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TMT: the next generation of segmented mirror telescopes

TMT: the next generation of segmented mirror telescopes. Jerry Nelson, UCSC GTC Inauguration Seminar 2009 July 25. Outline. Project Introduction Telescope overview TMT key features Major science goals Science Instruments. TMT Mauna Kea. Best high-altitude seeing 4200 m. 3.

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TMT: the next generation of segmented mirror telescopes

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  1. TMT: the next generation of segmented mirror telescopes Jerry Nelson, UCSC GTC Inauguration Seminar 2009 July 25 GTC 2009Jul25

  2. Outline • Project Introduction • Telescope overview • TMT key features • Major science goals • Science Instruments GTC 2009Jul25

  3. TMT Mauna Kea • Best high-altitude seeing • 4200 m GTC 2009Jul25 3 ALMA and ELTs 2009

  4. NORTH A Mauna Kea 13N site Proposed Site Area Prevailing wind Mauna Kea Science Preserve Master Plan: Astronomy Precinct GTC 2009Jul25 ALMA and ELTs 2009

  5. Project Introduction • Time line • 2004 project start, design development • 2009 preconstruction phase • 2011 start construction • 2018 complete, first light, start AO science • Partnership • UC • Caltech • Canada • Japan • NSF? • Other nations? • Cost • 970M$ (2009$) GTC 2009Jul25

  6. GTC 2009Jul25

  7. What is TMT? • Thirty-meter aperture • Filled, segmented primary • Elevation axis in front of primary • Active and adaptive optics • UV to thermal IR • Broad range of instruments GTC 2009Jul25 ALMA and ELTs 2009

  8. TMT features • 14 - 200 times the sensitivity of 8 m telescopes (D2 - D4 gain) • 3 - 5 times the resolution of 8 m telescopes and JWST • 20 arcmin field of view • 5 AO modes • Pointing in < 3 min • Instrument change in < 10 min • Calotte enclosure GTC 2009Jul25

  9. Observatory Layout: Telescope LGSF launch telescope M2 support tripod M2 structural hexapod Tensional members LGSF beam transfer M2 hexagonal ring M2 support columns Elevation journal Nasmyth platform Laser room Azimuth cradle GTC 2009Jul25 M1 cell Azimuth truss

  10. TMT Optical Design:Ritchey Chrétien • M1 Parameters • ø30m, f/1, Hyperboloid • k = -1.000953 • Paraxial RoC = 60.0m • Sag = 1.8m • Asphericity = 29.3mm (entire M1) • M2 Parameters • ø3.1m, ~f/1, Convex hyperboloid, • k = -1.31823 • Paraxial RoC = -6.228m • Sag = ~650mm • Aspheric departure: 850 mm • M3 Parameters • Flat • Elliptical, 2.5 X 3.5m GTC 2009Jul25

  11. Segment Size GTC 2009Jul25

  12. Nasmyth Configuration: First Decade Instrument Suite GTC 2009Jul25

  13. Why build a 30-m telescope:huge aperture advantage • Seeing-limited observations and observations of resolved sources • Background-limited AO observations of unresolved sources • High-contrast AO observations of unresolved sources • High-contrast ExAO observations of unresolved sources GTC 2009Jul25

  14. Science Potential • Solar system detailed studies • Direct imaging planets around nearby stars • Stars and stellar evolution • Black holes and galaxies • Nearby galaxies • Distant galaxies and first light GTC 2009Jul25

  15. GTC 2009Jul25

  16. Distant Galaxies – TMT+AO Credit: M. Bolte TMT with AO angular resolution 100x better than seeing limited GTC 2009Jul25

  17. Primary Mirror Segments • TMT segmented mirror is an evolution of the Keck mirror • 36 segments, 1.8m, in each Keck telescope • 492 segments, 1.45m, in TMT • Polishing and segment module fabrication must be “mass produced” to cost and quality • TMT is working with industrial partners to compete production design, testing and cost GTC 2009Jul25

  18. Seven Segment Assembly – Top View Segment SupportAssembly (SSA) Design GTC 2009Jul25

  19. Seven Segment Assembly – Bottom View Segment SupportAssembly (SSA) Design GTC 2009Jul25

  20. Active Control Summary Selected a = 0.72 m for segment size Item Keck TMT segment size 0.9m 0.72m # segments 36 492 # edge sensors 168 2772 # actuators 108 1476 GTC 2009Jul25

