NIO GSMT Overview
VLOT/GSMT WORKSHOP
Victoria, BC
17 JULY, 2001
S. Strom, L. Stepp
AURA NIO: Mission
•
In response to AASC call for a GSMT, AURA
formed a New Initiatives Office (NIO)
–
•
collaborative effort between NOAO and Gemini to
explore design concepts for a GSMT
NIO mission
“ to ensure broad astronomy community access to a
30m telescope contemporary in time with ALMA and
NGST, by playing a key role in scientific and technical
studies leading to the creation of a GSMT.”
Goals of the NIO
•
•
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Foster community interaction on GSMT
Develop point design
Conduct studies of key technical issues and
relationship to science drivers
Optimize community resources:
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explore design options that yield cost savings,
emphasize studies that benefit multiple programs,
collaborate to ensure complementary efforts,
give preference to technologies that are extensible
to even more ambitious projects.
AURA New Initiatives Office
Management Board
Matt Mountain
Jeremy Mould
William Smith
Engineering Oversight
Jim Oschmann
Project Scientist
Steve Strom
Program Manager
Larry Stepp
Contracted studies
Systems Scientist
Brooke Gregory
Part time support
NOAO & Gemini**
Administrative Assistant
Jennifer Purcell
Opto-Mechanics
Myung Cho
Controls
George Angeli
Adaptive Optics
Ellerbroek/Rigaut
Mechanical Designer
Rick Robles
Structures
Paul Gillett
Site Testing
Alistair Walker
Instruments
Sam Barden
Comparative performance of a 30m
GSMT with a 6.5m NGST
10
R = 10,000
R = 1,000
R= 5
1
NGST advantage
S/N Gain (GSMT / NGST)
R 5
=
= ,0
R
1 0
R =
1 0
, 0
GSMT
advantage
Assuming a detected S/N of 10 for NGST on
a point source,
with
Comparative
performance
of a4x1000s
30m GSTM integration
with a 6.5m NGST
0.1
0.01
1E-3
1
10
Wavelength (microns)
GSMT/NGST at High Spectral Resolution
Molecular line spectroscopy S/N = 100
S/N Gain (GSMT / NGST)
10
R=10,000
R=30,000
R=100,000
1
4.6
12.3
0.1
17.0
0.01
1
10
Wavelength (microns)
Developing Science Cases
•
Two community workshops (1998-1999)
•
Tucson task group meetings (SEP 2000)
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NIO working groups (MAR 01 – SEP 01)
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NIO-funded community task groups (CY 2002)
NIO-funded community workshop (CY 2002)
– Broad participation; wide-ranging input
– Large-scale structure; galaxy assembly
– Stellar populations
– Star and planet formation
– Develop quantitative cases; simulations
– Define “Science Reference Mission”
KEY SCIENCE ENABLED BY GSMT
Najita et al (2000,2001)
Origin of structure in the universe:
from the big bang to planetary systems
Tomography of the Universe
•
•
•
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Goals:
Map out large scale structure for z > 3
Link emerging distribution of gas; galaxies to CMB
Measurements:
Spectra for 106 galaxies (R ~ 2000)
Spectra of 105 QSOs (R ~15000)
Key requirements:
20’ FOV; >1000 fibers
Time to complete study with GSMT: 3 years
Issues
– Refine understanding of sample size requirements
– Spectrograph design
Mass Tomography of the Universe
Existing Surveys + Sloan
Hints of Structure at z=3
(small area)
z~0.5
z~3
100Mpc (5Ox5O), 27AB mag (L* z=9), dense sampling
GSMT
1.5 yr
Gemini
50 yr
NGST
140 yr
Tomography of Galaxies and
Pre-Galactic Fragments
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•
•
•
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Goals:
Determine gas and stellar kinematics
Quantify SFR and chemical composition
Measurements:
Spectroscopy of H II complexes and underlying stars
Key requirements:
Deployable IFUs feeding R ~ 10000 spectrograph
Wide FOV to efficiently sample multiple systems
Time to complete study with GSMT: ~1 year
Issues
– Modeling surface brightness distribution
– Understanding optimal IFU ‘pixel’ size
Tomography of Individual Galaxies
out to z ~3
• Determine the gas and
stellar dynamics within
individual galaxies
• Quantify variations in
star formation rate
– Tool: IFU spectra
[R ~ 5,000 – 10,000]
GSMT 3 hour, 3s limit
at R=5,000
0.1”x0.1” IFU pixel
(sub-kpc scale structures)
J
26.5
H
25.5
K
24.0
Origins of Planetary Systems
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Goals:
•
Measurements:
•
Key requirements:
•
•
– Understand where and when planets form
– Infer planetary architectures via observation of ‘gaps’
Spectra of 103 accreting PMS stars (R~105; l ~ 5m)
On axis, high Strehl AO; low emissivity
Time to complete study with GSMT:
2 years
Issues
Understand efficacy of molecular ‘tracers’
Trades among emissivity; sites; telescope & AO design
Probing Planet Formation with High
Resolution Infrared Spectroscopy
Planet formation studies in the infrared (5-30µm):



