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Giant Magellan Telescope Project
Science Drivers & AO Requirements
Patrick McCarthy - GMT Director
Phil Hinz & Michael Hart - GMT AO Team
AO4ELT - Paris 2009
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AO4ELT - June 22, 2009
The GMT Partners
US Institutions
Carnegie Institution
Harvard University
Smithsonian Institution
Texas A&M University
University of Arizona
University of Texas Austin
International Institutions
Astronomy Australia Limited
Australian National University
Korea Astronomy &
Space Science Institute
AO4ELT - Paris 2009
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The GMT Concept
Giant-Segmented
Mirror Telescope
10mas @ 1μm
380 sq. meters
f/8 Gregorian
Segmented Adaptive
Secondary
Natural Seeing 20 FOV
Ground-Layer
Correction 8 FOV
Diffraction-limited
20- 40 FOV
AO4ELT - Paris 2009
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Gregorian Instrument Mounting
Survey, GLAO, & Mid-IR instruments below
LTAO instruments above
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Instrument Platform Top Layout
AO relay
Natural seeing
instruments
AO instruments
GLAO/LGS
wavefront sensors
16 m
10 m
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Gregorian Instrument Rotator
Instrument
platform (IP)
Multiple
instrument
mounting
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GLAO & Mid-IR
Instruments
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Instrument Development
NIRMOS
GMTNIRS
GMACS
GMT Instrument Concepts
Mode
λ specification
(microns)
High resolution near-IR camera
LTAO
1.0-2.5
High contrast Mid-IR AO imager
NGSAO
1.2-2.5 & 3-5
Near-IR echelle spectrograph
AO & NS
0.9-5
High resolution optical spectrometer
NS
0.34-0.90
Wide-field multi-object near-IR spectrograph
GLAO
1.2-2.5
Wide-field multi-object optical spectrograph
NS
0.34-0.9
Near-IR integral field spectrometer
LTAO
1 – 2.5
Mode: AO = adaptive optics, NS = natural seeing
AO4ELT - Paris 2009
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AO Science Drivers
Exoplanet Studies
Imaging exoplanets in reflected light
Thermal radiation from young exoplanets
Structure of debris disks
Stellar Populations
IMF variations
Star Formation Histories
Black Hole Demographics
Galaxy Assembly
Structure & Dynamics of Galaxies at z > 2
First Light Studies
AO4ELT - Paris 2009
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Mid-IR Imaging of Exoplanets
L band detection limit 16x improved with ~4x larger
diameter
1 hour 5 sigma limits
HR8799 MMT
•
•
3.8 um: 25 Jy
3 λ/D: 0.48”
• Detect 5-10 MJ giant
10 um: 750 Jy
planets
3 λ/D: 1.0”
• 100-300 zody warm debris
disks
•
•
3.8 um: 1.5 Jy
3 λ/D: 0.11”
10 um: 45 Jy
3 λ/D: 0.25” •
•
Detect <1 MJ planets
3-10 zody warm debris
disks
GMT can undertake comprehensive study of giant
planets in > 3 AU range around stars at 30 pc.
AO4ELT - Paris 2009
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Nascent Planetary Systems
Pic at 11m
Gemini
JWST
GMT JWST
10 AU
GMT
ALMA
ELTs have the spatial resolution to probe the zone where Earth-like rocky planets live
AO4ELT - Paris 2009
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Resolving Distant Stellar Systems with AO
Globular Cluster around Cen A
HST
3.8Mpc
Gemini
3pc core radius
H-band
GMT
4mas pixels
2
Laser Tomography Adaptive Optics
AO4ELT - Paris 2009
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Resolving Distant Stellar Systems with AO
Globular Cluster around Cen A
Gemini
8m
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3.8Mpc
3pc core radius
H-band
GMT
25m
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UDF 6462, H-band, NIFS, Hα
z = 1.57, MB = -21.0, 5 hr object, 5 hr sky
HUDF - i
NIFS - Sum
Clump cluster
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UDF 6462, H-band, GMTIFS, Hα
z = 1.57, MB = -21.0, 5 hr object, 5 hr sky
HUDF - i
GMT - Sum
Clump cluster
AO4ELT - Paris 2009
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Image Sharpening with GLAO
Native Seeing
GLAO
15 x 15
60 mas
pixels
0.5 FWHM
0.15
The GMT architecture
is ideally suited for Ground-Layer
AOFWHM
AO4ELT - Paris 2009
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Adaptive Optics Prioritization
Three guiding considerations:
1. The AO system should allow us to meet our science goals
2. It should build on the natural strengths of the GMT
- low thermal IR foot print
- ground-layer conjugation with wide-field of view
- clean diffraction pattern
3. A clear upgrade path that uses much of the first generation
hardware
AO4ELT - Paris 2009
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AO Science Targets
Targets
Requirements
Exoplanets, debris disks,
AGN, black holes
Diffraction-limited images & IFU Spectra
small sizes, low sky density, no multiplexing
High Strehl, small field, low-background - Laser Tomography (LTAO) & NGS AO
z > 2 galaxies
Range of sampling scales, IFU & slit spectra
small sizes, moderate sky density
All-sky, range of Strehl, range of field, near-IR only - GLAO & LTAO
Resolved stellar populations
Diffraction-limited, emphasis on photometry
range of sizes, low sky density
All-sky, high Strehl, large field - LTAO & MCAO
AO4ELT - Paris 2009
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First Generation GMT AO Modes
Mode
Description
Laser tomography AO
(LTAO)
“All-sky” high Strehl - Sodium beacons
adaptive secondary is DM
Ground Layer AO
(GLAO)
“All sky” - Sodium beacons
factor of 2-4 image size reduction, 9′ FOV
Adaptive secondary conjugates to ground-layer
Natural Guide Star AO
(NGSAO)
High Strehl - natural guide stars within the
isoplanatic patch
Multi-Conjugate
~1′ diameter field, diffraction-limited, uniform PSF
12km conjugate DM in AO relay
Extreme AO
(ExAO)
High contrast, high Strehl for exoplanet detection
tweeter DM in instrument
AO4ELT - Paris 2009
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AO Features Unique to the GMT
•
ASM allows low background observations at > 2 µm.
