AURA New Initiatives Office IAU Joint Discussion 8 July 17, 2003 Larry Stepp Future Giant Telescope (FGT) Projects and Their Technological Challenges

AURA New Initiatives Office Outline Introduction: how FGTs will advance beyond current- generation telescopes A brief history of FGTs Current concepts for FGTs Technology challenges common to all

AURA New Initiatives Office Current-Generation Telescopes 8- to 10-meter telescopes have achieved better performance at lower relative cost by reducing the size and mass of telescope & enclosure –Improvements in polishing and testing techniques have enabled faster primary mirrors –Active optics has achieved tighter alignment tolerances and enabled mirrors to be made lightweight –Faster primaries, lighter mirrors, alt-azimuth mounts & FEA have resulted in smaller, stiffer telescope structures –Smaller, stiffer structures have allowed enclosures to be smaller and better ventilated, improving local seeing As a result, sub-half-arc-second images are becoming commonplace

AURA New Initiatives Office Mayall  Keck 350 tonnes270 tonnes Cost in 1973: $10.6 M Adjusted to 1992: $33.7 M Projected cost of 10m in 1992: $400 M Actual cost of Keck 10m telescope in 1992: $110 M

AURA New Initiatives Office Future Giant Telescopes FGTs will continue the trends of the current generation –Faster primary focal ratios –Relatively lighter structures And they will advance beyond the Current Generation –Integral adaptive optics systems –Smart structures This will enable FGTs to have: –An order of magnitude more light-gathering power –Better image quality and resolution Diffraction-limited at > 1 micron However, significant technological challenges must be solved to make this possible

AURA New Initiatives Office A Brief History of Future Giant Telescopes The Kitt Peak Next Generation Telescope 25-m telescope Segmented f/1 primary Radio-telescope style mount Concept from 1977

AURA New Initiatives Office A Brief History of Future Giant Telescopes The National New Technology Telescope (NNTT) 16-m telescope MMT-type Four 8-m f/1.8 primary mirrors Concept from 1986

AURA New Initiatives Office A Brief History of Future Giant Telescopes More Concepts Were Advanced in the Early 1990s J. R. P. Angel, Filled Aperture Telescopes in the Next Millennium, SPIE 1236, A. Ardeberg, T. Andersen, B. Lindberg, M. Owner-Petersen, T. Korhonen, P. Søndergård, Breaking the 8m Barrier - One Approach for a 25m Class Optical Telescope, ESO Conf. and Workshop Proc. No. 42, M. Mountain, What is beyond the current generation of ground-based 8-m to 10-m class telescopes and the VLT-I?, SPIE 2871, F. N. Bash, T. A. Sebring, F. B. Ray, L. W. Ramsey, The extremely large telescope: A twenty-five meter aperture for the twenty-first century, SPIE 2871, V. V. Sytchev, V. B. Kasperski, S. M. Stroganova, V. I. Travush, On conceptual design options of a large optical telescope of metre class, SPIE 2871, 1996.

AURA New Initiatives Office Current Concepts for FGTs Large Aperture Telescope (LAT) LAT Consortium –Cornell –Chicago –Illinois –Northwestern Site: high Atacama desert or Antarctica Design concept for LAT From a presentation by Ed Kibblewhite

AURA New Initiatives Office Large Aperture Telescope (LAT) Interesting Features of Concept: Adaptive primary mirror –Design shown would have 36-m primary with 28-m adaptive central zone Science goals emphasize IR and sub-millimeter wavelengths Low PWV sites provide logistical challenges

AURA New Initiatives Office Large Aperture Telescope (LAT) Design Parameters Optical design:TBD Primary mirror diameter 20-m to 36-m Primary mirror focal ratioTBD (~ f/1) Secondary mirror diameterTBD Final focal ratioTBD Field of View: 5’ - 10’ Instrument locations: Cassegrain Elevation axis location:Below primary mirror

