1. Large Dynamic Range Co- Phasing System Development for Segmented Telescope Mirrors Juan F Simar – ARC Phd Student Centre Spatial de Liège Université de Liège

2. 2 Context Future Projects State of the art CSL Proposed Concept Activity plan Possible applications Conclusion Outlook

3. 3 Context Maximum On-ground monolithic mirror diameter (space telescopes diameter are limited by launcher capacity to 4m) 10m

4. 4 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

5. 5 Context Tip / Tilt Correction Piston Correction Note: Degrees and distance are exaggerated for explanation purpose

6. 6 Future Projects Future Space Telescopes Projects

7. 7 State of the art Spec JWST: Tip / Tilt range > 0.3 arcsec Piston range > 100µm Today technology (JWST)

8. 8 CSL Proposed Concept Coarse phasing Range 100µm (500µm target) Resolution 300nm (100nm target) Proposed range Fine 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

9. 9 CSL Proposed Concept If λ 1 is close to λ 2 then λ synth 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

10. 10 CSL Proposed Concept As a part of Beat method studies, Heterodyne mixing techniques will be assessed in order to reduce the difference between λ 1 and λ 2 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

11. 11 Activity plan Formation Real Time algorithm implementation Prototyping coarse sensor (open loop) Fine Phasing sensor monochromatic Φr (open loop) Φr = Phase retrieval Φd = Phase diversity Coarse phasing Stacking fine and coarse (open loop) Measure method assessment Φr, Φd + Beat ? (another method can be implemented) Close loop

12. 12 Possible applications Bigger space telescopes JWST (6.5m,year 2014)

13. 13 Possible applications Easy to launch space telescopes (small segments) JWST (6.5m,year 2014)

14. 14 Conclusion -Co-phasing systems is a key factor in future space and earth observation missions