Future Giant Telescope (fgt) Projects and Their Technological Challenges iau joint Discussion 8

Future Giant Telescope (FGT) Projects and Their Technological Challenges

• IAU Joint Discussion 8

• July 17, 2003

• Larry Stepp

Outline

• Introduction: how FGTs will advance beyond current-generation telescopes

• A brief history of FGTs

• Current concepts for FGTs

• Technology challenges common to all

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

Mayall  Keck

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

A Brief History of Future Giant Telescopes The Kitt Peak Next Generation Telescope

A Brief History of Future Giant Telescopes The National New Technology Telescope (NNTT)

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, 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.

Current Concepts for FGTs Large Aperture Telescope (LAT)

• LAT Consortium

• Cornell
• Chicago
• Illinois
• Northwestern

• Site: high Atacama desert or Antarctica

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

Large Aperture Telescope (LAT)

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

Magellan 20

• Partner organizations include:

• Carnegie
• Harvard
• Smithsonian
• MIT
• Arizona
• Michigan

• Site: Las Campanas, Chile

Magellan 20

• Interesting Features of Concept:

• Primary consists of seven 8.4-m mirrors

• Segmented, adaptive secondary

Magellan 20

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

High Dynamic Range Telescope

• Design developed by:

• Univ. of Hawai’i

• Site: Mauna Kea, Hawai'i

• (replace the CFHT)

High Dynamic Range Telescope

• Interesting Features of Concept:

• Rapidly switchable narrow-field & wide-field modes

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

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

Large Petal Telescope

• Design developed by:

• Obs. Astron. Marseille-Provence
• Obs. Astron. de Paris

• Site: Mauna Kea, Hawai'i

• (replace the CFHT)

Large Petal Telescope

• Interesting Features of Concept:

• Primary consists of six or eight 8-m sector-shaped, meniscus segments

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

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

Very Large Optical Telescope (VLOT)

• Design developed by:

• HIA
• AMEC

• Site: Mauna Kea, Hawai'i

• (replace the CFHT)

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

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

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.

California Extremely Large Telescope (CELT)

• CELT Partnership

• Caltech
• Univ. of California

• Site: TBD (Mauna Kea or northern Chile or Mexico)

California Extremely Large Telescope (CELT)

• Interesting Features of Concept:

• Scaled up Keck design with 1080 segments arranged in 91 rafts

• Large Nasmyth platforms

California Extremely Large Telescope (CELT)

• 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)

• 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/

Giant Segmented Mirror Telescope

• Design by AURA New Initiatives Office

• NOAO
• Gemini

• Site: TBD (Mauna Kea or northern Chile or Mexico)

Giant Segmented Mirror Telescope

• Interesting Features of Concept:

• Prime focus instrument

• Aperture stop at secondary

• Adaptive secondary

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

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/

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

Euro50

• Interesting Features of Concept:

• Adaptive secondary with composite face sheet

• F/5 focal reducer for seeing-limited observing

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

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/

Overwhelming Large Telescope (OWL)

• Design by European Southern Observatory

• Site: TBD

Overwhelming Large Telescope (OWL)

• Interesting Features of Concept:

• Spherical primary mirror

• Flat segmented secondary mirror

• Three aspheric mirrors

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

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/

Required Technology Developments: Telescope & Optics

Required Technology Developments: Telescope & Optics

Required Technology Developments: Adaptive Optics

Required Technology Developments: Adaptive Optics

Required Technology Developments: Adaptive Optics

Required Technology Developments: Adaptive Optics

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

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