IAU Joint Discussion 8

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.htm
  l

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/s
  cience_case_march16.htm

17
High Dynamic Range Telescope

• Design developed by
• Univ. of Hawaii
• 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 _at_ 0.14-m (NF)
• six _at_ 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 Technology DevelopmentsTelescope
Optics
46
Required Technology DevelopmentsTelescope
Optics
47
Required Technology DevelopmentsAdaptive Optics
48
Required Technology DevelopmentsAdaptive Optics
49
Required Technology DevelopmentsAdaptive Optics
50
Required Technology DevelopmentsAdaptive Optics
51
Required Technology DevelopmentsInstruments

• 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

52
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