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Probe forming planets in inner disk regions
Residual gas in cleared region
low t emission
Rotation separates disk radii in velocity
High spectral resolution
high spatial resolution
S/N=100, R=100,000, l>4mm
Gemini
GSMT
NGST
out to 0.2kpc sample ~ 10s
1.5kpc
~100s
X

8-10m telescopes with high resolution
(R~100,000) spectrographs can detect
the formation of Jupiter-mass planets in
disks around nearby stars (d~100pc).
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Stellar Populations
Goals:
Quantify IMF in different environments
Quantify ages; [Fe/H]; for stars in nearby galaxies
Develop understanding of galaxy assembly process
Measurements:
Spectra of ~ 105 stars in rich, forming clusters (R ~ 1000)
CMDs for selected areas in local group galaxies
Key requirements:
MCAO delivering 2’ FOV; MCAO-fed NIR spectrograph
Time to complete study with GSMT: 3 years
Issues
– MCAO performance in crowded fields
GSMT System Considerations
Science
Mission
- DRM’s
Instruments
Adaptive Optics
Active Optics
(aO)
Full System
Analysis
Site
Characteristics
Enclosure
protection
Support &
Fabrication
Issues
GSMT
Concept
(Phase A)
NIO Approach
Parallel efforts
– Address challenges common to all ELTs
• Wind-loading
• Adaptive optics
• Site
– Explore point design
• Start from a strawman
• Understand key technical issues
Enemies Common to all ELTs

Wind…..

The Atmosphere……
Wind Loading

Primary challenge may be wind buffeting
– More critical than for existing telescopes
• Structural resonances closer to peak wind power
• Wind may limit performance more than local seeing