•
•
•
For 25 m telescope, AO correction is needed even at 10
microns.
Exoplanet imaging and planet formation science drivers
are strengthened by this design choice.
ASM and wide-field telescope design enables GLAO.
•
•
Will increase the sensitivity and resolution of the planned
multi-object NIR and visible spectrographs for GMT.
Galaxy assembly and high-z science drivers are
strengthened by this design choice.
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System Performance
•
System is designed to maximize science return with
minimal technical development:
•
•
•
•
•
Adaptive Secondary Mirrors are near-replicas of LBT, VLT
design
Laser Guide Star system builds on Na laser development
for current telescopes.
Laser Projection system is similar to MMT design.
Expected AO performance is similar to MMT/LBT
systems.
Within the technical constraints above, the system
performance and design is derived from the science
requirements and the science instrument needs.
GCAR, Pasadena CA, April 27-29, 2009 -- AO system
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AO System Performance
Wavefront error source
RMS wavefront error (nm)
NGS
LTAO
ExAO
Primary mirror figure
20
20
15
Secondary mirror figure
20
20
15
Piston anisoplanatism (1 min calibration)
25
25
0
Piston errors from primary edge sensors
25
25
25
AO optical train (non-common path)
18
21
0
Science instrument
20
20
7
Fitting error
121
121
80
Atmospheric temporal lag
93
93
61
WFS measurement noise propagation
83
28
50
Reconstruction error
52
95
0
189
190
117
260 @13″
148 @ 1'
0
50
50
30
Total: On-axis
196
196
121
Total: Off-axis
325 @ 13″
246 @ 1′
High order total
Anisoplanatism error
Residual windshake
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AO System Performance
NGS performance versus guide
star brightness
SL’ = 90%
SK = 72%
SH = 56%
SJ = 36%
Wavelength (µm)
SM = 94%
K band Strehl Ratio
Strehl Ratio
AO System Performance versus wavelength
1 ms
2 ms
5 ms
10 ms
V magnitude (K5 star)
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AO4ELT - Paris 2009
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GMT 8.4m Off-Axis Prototype
The first GMT primary segment is in the
polishing/figuring stage
Completion date: March 2010
GMT
Segment #1
at the
Steward
Observatory
Mirror Lab
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Schedule
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GMT’s AO Top-Level Requirements Play to its Strengths:
Mid-IR with Adaptive Secondary
Wide-field Ground-Layer AO
Laser Tomography
Seeing-Limited Requirements and Instruments are also important…
High Dispersion Spectrographs
Wide-field Multi-Object Spectrographs
Astronomical Society of Australia Meeting - Perth July 08
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Backup Slides
Adaptive Optics Prioritization
GMT First Generation AO Modes:
- “all sky” laser tomography AO
high Strehl, 20 - 40 field of view, depending on 
- Ground layer adaptive optics
8 diameter field, factor of 2 - 4 improvement in FWHM, EE
- Natural guide star AO
high Strehl, small field of view, low thermal IR background
Upgrade modes:
MCAO (2nd DM in AO relay)
AO4ELT - Paris 2009
ExAO (2nd DM in instrument)
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Mid-IR Imaging of Exoplanets
L band detection limit 40x improved with ~3x larger
diameter
1 hour 5 sigma limits
3.8 um: 25 Jy
3 λ/D: 0.48”
10 um: 750 Jy
3 λ/D: 1.0”
Detect 5-10 MJ giant planets
100-300 zody warm debris
disks
3.8 um: 0.6 Jy
3 λ/D: 0.11”
10 um: 18 Jy
3 λ/D: 0.25”
Detect <1 MJ planets
3-10 zody warm debris disks
GMT can undertake comprehensive study of giant
planets in > 3 AU range around stars at 30 pc.
AO4ELT - Paris 2009
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AO Imaging of Young Planets
2/D at 1.5m
Angular Separation (mas)
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AO System Layout
LGS Projector
Adaptive secondary
mirror (ASM)
top view
Laser beam
relay
AO Focal Plane Assembly
(FPA)
• Optical relay
Laser house
• LGS wavefront sensors
• Phasing camera
• AO instruments
AO4ELT - Paris 2009
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AO System Overview
Laser
Projector
Adaptive
Secondary Mirror
(~4700 actuators)
top view
GLAO WFS
AO relay and
Narrow-field WFS
Laser
Housing
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Three independent measurements
Principal optical test
Scanning pentaprism test
Laser Tracker Plus
Full-aperture, interferometric test
Measures low-order aberrations
via slopes
Scans surface with laser tracker
Works on ground or polished surface
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Phase Apodization
1.65 m, 5% band. Diffraction only, no
wavefront error
10-6 suppression at 4 /D, 56 mas
AO4ELT - Paris 2009
10-5 companion
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AO Imaging of Massive Planets
3/D at 1m
Angular Separation (mas)
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AO Studies of Black Hole Demographics
1.22/D
@1.5m
8m
GMT
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AO Imaging of Young Planets
2/D at 5m
Angular Separation (mas)
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