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Innovative Telescope Design Study for Next Decade

Feasibility, progress of technology, active optics, optical figuring, adaptive optics, mechanical design, metrology, correction techniques, adaptive optics simulation, ELT design study, materials and processes in telescope design, silicon carbide prototypes.

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Innovative Telescope Design Study for Next Decade

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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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