Solutions include:
– Site selection for low wind speed
– Optimizing enclosure design
– Dynamic compensation
• Adaptive Optics
• Active structural damping
AVERAGE Pressure (C00030oo)
1.5
AVERAGE Pressure (C00030oo)
7
10
1
6
10
0.5
5
0
magnitude
pressure (N/m2)
10
-0.5
4
10
3
10
2
-1
10
-1.5
10
1
0
-2
0
50
100
150
200
Time History: time (second)
250
300
10
-3
10
SUM = -226
-2
-1
0
10
10
10
Frequency Response Function: frequency (Hz)
1
10
Animation
Wind pressure: C00030oo
test_2, day_2, Azimuth angle=00, Zenith angle=30, wind_gate:open, open; wind speed=11 m/s
Wind Pressure Structure Function
C00030oo
Average Structural Function for C00030oo
4
RMS pressure, Prms (N/m2)
3.5
3
2.5
2
1.5
1
0.5
0
Prms = 0.076124 d ** 0.4389
0
1000
2000
3000
4000
5000
sensor spacing, d (mm)
6000
7000
8000
How to scale to 30 meters:
RMS
pressure
differences
Average Structural Function for C00030oo
4
D(d) = 0.076 d 0.43
RMS pressure, Prms (N/m2)
3.5
3
2.5
2
1.5
1
0.5
0
Prms = 0.076124 d ** 0.4389
0
1000
2000
3000
4000
5000
sensor spacing, d (mm)
Spatial scale
6000
7000
8000
30M
The Gemini South wind test results
are available on the NIO Web site at:
www.aura-nio.noao.edu
AO Technology Constraints:
DMs and Computing power
(50m telescope; on axis)
Actuator pitch
r0(550 nm) = 10cm
S(550nm) S(1.65mm)
No. of
actuators
Computer
power
(Gflops)
CCD pixel
rate/sensor
(M pixel/s)
10cm
74%
97%
200,000
9 x 105
800
25cm
25%
86%
30,000
2 x 104
125
50cm
2%
SOR (achieved)
61%
8,000
789
1,500
~2
31
4 x 4.5
Early 21st Century technology will keep AO confined to l > 1.0 mm
for telescopes with D ~ 30m – 50m
AO Technology Constraints:
Guide stars and optical quality
MCAO system analysis by Rigaut & Ellerbroek (2000):
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30 m telescope
2 arcmin field
9 Sodium laser constellation 10 watts each
4 tip/tilt stars (1 x 17, 3 x 20 Rmag)
Telescope residual errors
~ 100 nm rms
Instrument residual errors ~ 70 nm rms
System performance:
l(mm)
1.25
1.65
2.20
Delivered Strehl
0.2 ~ 0.4
0.4 ~ 0.6
0.6 ~ 0.8
PSF variations < 1% across FOV
Site Evaluation
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ELT site evaluation more demanding
Evaluation criteria include
– surface and high altitude winds
– turbulence profiles
– transmission
– available clear nights (long-term averages)
– cirrus cover (artificial guide star performance)
– light pollution
– accessibility
– available local infrastructure
– land ownership issues
Site Evaluation

NIO gathering uniform data for sites in:
– Northern Chile
– Mexico and Southwest US
– Hawaii
Point Design: Philosophy
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Select plausible design that addresses key
science requirements
Identify key technical challenges
Focus analysis on key challenges
Evaluate strengths and weaknesses
– guide initial cost-performance evaluation
– inform concept design trades

Point design is only a strawman!
Point Design: Motivations

Provide a practical basis for wide-field, native
seeing-limited instruments
– science drivers strong

Explore a radio telescope approach
– possible structural advantages
• elevation bearing size comparable to primary
– possible advantages in accommodating large
instruments
Point Design: End-to End Approach
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Science Requirements (including instruments)
Error Budget
Control systems
Enclosure concept
– Interaction with site, telescope and budget
• Telescope structure
– Interaction with wind, optics and instruments
• Optics
•
– Interaction with telescope, aO/AO systems and instruments
AO/MCAO
– Interaction with telescope, optics, and instruments
• Instruments
– Interaction with AO and Observing Model
Derived Top Level Requirements
Narrow field AO
1 2
Field of View
10 arcsec + Principle wavelegths
1.0 - 2.5 microns
PSF
Resolution Diffraction limited + +
Stability
1%
+
Strehl
80%
Photom. accuracy(derived)
1%
Astrometric accuracy
10^-4 arcsec
+
Stability timescale
3,600 s
Emissivity
<20%
Maintenance/Ops
<15%
Reliability
90%
Science Efficiency
90%
3 MCAO
1 2 3 Low order AO
1 2 3 Seeing limited (PF) 1 2 3
+
2 arcmin + +
2 arcmin +
20 arcmin
1.0 - 2.5 microns
1.0 - 20 microns
0.4 - 2.5 microns
Diffraction limited +
5% - 50%
5% - +
10^-3 arcsec
3,600s
<20%
<15%
90%
90%
How to r ead this table:
Four telescope “Operating regimes” are defined and the specs for the
telesc ope (not the instrument) in each regime are cited. There are columns at
the right of each regime labeled 1,2,3 for the th ree science programs
discussed in the NO AO panel W orkshop. In these columns the spe cs are
assessed in term s of the adequacy for each sc ience program .
0.1-0.2 arcsec +
2%
<10%
2%
10^-2 arcsec
3,600s
10%
<15%
90%
90%
Matt:
0.4-0.7 arcsec +
2%
0%
1%
0.05 arcsec
10,000 s
15%
<15%
90%
90%
I think this mode is
important, its our only
"thermal IR" mode, and
we may find some
spectroscopy modes are
so photon starved they
1 Galaxy Evolution and LS Structure
2 Stellar Populations
3 Star and Planet Formation
Key:
+ meets needs
- does not meet needs
irrelevant or not critical
30m Giant Segmented Mirror Telescope
Point Design Concept
Typical 'raft', 7 mirrors per raft
GEMINI
1.152 m mirror
across flats
Special raft - 6 places, 4
mirrors per raft
30m F/1 primary, 2m adaptive secondary
Circle, 30m dia.
Key Point-Design Features

