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Future Giant Telescope (FGT) Projects and Their Technological Challenges

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

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Future Giant Telescope (FGT) Projects and Their Technological Challenges

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  1. Future Giant Telescope (FGT) Projects and Their Technological Challenges IAU Joint Discussion 8 July 17, 2003 Larry Stepp

  2. Outline • Introduction: how FGTs will advance beyond current-generation telescopes • A brief history of FGTs • Current concepts for FGTs • Technology challenges common to all

  3. 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

  4. Mayall  Keck • 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 350 tonnes 270 tonnes

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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

  10. 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

  11. 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

  12. 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

  13. 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

  14. 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

  15. 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

  16. 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

  17. 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

  18. 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

  19. 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

  20. 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

  21. 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

  22. 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

  23. 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

  24. 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

  25. 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

  26. 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

  27. 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

  28. 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.

  29. 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

  30. California Extremely Large Telescope (CELT) Interesting Features of Concept: • Scaled up Keck design with 1080 segments arranged in 91 rafts • Large Nasmyth platforms

  31. 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

  32. 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/

  33. 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

  34. Giant Segmented Mirror Telescope Interesting Features of Concept: • Prime focus instrument • Aperture stop at secondary • Adaptive secondary

  35. 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

  36. 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/

  37. 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

  38. Euro50 Interesting Features of Concept: • Adaptive secondary with composite face sheet • F/5 focal reducer for seeing-limited observing

  39. 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

  40. 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/

  41. Overwhelming Large Telescope (OWL) • Design by European Southern Observatory • Site: TBD Design Concept for OWL From OWL web site

  42. 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

  43. 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

  44. 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/

  45. Required Development Possibly Required 75-cm lightweight segment Required Technology Developments:Telescope & Optics

  46. Required Development Possibly Required Required Technology Developments:Telescope & Optics

  47. Required Development Possibly Required Required Technology Developments:Adaptive Optics

  48. Required Development Possibly Required Required Technology Developments:Adaptive Optics

  49. Required Development Possibly Required LLNL – ESO – CfAO sum-frequency fiber laser Required Technology Developments:Adaptive Optics

  50. Required Development Possibly Required Required Technology Developments:Adaptive Optics

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