The Thirty Meter Telescope
Jerry Nelson, UCSC
2005 December 8
Contents
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Lessons of History and Predicting the Future
Scientific Potential of TMT
TMT Organization
TMT conceptual design
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Overall structure
Optical design
Primary mirror
Segment geometry
Segment fabrication
Active control
Enclosure
• Adaptive Optics
• Status
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Predicting the future
• Proposed Future Ground Based Telescopes
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California Extremely Large Telescope (CELT)
20/20 (University of Arizona study)
Giant Magellan Telescope
Euro 50 (Lund University study)
OWL (ESO study)
TMT (merger of CELT, GSMT, VLOT)
30 m
30 m equivalent
20m
50m
100m (<60m)
30m
• Major Issues (mainly cost)
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mass production of optics
active control
adaptive optics
structural issues
enclosure/ weather protection
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Science Potential for TMT
• Increased angular resolution
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With AO can reach 0.007 arc second resolution (100x improvement)
Study morphological details of most distant galaxies (cosmology)
Study details for star and planet formation
Study stellar evolution in globular clusters
Quasars and Active Galactic Nuclei (black holes)
Solar system objects
• Increased light gathering power
– With TMT can collect 9x the energy from an object (over Keck)
– Spectroscopy of most distant objects known
– Planet searches and their study
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Scientific Potential
• Seeing limited observations
– 0.3-1.0 µm
– Scale 2.18 mm/arc second (f/15)
– Wide field of view available: 20 arcminutes
• Diffraction limited observations
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1-25µm, mainly 1-2.5µm
Thermal IR possible, but not most important
At 1 µm angular resolution of 7 mas
Resolution element size: 15µm (at f/15, 1 µm wavelength)
Large field of view: 1 arc minute at 1 µm with multi
conjugate AO
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Thirty Meter Telescope
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TMT is a project to build a 30-m telescope
UC and Caltech are partners (CELT) + Canada + AURA
Design and prototyping money is ~ here
$70M total needed
– $35 UC+Caltech (CELT) from Moore Foundation
– Canada contributes $17.5M
– AURA should contribute $17.5M (highly uncertain)
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Site is unknown (several candidates being studied)
Project manager (Gary Sanders from LIGO)
Project scientist (J. Nelson)
Project office in Pasadena
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TMT Project Organization
TMT Board
Ed Stone
Project Manager
Gary Sanders
Project Scientist
Jerry Nelson
System Engineering
George Angeli
Business Manager
David Goodman
Observatory Scientist
Dave Silva
Outreach
Doug Isbell
IT
Science Advisory Committee
Paul Hickson, Chair
ES&H/QA
Facility
Paul Gillett, Acting
Telescope
Larry Stepp
Instrumentation
Operations Design
Site Selection
Paul Gillett
Structure
Chris White
Adaptive Optics
Brent Ellerbroek
Observing Design
Enclosure
Joeleff Fitzimmons, Acting
Optics
Dan Blanco, Acting
Instruments
David Crampton
Observatory Software
Jennifer Dunn, Acting
Summit Facilities
Douglas Gray
Controls
Mark Sirota
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Support Facilities
Douglas Gray
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Original Point Designs
GSMT
www.aura-nio.noao.edu/
2005 December 8
CELT
http://celt.ucolick.org/
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VLOT
http://www.hia-iha.nrccnrc.gc.ca/VLOT/index.html
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Site Selection
• We have a team of research scientists studying potential
sites for TMT
• Sites are being studied in Chile, San Pedro Martir (Baja)
and Mauna Kea, HI
• Measurements include
– Weather (cloudiness, wind, temperature, humidity, dust)
– Atmospheric seeing (total seeing with DIMM’s, profile with MASS and
with SODAR’s)
• Expect to select qualified sites in 2007
• Hope for competition between qualified sites to host TMT
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TMT Optical Design
• Primary is 30m in diameter
– 738 segments, 1.2 m dia each
– Shape actively controlled (segment piston, tip, tilt)
– f/1.0 ellipsoid
• Final: f/15 Aplantic Gregorian