Paraboloidal primary
– Advantage: Good image quality over 20 arcmin
field with only 2 reflections
• Seeing-limited observations in visible
• Mid-IR
– Disadvantage: Higher segment fabrication cost
Key Point-Design Features

F/1 primary mirror
– Advantages:
• Reduces size of enclosure
• Reduces flexure of optical support structure
• Reduces counterweights required
– Disadvantages:
• Increased sensitivity to misalignment
• Increased asphericity of segments
Key Point-Design Features

Radio telescope structure
– Advantages:
• Cass focus can be located just behind M1
• Allows small secondary mirror – can be adaptive
• Allows MCAO system ahead of Nasmyth focus
– Disadvantage:
• Requires counterweight
• Sweeps out larger volume in enclosure
Controls Approach:
Offloading Decentralized Controllers
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
0.01
0.1
1
10
100
GSMT Control Concept
Deformable M2 : First
stage MCAO, wide field
seeing improvement
and M1 shape control
Active M1 (0.1 ~ 1Hz)
619 segments on 91 rafts
LGSs provide full sky
coverage
 M2: rather slow, large stroke
DM to compensate ground layer
and telescope figure,
or to use as single DM at
l>3 mm. (~8000 actuators)
 Dedicated, small field
(1-2’) MCAO system (~4-6DMs).
10-20’ field at
0.2-0.3” seeing
1-2’ field fed to the
MCAO module
Focal plane
Enabling Techniques
Active and Adaptive Optics
– Active Optics already integrated into Keck, VLT,
Gemini, Subaru, Magellan, …
– Adaptive Optics “added” to CFHT, Keck, Gemini,
VLT, …
Active and Adaptive Optics will have to be
integrated into GSMT Telescope and
Instrument concepts from the start
Enclosures
Design options under study
Response to Wind
Current concept will now go through “second iteration” of
design in response to wind analysis
Adaptive M2 Intrinsic to Point Design
Options: low- to high-order
• Compensate for winddriven M1 distortions
• Deliver high Strehl, mid-IR
images with low emissivity
• Deliver high-Strehl, near-IR
images
Goal: 8000 actuators
30cm spacing on M1
Key Point-Design Features

2m diameter adaptive secondary mirror
– Advantages:
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Correction of low-order M1 modes
Enhanced native seeing
Good performance in mid-IR
First stage in high-order AO system
– Disadvantages:
• Increased difficulty (i.e., cost)
Sky Coverage vs Wavelength; Strehl for an Adaptive M2
(single laser guide star; Rigaut, 2001)
GSMT Implementation Concept
- MCAO/AO foci and instruments
Oschmann et al (2001)
MCAO optics
moves with telescope
elevation axis
Narrow field AO or
narrow field seeing
limited port
MCAO Imager
at vertical
Nasmyth
4m
MCAO Near-IR Imager
(1:1 Unfolded)
40 mm
Pupil
~2 arc minute field
Instruments
•
•
Telescope, AO and instruments must be
developed as an integrated system
NIO team developing design concepts
– Prime focus wide-field MOS
– MCAO-fed near-IR MOS
– MCAO-fed near-IR imager
– AO-fed mid-IR HRS
– Wide-field deployable IFU spectrograph
•
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Build on extant concepts where possible
Define major design challenges
Identify needed technologies
Optical “seeing improvement”
using low order AO correction
Image profiles
are Lorenzian
16 consecutive nights of
adaptive optics the CFHT
Multi-Object Multi-Fiber Optical
Spectrograph (MOMFOS)
•20 arc-minute field
• 60-meter fiber cable
• 800 0.7” fibers
• 4 spectrographs, 200 fibers each
• VPH gratings
• Articulated collimator for different resolution regimes
Resolution
Example ranges with single grating
• R= 1,000
350nm – 650nm
• R= 5,000
470nm – 530nm
• R= 20,000
491nm – 508nm
• Detects 13% - 23% of photons hitting the 30m primary
Prime Focus MOMFOS
Barden et al (2001)
Key Point-Design Features

