The Giant Segmented Mirror Telescope Euro 50 GSMT

The Giant Segmented Mirror Telescope Euro 50 - 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 30 m telescope contemporary with NGST. Euro 50 - 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 Program Manager System Scientist Steve Strom Larry Stepp Brooke Gregory Admin. Assistant Jennifer Purcell Opto-Mechanical Controls Adaptive Optics Instruments Myung Cho George Angeli Ellerbroek - Gemini Barden - NOAO Mechanical Designer Structures Optics Sites Rick Robles Paul Gillett Hansen - Gemini Walker - NOAO Euro 50 - 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 Euro 50 - 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. 4 m < < 1. 1 m 3 m < < 25 m 1 m < < 2. 5 m 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 Euro 50 - 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) Euro 50 - 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 Euro 50 - 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 Euro 50 - 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 300 mw laser launched from laser room on Cerro Tololo Euro 50 - 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 fullscale 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 M 1 is above the EL axis - open to the wind flow (similar to concepts for future larger telescopes) Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Gemini 8 -meter Telescope Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Sensor locations 3 -axis anemometers Pressure sensors, 32 places Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Sensor Locations Ultrasonic anemometer Euro 50 - GSMT - XLT Meeting Pressure sensors LMS, 08/02/02 AURA New Initiatives Office

Simultaneous Animations (c 00030 oo) Wind Pressure (N/m 2) Mirror Deformation (microns) Wind Speed at 5 Locations (m/sec) Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Controls Approach: Hierarchical Subsystems LGS MCAO ~100 Zernike modes spatial & temporal avg ~50 AO (M 2) spatial & temporal avg ~20 spatial avg a. O (M 1) temporal avg ~10 spatial avg Secondary rigid body 2 spatial & temporal avg Main Axes 0. 001 0. 1 1 10 100 Bandwidth [Hz] Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 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 Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Optical Design Optical design: M 1 diameter: M 1 focal ratio: Classical Cassegrain 30 meters f/1 M 2 diameter: 2 meters M 2 focal ratio: f/18. 75 Euro 50 - 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 M 2 supported on tripod structure Elevation axis behind M 1 • Span between elevation bearings is less than M 1 diameter • Allows direct load path Euro 50 - 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 M 2 support Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Initial Point Design Structure Plan View of Structure Pattern of segments Gemini Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Initial Structural Analysis Horizon Pointing - Mode 1 = 2. 16 Hz Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

A Few Parameters from the Structural Analysis 1. Total weight of elevation structure – 700 tonnes 2. Total moving weight – 1400 tonnes 3. Gravity deflections ~ 5 -25 mm 1. Primarily rigid-body tilt of elevation structure 4. Lowest resonant frequencies ~ 2 Hz Large size and low resonant frequency make wind buffeting a key issue. Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Current structural concept Euro 50 - 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 Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

One-piece Central Raft Euro 50 - 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 Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Controllable Elements Active Systems: • • M 2 rigid body motion – ~ 5 -10 Hz – Five axes M 1 segment rigid body position – ~ 1 Hz – Piston, tip & tilt M 1 segment figure control – Based on look-up table ~ 0. 1 Hz – Astigmatism, focus, trefoil, coma Active structural elements – Active alignment – Active damping Euro 50 - 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 Euro 50 - 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. Euro 50 - 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 Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS) Located at prime focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Multi-Object Multi-Fiber Optical Spectrograph (MOMFOS) Located at prime focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Diffraction-limited Coronagraph Located at co-moving Cassegrain focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Instrument Locations Prime Focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Instrument Locations Co-moving Cassegrain Focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Instrument Locations Fixed-gravity Cassegrain Focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Instrument Locations MCAO-fed Nasmyth Focus Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

MCAO System Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Mayall, Gemini and GSMT Enclosures at same scale Mayall GSMT Gemini Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Mc. Kale Center – Univ of Arizona Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

GSMT – at same scale Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office

Some Possible GSMT Enclosure Designs Euro 50 - 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 Euro 50 - 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 Euro 50 - GSMT - XLT Meeting LMS, 08/02/02 AURA New Initiatives Office