AURA New Initiatives Office Large Aperture Telescope (LAT) Key Technical Challenges –Cost-effective fabrication of lightweight, off-axis aspheric segments –Structure needs high damping –Momentum compensation for adaptive segments –Efficient segment co-phasing systems –Laser guidestar beacons –Site survey studies of C N 2 profile More information is available at:

AURA New Initiatives Office Magellan 20 Partner organizations include: –Carnegie –Harvard –Smithsonian –MIT –Arizona –Michigan Site: Las Campanas, Chile Design Concept for Magellan 20 From a presentation by Roger Angel

AURA New Initiatives Office Magellan 20 Interesting Features of Concept: Primary consists of seven 8.4-m mirrors Segmented, adaptive secondary Ground-conjugate adaptive optics Allows later incorporation into a interferometer

AURA New Initiatives Office Magellan 20 Design Parameters Optical design:Aplanatic Gregorian Primary mirror diameter 26-m (22-m equiv.) Primary mirror focal ratiof/0.7 Secondary mirror diameter2.5-m Final focal ratiof/10 Field of View: 12’ - 20’ Instrument locations: Nasmyth Nasmyth (vertical) Cassegrain Elevation axis location:Below primary mirror

AURA New Initiatives Office Magellan 20 Key Technical Challenges –Fabrication & testing of highly-aspheric 8.4-m off-axis segments –Segmented adaptive secondary mirror –Laser guidestar beacons –Multi-conjugate adaptive optics More information is available at:

AURA New Initiatives Office High Dynamic Range Telescope Design developed by: –Univ. of Hawai’i Site: Mauna Kea, Hawai'i –(replace the CFHT) Design concept for HDRT From a paper by Kuhn et al

AURA New Initiatives Office High Dynamic Range Telescope Interesting Features of Concept: Rapidly switchable narrow-field & wide-field modes Segmented secondary mirrors Concept for bi-parting enclosure Adaptive structure

AURA New Initiatives Office High Dynamic Range Telescope Design Parameters Optical design:Gregorian (NF) 3-mirror anastigmat (WF) Primary mirror diameter 22-m (16-m equiv.) Primary mirror focal ratiof/1 Secondary mirror 0.14-m (NF) 2.3-m (WF) Tertiary mirror diameter7-m Final focal ratiof/15 (NF); f/1.9 (WF) Field of View: 3” (NF); 2 degrees (WF) Instrument locations: Central Elevation axis location:Above primary mirror

AURA New Initiatives Office High Dynamic Range Telescope Key Technical Challenges –Fabrication of & testing of 6.5-m off-axis aspheric primary mirror segments –Fabrication & testing of 2.3-m off-axis secondary mirror segments –Adaptive telescope structure –Laser guidestar beacons More information is available at:

AURA New Initiatives Office Large Petal Telescope Design developed by: –Obs. Astron. Marseille- Provence –Obs. Astron. de Paris Site: Mauna Kea, Hawai'i –(replace the CFHT) Design concept for LPT From a paper by Burgarella et al

AURA New Initiatives Office Large Petal Telescope Interesting Features of Concept: Primary consists of six or eight 8-m sector-shaped, meniscus segments 3-mirror or 4-mirror optical design Simultaneous use of 6-8 instruments Adaptive telescope structure

AURA New Initiatives Office Large Petal Telescope Design Parameters Optical design:3- or 4-mirror anastigmat Primary mirror diameter 20-m + Primary mirror focal ratiof/1 Secondary mirror diameter2.5-m to 5-m Final focal ratiof/5 to f/7.5 Field of View: 1 degree Instrument locations: Cassegrain Elevation axis location:Below primary mirror

AURA New Initiatives Office Large Petal Telescope Key Technical Challenges –Fabrication & testing of 8-m off-axis aspheric primary mirror segments –Fabrication & testing of secondary mirror –Adaptive telescope structure –Multi-conjugate adaptive optics –Laser guidestar beacons More information is available at:

AURA New Initiatives Office Very Large Optical Telescope (VLOT) Design developed by: –HIA –AMEC Site: Mauna Kea, Hawai'i –(replace the CFHT) Design Concept for VLOT AMEC Dynamic Structures