  21. Adaptive Optics GTC 2009Jul25

  22. Adaptive Optics • Adaptive optics seriously introduces the concept of high speed, high bandwidth control • Primary aim is to remove rapidly varying atmospheric turbulence that causes image blur • Secondary bi-product is ability to remove both slowly varying and rapidly varying wavefront errors that are in the telescope • As currently envisioned and used, adaptive optics is only practical in the near infrared, not the visible. • Adaptive optics is technologically challenging! • Result is diffraction-limited performance • AO is revolutionary • For TMT resolution of 0.005 arcsec 100x better than atmosphere GTC 2009Jul25

  23. Basic Elements of Adaptive Optics • Atmospheric turbulence… • introduces wavefront and image quality degradations… • which can in principal be compensated by a wavefront corrector… • provided that they can be measured with a wavefront sensor… • observing a suitable reference star GTC 2009Jul25

  24. starlight Na Laser Tomography and MCAO Na laser beams (6 total) 35 arcsec Na layer (~10 km) “Meta-pupil” for a +/-1 arc min FoV 90km Light from 1 arcmin off axis Turbulent atmosphere (~15 km) DM conjugate to h ~ 10-12 km 30 m DM conjugate to h= 0 km

  25. TMT AO • NFIRAOS has two deformable mirrors- MCAO • 64x64 • 73x73 • NFIRAOS laser will produce 6 laser spots • Illuminates Na layer, 90km up in the atmosphere • 150 Watts Na power • One central spot, 5 perimeter spots • Two arc minute field of view • Atmosphere is tomographically reconstructed, then projected out in the direction of interest • Computationally intensive • Solve 38000x7000 control problem at 800 Hz GTC 2009Jul25

  26. LSE TMT AO Early Light Architecture • Narrow Field IR AO System (NFIRAOS) • MCAO LGS AO System • Mounted on Nasmyth Platform • Feeds 3 science instruments • Laser Guide Star Facility (LGSF) • Laser enclosure located within telescope azimuth structure • Conventional optics for beam transport • Laser launch telescope behind M2 • AO Executive Software(AOESW) NFIRAOS: - 190nm RMS WFS - 60x60 order system - 2 DMs, 6 LGS, 3 TTF WFS - 800Hz GTC 2009Jul25

  27. NFIRAOS Interfaces with Nasmyth Platform and Client Instruments Future (third) Instrument NFIRAOS Enclosure Service Platform Optics Bench and Instrument Support Structure BTO Path LGS WFS Optics Nasmyth Platform Interface IRIS Electronics Enclosure Nasmyth Platform GTC 2009Jul25

  28. NFIRAOS Optics Benches GTC 2009Jul25

  29. Science instruments GTC 2009Jul25

  30. TMT First Decade Instrument/Capability Suite GTC 2009Jul25 30

  31. TMT Early Light Instrument Suite GTC 2009Jul25

  32. imager filter wheels F/15 AO Focus 2’ WFS IFUs imager IRIS - Infrared imaging spectrometer IRIS dewar (at 77k) Grating Common spectrograph and camera for both IFUs GTC 2009Jul25

  33. IRMS - Infrared multislit spectrometer • 0.8 - 2.5 um cryogenic multi-slit spectrometer • 2.3 arcmin field of view • 0.06 arcsec sampling • 46 moveable slits 2.4” long • Covers entire Y, J, H or K band at R = 4660

  34. WFOS - Wide-field optical spectrograph • 0.31 - 1.1 um wavelength range • Observe up to 1500 objects over a 40.5 sq. arcmin FOV • Spectral resolution 300 - 7500 • Reflecting gratings / prism cross-dispersion, and fixed dichroic beamsplitter at 550nm • “Echellette” design provides up to 5 orders • Full wavelength coverage, even at highest resolution, for “discovery science” • Low resolution mode (single order) for maximum multiplex advantage

  35. Summary • TMT will be a 30-m telescope with AO capabilities from the start • ~ 190 nm rms wavefront error over 10 arcsec • First light 2018 • Very large and exciting science case • 8 instruments planned for the first decade • 3 instruments planned for first light • IRIS (an AO NIR integral field spectrograph and imager) • IRMS (an AO NIR multi object spectrometer (46 slits) • WFOS (a seeing-limited multiobject spectrometer with R<8000, and ~ 50 arcmin2coverage) GTC 2009Jul25

  36. www.tmt.org/foundation-docs/index.html Detailed Science Case 2007 Observatory Requirements Document Observatory Architecture Document Operations Concept Document TMT Construction Proposal Currently in use for funding proposals TMT Foundation Documents GTC 2009Jul25

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