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Secondary 3.5m in diameter (concave)
20 arc minute field of view with 0.5 arc second images
1 arc minute FOV with 0.001 arc second images (design)
Science from 1° to 65° zenith angle
• Instruments at Nasmyth platforms
– Articulated tertiary allows direct feed to multiple instruments with
no additional optics (3 mirrors total)
– 2 platforms: 15x30 m
– Possible lower or upper platforms
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TMT Optics
20m
30m
3.58m
3.5m
3.32m
33.32m
30m Primary Mirror Concept
738  1.2m segments
each 0.040m thick
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TMT
Keck
TMT Reference Design
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32m
2m
40m
34m
20m
60m
Segment Fabrication
• Segments are off axis sections of ellipse
– Requirements: ~ 20 nm rms surface (better than Keck)
– ~ 90 µm deviation from sphere (Keck was ~ 100µm)
• Fabrication study contracts (3) in place: Sagem, Zygo, ITTTinsley
– Stressed mirror polishing (oap to sphere) favored by all
– Planetary polishing to increase efficiency (simultaneous polishing of
multiple mirrors)
– Low expansion material will be used
– Final figure corrections with ion figuring likely
• Segment warping harnesses (WH)
– Will remove low spatial frequency segment errors caused by testing
errors, polishing errors, support errors, thermal errors, alignment
errors
– Will ease tolerances (and costs) of fabrication, etc
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Planetary polishing to produce 800
segments
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Full stressing fixture
Planetary Stressed Mirror Polishing
Passive segment support
• Design work contracted to Hytec (Los Alamos)
• Basic requirements
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Support segments against gravity and thermal disturbances
Maintain desired surface figure to ~ 5 nm rms
Accurately maintain segment in desired location
Provide interface between actuators and mirror
Provide stiff (50Hz natural frequency) support
Allow for handling of segments for coating and recoating
Allow for warping harnesses to adjust low order shape of
segment
– Inexpensive to design, build, install, adjust
– Zero maintenance for life of telescope
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SSA Concept
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Active Control
• Active control algorithm (details by G. Chanan)
– Same idea as Keck: edge sensors, actuators, least squares fitting
– Error propagation calculated to be acceptable: ~ 10x sensor noise
• Edge sensors
– Relative to Keck, want lower cost, avoid mechanical interlace
– New sensor design is still capacitive, but ~ on edges of segment
– Design by Mast and LBL engineering
• Actuators
– Relative to Keck, want lower cost, higher stroke
– Keck actuators used roller screw/hydro reducer (position actuator)
– TMT contract with Marjan to design and build a voice coil based force
actuator. This should have 4x stroke and be ~ 1/4 Keck cost
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Active Control Summary
Selected a = 0.6 m for segment size
Item
segment size
# segments
# edge sensors
# actuators
2005 December 8
Keck
0.9m
36
168
108
TMT
0.6m
738
4212
2214
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Principle of active control with edge sensors
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P1
Actuator (piston)
Sensor (measures height difference)
Sensor signal depends only on motion
of two neighbor segments
P2
P4
P3
P5
P7
P
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s  a1P1  a2 P2  a3 P3  a4P4  a5P5  a6P6
P8
P9
a are constant coefficients that depend only on geometry
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Keck Sensor Geometry
R = 35 m
Mirror Segment
7.5 cm
Sensor Mount
Sensor Body
Conducting
Surfaces
Sensor Paddle
2 mm
L
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title
Proposed TMT Sensor Geometry
Non-Interlocking Sensors
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Concept of segment support
Segment
Whiffle Tree
Reference Frame
Moving Frame
Mirror Cell
Truss
Actuator
Actuator
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Enclosures
Design options under study (from NIO)
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Adaptive Optics for TMT
• First generation
– NFIRAOS
• Near IR AO system with rms wavefront error ~ 190 nm. Generates
Strehl ratio ~ 0.7 at 2µm
• Hoping to upgrade to rms wavefront ~ 130 nm sometime after first light
• Large sky coverage (>50%)
• Na laser guide stars do atmospheric tomography