AURA New Initiatives Office Very Large Optical Telescope (VLOT) Interesting Features of Concept: Considering concept with 8-m diameter central mirror surrounded by sector-shaped smaller segments Calotte dome concept

AURA New Initiatives Office Very Large Optical Telescope (VLOT) Design Parameters Optical design:Ritchey-Chrétien Primary mirror diameter 20-m Primary mirror focal ratiof/1 Secondary mirror diameter2.5-m Final focal ratiof/15 Field of View: 20’ Instrument locations: Nasmyth (vertical) Elevation axis location:Below primary mirror

AURA New Initiatives Office Very Large Optical Telescope (VLOT) Key Technical Challenges –Cost-effective fabrication of lightweight, off-axis aspheric segments –Fabrication & testing of secondary mirror –Laser guidestar beacons –Multi-conjugate adaptive optics –Laser guidestar beacons More information is available at:

AURA New Initiatives Office California Extremely Large Telescope (CELT) CELT Partnership –Caltech –Univ. of California Site: TBD (Mauna Kea or northern Chile or Mexico) Design concept for CELT From the CELT Greenbook

AURA New Initiatives Office Interesting Features of Concept: Scaled up Keck design with 1080 segments arranged in 91 rafts Large Nasmyth platforms California Extremely Large Telescope (CELT)

AURA New Initiatives Office Design Parameters Optical design:Ritchey-Chrétien Primary mirror diameter 30-m Primary mirror focal ratiof/1.5 Secondary mirror diameter3.96-m Tertiary mirror major axis4.38-m Final focal ratiof/15 Field of View: 20” Instrument locations: Nasmyth Elevation axis location:Above primary mirror California Extremely Large Telescope (CELT)

AURA New Initiatives Office California Extremely Large Telescope (CELT) Key Technical Challenges –Cost-effective fabrication of 1080 off-axis aspheric primary mirror segments –Fabrication & testing of secondary mirror –Fast tip-tilt-piston of secondary and tertiary mirrors –Efficient segment co-phasing systems –Laser guidestar beacons –Multi-conjugate adaptive optics More information is available at:

AURA New Initiatives Office Giant Segmented Mirror Telescope Design by AURA New Initiatives Office –NOAO –Gemini Site: TBD (Mauna Kea or northern Chile or Mexico) Design Concept for GSMT From animation by Rick Robles

AURA New Initiatives Office Giant Segmented Mirror Telescope Interesting Features of Concept: Prime focus instrument Aperture stop at secondary Adaptive secondary

AURA New Initiatives Office Giant Segmented Mirror Telescope Design Parameters Optical design:Cassegrain (or R-C) Primary mirror diameter 32-m (30-m equiv.) Primary mirror focal ratiof/1 Secondary mirror diameter2-m Final focal ratiof/18.75 Field of View: 20” Instrument locations: Prime focus Nasmyth Cassegrain (moving & fixed) Elevation axis location:Below primary mirror

AURA New Initiatives Office Giant Segmented Mirror Telescope Key Technical Challenges –Cost-effective fabrication of 618 off-axis aspheric primary mirror segments –Efficient segment co-phasing systems –Adaptive secondary mirror –Laser guidestar beacons –Multi-conjugate adaptive optics –Adaptive telescope structure More information is available at:

AURA New Initiatives Office Euro50 Euro50 partners –Lund University –Inst. de Astrofisica de Canarias –Dept. of Physics, Galway, Ireland –Tuorla Observatory –Optical Science Lab. –National Physical Lab. Site: La Palma Design Concept for Euro50 From Euro50 web site

AURA New Initiatives Office Euro50 Interesting Features of Concept: Adaptive secondary with composite face sheet F/5 focal reducer for seeing-limited observing

AURA New Initiatives Office Euro50 Design Parameters Optical design:Gregorian Primary mirror diameter 50-m Primary mirror focal ratiof/0.85 Secondary mirror diameter4-m Final focal ratiof/13; also: f/5; f/16; f/20 Field of View: 4’ Instrument locations: Nasmyth Folded Cassegrain Elevation axis location:Below primary mirror

