The Giant Segmented Mirror Telescope
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The Giant Segmented Mirror Telescope Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office The USA Decadal Review • In May 2000, the US astronomy decadal review committee recommended, as its highest priority ground-based initiative, the construction of a 30-meter Giant Segmented Mirror Telescope (GSMT) • In response, AURA formed a New Initiatives Office (NIO) to support scientific and technical studies leading to the creation of a GSMT • NIO is a joint venture of the National Optical Astronomy Observatory (NOAO) and the Gemini Observatory • Goal is to ensure broad astronomy community access to a 30m telescope contemporary with NGST. Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office N IO Organization NIO Management Board William Smith -- President of AURA Jeremy Mould -- Director of NOAO Matt Mountain -- Director of Gemini Observatory Project Scientist Steve Strom Program Manager Larry Stepp System Scientist Brooke Gregory Admin. Assistant Jennifer Purcell Opto-Mechanical Myung Cho Controls George Angeli Adaptive Optics Ellerbroek - Gemini Instruments Barden - NOAO Mechanical Designer Rick Robles Structures Paul Gillett Optics Hansen - Gemini Sites Walker - NOAO Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office AURA New Initiatives Office Approach to GSMT Design Three Parallel efforts: • Understand the scientific context for GSMT in NGST / ALMA era • Develop the key science requirements • Address challenges common to all ELTs • Site testing and selection • Cost-effective segment fabrication • • • • Characterization of wind loading Hierarchical control systems Adaptive optics Cost control techniques • Develop a Point Design • Based on initial science goals & instrument concepts Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Science Programs Science Theme Large Scale Structure Planet Formation Environments Tomography of Galaxies and pre-Galactic Fragments Resolved Stellar Populations High-dynamic range science Field of View Wide: >20 arc minute Narrow: <5 arc second 2 arc minute 2 arc minunte Narrow: <5 arc second Wavelength 0.4m < < 1.1 m 3m < < 25 m 1m < < 2.5m 1m < < 2.5 m 1m < < 2.5m Image quality Seeing limited < 0.5 arc second Diffraction-limited low-emissivity < 0.1 arcsecond Diffraction limited Strehl ratio > 0.9 Instrumentation Multi-Object Spectrograph R = 1000 - 5000 High-resolution spectrograph R = 100,000 Deployable IFU spectrograph R = 5000 – 10,000 Imager Coronagraph Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Site Testing and Selection Survey of candidate sites by remote sensing (satellite data) • Regions of interest: • Mauna Kea • Western United States and Mexico • Chile • Parameters determined: • Cloud cover • Precipitable water vapor • Collaborators: • Cornell • ESO • University of Tokyo • CELT • UNAM & INAOE (Mexico) Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Site Testing and Selection Construction of turbulence profilometer (MASS – Multi-Aperture Scintillation Sensor) • Uses scintillation measurements of a single star to measure: • Isoplanatic angle, characteristic strengths and altitudes of the few dominant turbulence layers • Integral seeing producing by the whole atmosphere Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Site Testing and Selection Atmospheric turbulence modeling and measuring • Direct measurements of seeing and wind speed • Computational fluid dynamics • Collaborators • CELT • UNAM (Mexico) • Cornell Digital elevation model of Chajnantor region Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Site Testing and Selection Sodium layer measurements at Cerro Tololo • Collaborating on Gemini study to answer questions about variation of sodium layer height, thickness and column density with: • Latitude • Season • Time of night 300mw laser launched from laser room on Cerro Tololo Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Characterization of Wind Loading Test at Gemini South Opportunity arose during integration of Gemini South to do a full-scale wind test in realistic conditions Gemini enclosure has large vent gates – permits testing a range of enclosure conditions Gemini dummy mirror has equivalent properties as the real primary mirror, but can be instrumented Gemini M1 is above the EL axis - open to the wind flow (similar to concepts for future larger telescopes) Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Gemini 8-meter Telescope Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Sensor locations 3-axis anemometers Pressure sensors, 32 places Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Sensor Locations Ultrasonic anemometer Ultrasonic anemometer Euro50 - GSMT - XLT Meeting Pressure sensors LMS, 08/02/02 AURA New Initiatives Office Simultaneous Animations (c00030oo) Wind Pressure (N/m2) Mirror Deformation (microns) Wind Speed at 5 Locations (m/sec) Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Controls Approach: Hierarchical Subsystems LGS MCAO ~100 spatial & temporal avg ~50 AO (M2) spatial & temporal avg ~20 spatial avg aO (M1) temporal avg ~10 spatial avg Secondary rigid body 2 spatial & temporal avg Main Axes 0.001 Euro50 - GSMT - XLT Meeting 0.01 0.1 LMS, 08/02/02 1 10 100 AURA New Initiatives Office Point Design Key Features • Fast aspheric primary – Stigmatic image after two reflections • Radio telescope-type design • Structural advantages • Accommodates large instruments • Adaptive secondary – Wind-buffeting compensation – Atmospheric correction in IR, with low