• Small field of view: 10”-1’
• Remember diffraction limit at 1µm is 0.007 arcsec
– MIRAO
• 5-25µm diffraction limited system
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Science Instruments
• Seeing limited instruments (studies underway)
– HROS: high resolution optical spectrometer- ~ HIRES
– WFOS: wide field optical spectrograph ~ LRIS, DEIMOS multi object
spectrometer, Fov ~ 20 arc min
• Diffraction limited instruments (studies underway)
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IRIS
MIRES
NIRES
WIRC
MOAO
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Construction Phase
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Approval to start ($$ available)
Primary mirror detail design review
Site Development FDR
Complete enclosure
Complete telescope installation
Begin segment installation
First light with 1/4 segments
All segments installed, phased
Begin TMT science
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Jan 2008
Apr 2008
Apr 2008
Feb 2012
Oct 2012
Aug 2012
Jul 2013
Apr 2014
Jan 2015
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Development phase
• Conceptual design review May 2006
• Cost review
Sept 2006
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TMT AO Development Program
• DDP program addresses TMT AO architecture, design and
technology development
• Key technologies and demonstrations
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MEMS
Lasers
Infrared tip-tilt wavefront sensing
Open loop control
Tomography
Wavefront sensor
Adaptive secondary technology
• AO development addressed by an $11.7M DDP plan
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• end
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TMT Experience with Adaptive Optics
UC Lick
CFHT
Gemini
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Palomar
Keck
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Adaptive Optics has come of age!
Ghez (UCLA) & collaborators
Gemini Hokupa’a/QUIRC image of
Galactic Center. Expanded view
shows IRS 13E & W in Kp
2005 December 8
40 x 40 arcsecond mosaic, colorcomposite NIRC2 image (at ~2.2 um)
of the Galactic Center using Keck Laser
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NGS / LGS Comparison
GC
NGS-AO best
June 2004 (4 nights)
46 best x (0.50x120)
SR=0.34, FWHM=92 mas
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LGS-AO
26 July 2004
8 x (0.25x120)
SR=0.75, FWHM=82 mas
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Keck AO Imaging of Uranus
Courtesy: L. Sromovsky
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Representative Construction Budget
Construction Phase ($800M)*
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2008
2009
2010
2011
2012
2013
2014
Possible NSF contribution
$50M
$100M
$160M
$180M
$140M
$100M
$70M
$12-25M
$25-50M
$40-80M
$45-90M
$35-70M
$25-50M
$18-35M
*Current range of estimates $600M-$800M
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CELT AO Approach
• We are exploring a staged AO implementation, to match
the evolving technology
• Each level change has a smaller wavefront error
• Each level change requires more and better deformable
mirrors
• Each level change requires more laser beacons
• Each level change delivers better image quality
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MCAO technology needs
Technolo
gy
Today
248 nm
180 nm
133 nm
Na guide star
lasers
2W CW dye,
8W micropulse/
macropulse
5 each with
Today’s
Technology
7 lasers,
15W m/m
pulsed
9 lasers, 15W
m/m pulsed,
AO on uplink
Deformable
mirrors
1 DM,
900 actuators
Visible WFS
detectors
128x128
x 1kHz
2 DMs,
2,500
actuators
5 each with
Today’s
3 each with
Today’s
3 DMs,
9,000
actuators
7 cameras,
256x256
x 1kHz
3 cameras,
5e- rms
4DMs,
21,000
actuators
9 cameras
256x256
x 1kHz
5 cameras,
5e- rms
Today’s
3x Today
10x Today
128x128 x
Near IR WFS 250Hz,
detectors
20e- rms read
noise
Real-time
1 x 109
operations/sec
computing
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TMT Reference Design
Following a detailed engineering study, the partnership has
agreed on a single basic reference design:
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30m filled aperture, highly segmented
aplanatic Gregorian (AG) two mirror telescope
f/1 primary
f/15 final focus
Field of view 20 arcmin
Elevation axis in front of the primary
Wavelength coverage 0.31 – 28 µm
Operational zenith angle range 1° thru 65°
Both seeing-limited and adaptive optics observing modes
First generation instrument requirements defined
AO system requirements defined
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