MOMFOS located at prime focus
– Advantages
• Fast focal ratio leads to reasonably-sized instrument
• Adaptive prime focus corrector allows enhanced seeing
performance
– Disadvantages
• Issues of interchange with M2
MOMFOS with Prime Focus Corrector
Conceptual design
fits in a 3m dia by
5m long cylinder
MOMFOS Spectrograph
R=20000
mode
R=5000
mode
R=1000
mode
500mm pupil; all spherical optics
350 nm
440 nm
500 nm
560 nm
650 nm
On-axis
Spot Diagrams for
Spectrograph
R=1000 case with 540 l/mm
grating.
470 nm
Circle is 85 microns equal to
size of imaged fiber.
On-axis
R=5000 case with 2250 l/mm
grating.
Barden et al (2001)
485 nm
500 nm
515 nm
530 nm
Key NIO Activities in 2001
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Core NIO team in place and working
Science case studies underway
Point design structural concept developed by SGH
Wind loading test data analyzed
AO system concept being developed
Instrument concepts
•
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•
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MCAO imager
MCAO NIR MOS
IFU spectrograph
Wide-field prime-focus MOS
High resolution mid-IR spectrograph
• Chilean site characteristics assembled
• Initial analysis of point design underway
Objectives: Next 2 years


Develop point design for GSMT & instruments
Develop key technical solutions
– Adaptive optics
– Active compensation of wind buffeting
– Mirror segment fabrication

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Investigate design-to-cost considerations
Involve the community in defining GSMT science and
engineering requirements
Involve the community in defining instrumentation
options; technology paths
Carry out conceptual design activities that support and
complement other efforts
Develop a formal partnership to build GSMT
Objectives: Next Decade
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Complete GSMT preliminary design (2Q 2005)
Complete final design (Q4 2007)
Serve as locus for
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community interaction with GSMT consortium
ongoing operations
defining; providing support capabilities
defining interactions with NGST
Key Milestones
2Q01: Establish initial science requirements
• 3Q01: Complete initial instrument concepts
• 3Q01: Complete initial point design analysis
• 2Q02: Identify key technology studies
• 1Q03: Fund technology studies
• 1Q03: Complete concept trade studies
• 2Q03: Develop MOUs with partner(s)
• 2Q03: Initiate Preliminary Design
• 4Q03: Complete SRM; establish science requirements
• 2Q05: Complete Preliminary Design
• 4Q05: Complete next stage proposal
Resources: 2001-2002
• NIO activities: $3.6M
– Support core NIO staff (‘skunk works team’)
–
–
• Analyze point design
• Develop instrument and subsystem concepts
Support Gemini and NOAO staff to
• Explore science and instrument requirements
• Develop systems engineering framework
Support community studies:
• Enable community efforts: science; instruments
• Enable key external engineering studies
• Support alternative concept studies
Resources: Next Decade
• $15M in CY 2003-2006 from NOAO base
– Enables start of Preliminary Design with partner
• $25M in CY 2007-2011 from NOAO base
• Create a ‘wedge’ of ~$10M/yr by 2010
– Enables NOAO funding of
• Major subsystem
• Instruments
• Operations