AURA New Initiatives Office Euro50 Key Technical Challenges –Cost-effective fabrication of 618 off-axis aspheric primary mirror segments –Efficient segment co-phasing systems –Adaptive secondary mirror –Laser guidestar beacons –Multi-conjugate adaptive optics More information is available at:

AURA New Initiatives Office Overwhelming Large Telescope (OWL) Design by European Southern Observatory Site: TBD Design Concept for OWL From OWL web site

AURA New Initiatives Office Overwhelming Large Telescope (OWL) Interesting Features of Concept: Spherical primary mirror Flat segmented secondary mirror Three aspheric mirrors Elevation assembly recessed into ground Mount tied to ground by multiple drive bogies

AURA New Initiatives Office Overwhelming Large Telescope (OWL) Design Parameters Optical design:Six-mirror design Primary mirror (M1) diameter 100-m Primary mirror focal ratiof/1.42 Secondary mirror (M2) diameter26-m M3 diameter8.1-m M4 diameter8.2-m M5 diameter3.5-m Final focal ratiof/7.5 Field of View: 10’ Instrument locations: Central Elevation axis location:Above primary mirror

AURA New Initiatives Office Overwhelming Large Telescope (OWL) Key Technical Challenges –Fabrication of large numbers of lightweight segments –Active structure to move corrector –Efficient segment co-phasing systems –Multi-conjugate adaptive optics –2.4-m adaptive flat mirror –3.5-m adaptive curved mirror More information is available at:

AURA New Initiatives Office Required Technology Developments: Telescope & Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Lightweight 1-m to 2-m segments Large numbers of aspheric segments Fab & test of large aspheric segments Active/adaptive structure Fab & testing of large, convex M2s High-reflectivity durable coatings Efficient segment co-phasing systems Large, fast tip-tilt-piston mirrors 75-cm lightweight segment Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Telescope & Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Lightweight 1-m to 2-m segments Large numbers of aspheric segments Fab & test of large aspheric segments Active/adaptive structure Fab & testing of large, convex M2s High-reflectivity durable coatings Efficient segment co-phasing systems Large, fast tip-tilt-piston mirrors Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Adaptive Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Improved analysis & simulation Large adaptive mirrors MOEMS deformable mirrors for EXAO MCAO system designs Laser guidestar beacons Large-format, fast, low noise detectors Wavefront rec. & fast signal processors Site testing of C N 2 distribution Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Adaptive Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Improved analysis & simulation Large adaptive mirrors MOEMS deformable mirrors for EXAO MCAO system designs Laser guidestar beacons Large-format, fast, low noise detectors Wavefront rec. & fast signal processors Site testing of C N 2 distribution Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Adaptive Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Improved analysis & simulation Large adaptive mirrors MOEMS deformable mirrors for EXAO MCAO system designs Laser guidestar beacons Large-format, fast, low noise detectors Wavefront rec. & fast signal processors Site testing of C N 2 distribution LLNL – ESO – CfAO sum-frequency fiber laser Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Adaptive Optics LATLAT M20M20 HDRTHDRT LPTLPT VLOTVLOT CELTCELT GSMTGSMT E50E50 OWLOWL Improved analysis & simulation Large adaptive mirrors MOEMS deformable mirrors for EXAO MCAO system designs Laser guidestar beacons Large-format, fast, low noise detectors Wavefront rec. & fast signal processors Site testing of C N 2 distribution Required Development Possibly Required

AURA New Initiatives Office Required Technology Developments: Instruments Affordable large near-IR detectors Affordable large mid-IR detectors Advanced image slicers for IFUs Fiber positioners MOEMS slit masks for multi-object spectroscopy Large-format volume-phase holographic gratings Large-format immersed silicon gratings Large lenses & filters

AURA New Initiatives Office Call For International Cooperation Our needs are so similar and our resources are limited, close cooperation is essential: Joint ventures where sensible Coordination to ensure studies are complementary Open sharing of information as much as possible