emissivity – First stage in higher-order adaptive systems • Prime focus instrument – Convenient plate scale for seeing-limited observations – Enables wide-field science Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Optical Design Optical design: M1 diameter: M1 focal ratio: Classical Cassegrain 30 meters f/1 M2 diameter: 2 meters M2 focal ratio: f/18.75 Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Radio Telescope Structural Design Lightweight steel truss structure Fast primary focal ratio Small secondary mirror M2 supported on tripod structure Elevation axis behind M1 • Span between elevation bearings is less than M1 diameter • Allows direct load path Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Initial Point Design Structure Concept developed by Joe Antebi of Simpson Gumpertz & Heger • Based on radio telescope • Space frame truss • Single counterweight • Cross bracing of M2 support Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Initial Point Design Structure Plan View of Structure Pattern of segments Typical 'raft', 7 mirrors per raft 1.152 m mirror across flats Gemini Euro50 - GSMT - XLT Meeting LMS, 08/02/02 Special raft - 6 places, 4 mirrors per raft Circle, 30m dia. AURA New Initiatives Office Initial Structural Analysis Z X Y Output Set: Mode 1, 2.156537 Hz, Deformed(0.0673): Total Translation Horizon Pointing - Mode 1 = 2.16 Hz Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office A Few Parameters from the Structural Analysis • Total weight of elevation structure – 700 tonnes • Total moving weight – 1400 tonnes • Gravity deflections ~ 5-25 mm – Primarily rigid-body tilt of elevation structure • Lowest resonant frequencies ~ 2 Hz Large size and low resonant frequency make wind buffeting a key issue. Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Current structural concept Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Primary Mirror Segments • Segment dimensions – 1.15-m across flats -- 1.33-m corner to corner – 50 mm thickness • • • Number of segments: 618 Maximum departure from sphere 110 microns – Comparable to Keck Axial support is 18-point whiffletree – FEA Gravity deflection 15 nm RMS Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office One-piece Central Raft Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Stray Light Baffles If Needed Primary baffle: 14 m long Secondary baffle: 3 m diamater Fully baffled field of view: 5 arc min Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Controllable Elements Active Systems: • • • • M2 rigid body motion – ~ 5-10 Hz – Five axes M1 segment rigid body position – ~ 1 Hz – Piston, tip & tilt M1 segment figure control – Based on look-up table ~ 0.1 Hz – Astigmatism, focus, trefoil, coma Active structural elements – Active alignment – Active damping Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Controllable Elements Adaptive Systems: • • • • Adaptive mirror in prime focus corrector Adaptive secondary mirror – ~ 20-50 Hz – ~ 2400 actuators Multi-conjugate wide-field AO – – ~ 3 DMs; ~ 8500 actuators Laser Guide Stars High-order narrow-field conventional AO – ~ 10,000 – 50,000 actuators Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Active and Adaptive Optics will be integrated into Telescope and Instrument concepts from the start. Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Instruments • NIO currently developing design concepts for 5 instruments: – – – – – Multi-Object, Multi-Fiber, Optical Spectrograph – MOMFOS Near IR Deployable Integral Field Spectrograph – NIRDIF MCAO-fed near-IR imager Mid-IR, High Dispersion, AO Spectrograph – MIHDAS Diffraction-Limited Near IR Coronagraph Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS) Located at prime focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS) Located at prime focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Diffraction-limited Coronagraph Located at co-moving Cassegrain focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Instrument Locations Prime Focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Instrument Locations Co-moving Cassegrain Focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Instrument Locations Fixed-gravity Cassegrain Focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Instrument Locations MCAO-fed Nasmyth Focus Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office MCAO System Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Mayall, Gemini and GSMT Enclosures at same scale Mayall GSMT Gemini Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office McKale Center – Univ of Arizona Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office GSMT – at same scale Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Some Possible GSMT Enclosure Designs Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Plans for the Next 10 Months Complete “GSMT Book” in electronic form – will be available next month at: www.aura-nio.noao.edu Involve community in understanding GSMT scientific context Continue work on point design Develop integrated modeling of telescope response to disturbances (mainly wind) Continue site testing efforts Develop cost estimates & cost-reduction strategies Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office Plans for the Next 10 Months Develop collaborations to work on: • • • • • Site testing Segment fabrication methods Characterization of wind loading Adaptive optics Development of cost estimates and estimating methods Build partnership to proceed with GSMT design Euro50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office
