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


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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

  • 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:

  • 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




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