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 tonnes 270 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
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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
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A Brief History of Future Giant TelescopesThe Kitt Peak Next Generation Telescope
• 25-m telescope• Segmented f/1 primary• Radio-telescope style mount• Concept from 1977
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A Brief History of Future Giant TelescopesThe National New Technology Telescope (NNTT)
• 16-m telescope• MMT-type • Four 8-m f/1.8 primary
mirrors• Concept from 1986
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A Brief History of Future Giant TelescopesMore Concepts Were Advanced in the Early 1990s
J. R. P. Angel, Filled Aperture Telescopes in the Next Millennium, SPIE 1236, 1990.
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, 1992.
M. Mountain, What is beyond the current generation of ground-based 8-m to 10-m class telescopes and the VLT-I?, SPIE 2871, 1996.
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, 1996.
V. V. Sytchev, V. B. Kasperski, S. M. Stroganova, V. I. Travush, On conceptual design options of a large optical telescope of 10...25 metre class, SPIE 2871, 1996.
AURA New Initiatives Office
Current Concepts for FGTsLarge 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
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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
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Large Aperture Telescope (LAT)
Design Parameters• Optical design: TBD
• Primary mirror diameter 20-m to 36-m
• Primary mirror focal ratio TBD (~ f/1)
• Secondary mirror diameter TBD
• Final focal ratio TBD
• 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 CN2 profile
More information is available at:http://astrosun.tn.cornell.edu/atacama/atacama.html
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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 20-20 interferometer
AURA New Initiatives Office
Magellan 20
Design Parameters• Optical design: Aplanatic Gregorian
• Primary mirror diameter 26-m (22-m equiv.)
• Primary mirror focal ratio f/0.7
• Secondary mirror diameter 2.5-m
• Final focal ratio f/10
• Field of View: 12’ - 20’
• Instrument locations: Nasmyth
Nasmyth (vertical)
Cassegrain
• Elevation axis location: Below primary mirror
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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:http://helios.astro.lsa.umich.edu/magellan/intro/science_case_march16.htm
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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
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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
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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 ratio f/1
• Secondary mirror diameter six @ 0.14-m (NF)
six @ 2.3-m (WF)
• Tertiary mirror diameter 7-m
• Final focal ratio f/15 (NF); f/1.9 (WF)
• Field of View: 3” (NF); 2 degrees (WF)
• Instrument locations: Central
• Elevation axis location: Above primary mirror
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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:http://www.ifa.hawaii.edu/users/kuhn/hdrt.html
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 ratio f/1
• Secondary mirror diameter 2.5-m to 5-m
• Final focal ratio f/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:http://www.astrsp-mrs.fr/denis/ngcfht/ngcfht.html
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
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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
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Very Large Optical Telescope (VLOT)
Design Parameters• Optical design: Ritchey-Chrétien
• Primary mirror diameter 20-m
• Primary mirror focal ratio f/1
• Secondary mirror diameter 2.5-m
• Final focal ratio f/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:http://www.hia-iha.nrc-cnrc.gc.ca/VLOT/index.html.
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 ratio f/1.5
• Secondary mirror diameter 3.96-m
• Tertiary mirror major axis 4.38-m
• Final focal ratio f/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:http://celt.ucolick.org/
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
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Giant Segmented Mirror Telescope
Design Parameters• Optical design: Cassegrain (or R-C)
• Primary mirror diameter 32-m (30-m equiv.)
• Primary mirror focal ratio f/1
• Secondary mirror diameter 2-m
• Final focal ratio f/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:www.aura-nio.noao.edu/
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 PalmaDesign 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 ratio f/0.85
• Secondary mirror diameter 4-m
• Final focal ratio f/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:http://www.astro.lu.se/~torben/euro50/
AURA New Initiatives Office
Overwhelming Large Telescope (OWL)
• Design by European Southern Observatory
• Site: TBD
Design Concept for OWL
From OWL web site
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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 ratio f/1.42
• Secondary mirror (M2) diameter 26-m
• M3 diameter 8.1-m
• M4 diameter 8.2-m
• M5 diameter 3.5-m
• Final focal ratio f/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:http://www.eso.org/projects/owl/
AURA New Initiatives Office
Required Technology Developments:Telescope & Optics
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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 CN2 distribution
Required Development
Possibly Required
AURA New Initiatives Office
Required Technology Developments:Adaptive Optics
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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 CN2 distribution
Required Development
Possibly Required
AURA New Initiatives Office
Required Technology Developments:Adaptive Optics
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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 CN2 distribution LLNL – ESO – CfAO
sum-frequency fiber laser
Required Development
Possibly Required
AURA New Initiatives Office
Required Technology Developments:Adaptive Optics
LAT
M20
HDRT
LPT
VLOT
CELT
GSMT
E50
OWL
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 CN2 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