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OWL Copenhagen, July 2004

OWL Copenhagen, July 2004. A 100-m class optical & near-infrared telescope for the next decade. Feasibility – progress of technology. Reosc, St Pierre du Perray, 1999. Glass-making Slowly evolving technology Extrapolation from 5-m required active optics ! Not easily scalable.

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OWL Copenhagen, July 2004

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  1. OWL Copenhagen, July 2004 A 100-m class optical & near-infrared telescope for the next decade

  2. Feasibility – progress of technology Reosc, St Pierre du Perray, 1999 Glass-making • Slowly evolving technology • Extrapolation from 5-m required active optics ! • Not easily scalable Segmentation Corning, N.Y., 1936 Optical figuring • Metrology-dependent • Rapid evolution • Scalable (somewhat) Segmentation 8-m dia., 8.5 nm RMS Wavefront control • In-situ control of performance • Dealing with inevitable error sources • Tolerances relaxation • Scalable Active optics Schott, Mainz, 1992

  3. VLT (Subaru, Gemini) Active optics Keck Optical segmentation Adaptive optics Hobby-Eberly Low-cost structures / optics

  4. Optical design Adaptive, conjugated to pupil; First generation Adaptive, conjugated to 8km; Second generation

  5. Azimuth tracks Sliding enclosure M2 Handling tool M1 Covers Maintenance facility

  6. Altitude tracks Altitude bearing Azimuth structure & bogies

  7. Corrector & instrumentation Structure ribs (6-fold symmetry) Altitude cradles & bogies

  8. Self-similar fractal mechanical design (with all dimensions as multiple of segment size) • Low production, transport, integration & maintenance cost • Optimal loads transfer to foundations • Low thermal inertia • Low mass (14,800 tons …) • High stiffness (2.6 Hz)

  9. Controlled opto-mechanical system Pre-setting bring optical system into linear regimeMetrology: internal, tolerances ~ 1-2 mm, ~5 arc secsCorrection: re-position Corrector, M3 / M4 / M5 Segments phasing keep M1 and M2 phased within tolerancesMetrology: Edge sensors, Phasing WFSCorrection: Segments actuators Field Stabilization cancel “fast” image motionMetrology: Guide probe Correction: M6 tip-tilt (flat, exit pupil, 2.35-m) Active optics finish off alignment / collimation relax tolerances, control performance & prescriptionMetrology: Wavefront sensor(s)Correction: Rotation & piston M5; M3 & M4 active deformations Adaptive optics atmospheric turbulence, residualsMetrology: Wavefront sensor(s)Correction: M5, M6, …

  10. From concept to sky testing: APE Active Phasing Experiment • Segmenting the VLT • Laboratory & on-sky evaluation of up to 3 phasing techniques • Integration of phasing into global wavefront control • On-sky by 2007

  11. MCAO simulation Adaptive optics Compensation of atmospheric turbulence

  12. 2 arc minutes field, l=2.5 mm 2 adaptive mirrors, 8000 actuators each 3 guide stars Not only simultations: Multi-conjugate Adaptive optics Demonstrator (MAD) on-sky by 2005 Sqrt stretch

  13. Cost estimate (capital investment, 2002 M€) • Diffraction-limited instrumentation • (acceptable étendue !) • Assumes “friendly site” • Average seismicity (0.2g) • Moderate altitude • Average wind speed • Moderate investment in infrastructures

  14. Cost estimates (industrial studies) Primary & secondary mirror segments; 1.8-m; polished, prices ex works. Blanks: SiC (2 suppliers A and B) with overocatings (3 suppliers 1, 2, 3) Glass-Ceramics (2 suppliers C and D) Polishing: 2 suppliers, only one shown (both agree within 10%)

  15. Maximum reliance on proven solutions, from supply to operations Optimized geometry (interface optics-mechanics) All parts fitting in 40-ft containers 1.6-m all-identical segments (~3000 units),single optical reference for polishing 12.8-m standard structural modules (integer multiple of segment size) Friction drive (bogies), hydraulic connection

  16. BOOSTEC ECM Meanwhile …

  17. Extremely Large Telescope Design Study

  18. ELT Design Study • The R&D part of a phase B • Objectives • Technology development towards a European ELT • Preparatory work for observatory design • Top level requirements • Academic & industrial synergy • Design-independent • Proposal to EC within FP6 - Approved • 39 partners, 47 WPs / Tasks • 42 M€ total, 22 M€ requested • Timescale 2005-2008 OWL & ELT Design Study - Nov-2004 - Slide 23

  19. ELT Design - Outline Wavefront control technologies • Low-cost, high accuracy actuators (up to 10,000 needed) • Low-cost, high accuracy metrology systems (up to 20,000) • Integrated control systems, APE • 7-segments breadboard, exposed to natural wind Adaptive optics • Development of ultra-thin adaptive mirrors • Control strategies • Subsystems conceptual design Materials & processes (e.g. SiC for segments) Composite materials for specific structural elements Magnetic levitation (telescope kinematics) Site search Science instruments designs OWL & ELT Design Study - Nov-2004 - Slide 24

  20. WEB WEB OWL & ELT Design Study - Nov-2004 - Slide 25

  21. Silicon Carbide prototypes • 1-m class, 8 pcs., different overcoatings • 4 blanks already at ESO • Explore overcoating & figuring processes,check for bimetallic effects • Advantages • Stiffer, lighter, better thermo-mechanicalproperties (than glass) • Higher control bandwidth (position) • Hardness • Lighter, stiffer telescope structure • ~20 years of development, space-qualified • Potentially cost-effective if appropriate design • BUT • Needs qualification for segmented apertures OWL & ELT Design Study - Nov-2004 - Slide 26

  22. Friction drive breadboard OWL & ELT Design Study - Nov-2004 - Slide 27 Mandatory – Hydraulic pads / tracks not an option !

  23. 2000 2005 2010 2015 2020 Phase A Phase A review ELT Design Study APE on sky Phase B Site selection First light (50-m) Completion Phase C/D Start of science (60-m) Groundbreaking Timeframe Driven by funding, not by technology

  24. OWL in brief A concept already at an advanced stage of design • Design supported by analysis & competitive industrial studies • Cost estimate > 50% completed, supported by competitive studies • Cost-effective design principles & solutions allow major jump in capability Substantial science at an early stage European-wide technology & concepts development • Industrial & academic synergy • ELTs “building blocks”, design-independent Prominent role of industry from earliest phase of design • Design minimizes industrial risks • Industrial solutions to design / fabrication / integration / maintenance • R&D focused on critical areas • Ample business opportunities – in R&D and serial production

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