projects
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State of the art
Spec JWST:
Tip / Tilt range > 0.3 arcsec
Piston range > 100µm
Today technology (JWST)
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CSL Proposed Concept
Coarse phasingRange 100µm (500µm target)
Resolution 300nm (100nm target)
Proposed rangeFine phasing
Range 300nm (400nm target)
Resolution 20nm (10nm target)
(Fine Phasing is under development in the frame of another CSL project)
Interferometric techniques to perform measurements
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CSL Proposed Concept
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*
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synthsynth
synth
P
If λ1 is close to λ2 then λsynth is high and range of piston measure (P) is high
Coarse Phasing with beat technique
Beat techniques (Two waves mixing)
give a synthetic wave several orders of magnitude larger
than single wave components
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CSL Proposed Concept
As a part of Beat method studies, Heterodyne mixing techniques will be assessed in order to reduce the difference between λ1 and λ2 and
increase piston range measurement form 100µm to 500µm
Phase retrieval and phase diversity techniques will be assessed in order to be implemented as
coarse method sensing using Beat method
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Activity planFormation
Real Timealgorithm
implementation
Prototypingcoarse sensor
(open loop)Fine Phasing sensormonochromatic Φr
(open loop)
Φr = Phase retrieval
Φd = Phase diversity
Coarse phasing
Stacking fine and
coarse (open loop)
Measure method assessmentΦr, Φd + Beat ?
(another method can be implemented)
Close loop
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Possible applicationsBigger space telescopes
JWST (6.5m,year 2014)
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Possible applicationsEasy to launch space telescopes
(small segments)
JWST (6.5m,year 2014)
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Conclusion
-Co-phasing systems is a key factor in future space and earth observation missions
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