Download Progress on the 30m Giant Segmented Mirror

Progress on the 30m Giant
Segmented Mirror Telescope
AURA New Initiatives Office
Leiden, 17 May 2001
Matt Mountain
Jim Oschmann
Knut Olsen
1
GSMT
• Partnership between Gemini, NOAO and our
communities
• Science Enabled
• Implementation Concepts
• Resources
• Interfaces
• Issues
2
Science & Instrument workshops





Madison MAXAT science - 1998
Woods Hole MAXAT technology -1999
Tucson MAXAT instruments -2000
Tucson GSMT science – 2000
Subsystem working group meetings 19992000


Systems, optics, structures…
OPTICON, Edinburgh, Leiden
3
GSMT System Considerations
- Astronomers View
Science
Mission
- DRM’s
Instruments
Adaptive Optics
Active Optics
(aO)
Full System
Analysis
Site
Characteristics
Enclosure
protection
Support &
Fabrication
Issues
GSMT
Concept
(Phase A)
4
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
+
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” ar e defined and the specs f or the
telesc ope (not the instr ument) in each regime are cited. There are columns at
the right of each regime labeled 1,2,3 for the th ree science pr ograms
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
5
30m Giant Segmented Mirror
Telescope concept
GEMINI
Typical 'raft', 7 mirrors per raft
1.152 m mirror
across flats
Special raft - 6 places, 4
mirrors per raft
Circle, 30m dia.
30m F/1 primary, 2m adaptive secondary
6
The Enemies…..
• Wind…..
• The Atmosphere……
7
Enabling techniques
• Active and Adaptive Optics
• Active Optics already integrated into Keck,
VLT and Gemini
• Adaptive Optics “added” to Keck, Gemini (and
soon) VLT
 Active and Adaptive Optics will have to be
integrated into GSMT Telescope and
Instrument concepts from the start
8
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
>3 m. (~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
9
AO Technology constraints (50m telescope)
Actuator pitch
r0(550 nm) = 10cm
S(550nm) S(1.65m)
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  > 1.0 m
for telescopes with D ~ 30m – 50m
10
MCAO on a 30m: summary
• MCAO on 30m telescopes should be used  > 1.25 m
• Field of View should be < 3.0 arcminutes,
(m)
1.25
1.65
2.20
Delivered Strehl
0.2 ~ 0.4
0.4 ~ 0.6
0.6 ~ 0.8
Rigaut & Ellerbroek (2000)
9 Sodium laser constellation
4 tip/tilt stars (1 x 17, 3 x 20 Rmag)
PSF variations < 1% across FOV
• Assumes the telescope residual errors ~ 100 nm rms
• Assumes instrument residual errors ~ 70 nm rms
– Equivalent Strehl from focal plane to detector/slit/IFU > 0.8 @ 1 micron
– Instruments must have:
• very high optical quality
• very low internal flexure
11
AO an integral part of the
GSMT Concept
• Low order correction for wind buffeting and
“seeing improvement”
– 3 Natural Guide stars give full sky coverage
• Narrow Field AO requires at least one LGS for
<5m
– Science requires low emissivity implementation
• MCAO requires multiple NGS and multiple
DM’s
12
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,
withof4x1000s
integration
Comparative
performance
a 30m GSTM
with a 6.5m NGST
0.1
0.01
1E-3
1
10
Wavelength (microns)
13
Comparative performance of a 30m
GSMT with a 6.5m NGST 100 m
10
R = 10,000
R =R1,000
=5
R= 5
OWL
1
NGST advantage
S/N Gain (GSMT / NGST)
R 5
=
= ,0
R
1 0
R =
1 0
, 0
advantage
Assuming a detected S/N of 10 for NGST on
a point source,
withof4x1000s
integration
Comparative
performance
a 30m GSTM
with a 6.5m NGST
0.1
0.01
1E-3
1
e = 15%
10
Wavelength (microns)
14
GSMT Implementation concept
- wide field (1 of 2)
Barden et al (2001)
15
Optical “seeing improvement” using
low order AO correction
Image profiles
are Lorenzian
16 consecutive nights of
adaptive optics the CFHT
16
GSMT Implementation concept
- wide field (2 of 2)
1m
20 arc minute MOS
on a 30m GSMT
• 800 0.75” fibers
• R=1,000
350nm – 650nm
• R=5,000
470nm – 530nm
• Detects 13% - 23%
photons hitting 30m
primary
Barden et al (2001)
17
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
18
Spot diagrams for MCAO + Imager
Diffraction limited performance for 1.2m – 2.2 m can be achieved
19
MCAO Optimized Spectrometer
• Baseline design stems from current GIRMOS d-IFU tech study
occurring at ATC and AAO
– ~2 arcmin deployment field
– 1 - 2.5 µm coverage using 6 detectors
• IFUs
– 12 IFUs total ~1.5”x1.5” field
– ~0.05” spatial sampling R ~ 6000 (spectroscopic OH suppression)
20
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
21
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
22
High resolution, high Signal/Noise
observations
Molecular line spectroscopy S/N = 100
S/N Gain (GSMT / NGST)
10
R=10,000
R=30,000
R=100,000
Detecting the molecular gas from gaps swept
out by a Jupiter mass protoplanet, 1 AU
from a 1 MO young star in Orion (500pc)
(Carr & Najita 1998)
1
4.6
12.3
0.1
17.0
0.01
1
10
Wavelength (microns)
GSMT observation ~ 40 mins
(30 mas beam)
23
GSMT will need an Adaptive Secondary
30cm actuator pitch
Good conditions (0.5" seeing):
lambda diameter["] %energy
1.25000 0.0226732 0.338447
1.60000 0.0290217 0.473207
2.25000 0.0408118 0.613434
3.8
0.71
5.00000 0.0906928 0.758112
10.0000 0.181386 0.789314
20.0000 0.362771 0.797315
8,960 actuators, 30cm spacing on Primary
3,225 actuators, 50cm spacing
50cm actuator pitch
Good conditions (0.5" seeing):
lambda diameter["] %energy
1.25000 0.0226732 0.251838
1.60000 0.0290217 0.395080
2.25000 0.0408118 0.559923
3.8
0.66
5.00000 0.0906928 0.744220
10.0000 0.181386 0.785671
20.0000 0.362771 0.796393
24
Sky coverage and
Strehl for narrow field,
thermal infrared
observations using an
adaptive secondary
(wind buffeting on M1)
(Rigaut, 2001)
 for  < 10m single
laser beacon required
25
End-to-End Approach
• Science Requirements (including instruments)
• Error Budget
• 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
• Observing Model
26
Wind Loading
• Driving characteristic may be wind
– Lower wind sites with good seeing
– How to protect telescope
•
•
•
•
Enclosure needs
May be more limiting than local seeing to performance
Cost drivers
Advance methods for correcting
More critical than for existing telescopes
27
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
1
10
10
10
Frequency Response Function: frequency (Hz)
10
28
Average pressure PSD DATA
- effect of enclosure shutters
29
average pressure PSD by EL
 Note: No elevation dependence on average pressure on primary
30
How to scale to 30 meters:
Average pressure SF (C00030oo)
RMS
pressure
differences
Average Structural Function for C00030oo
4
D(d) = 0.096 d 0.41
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
Spatial scale
30M
31
An enclosure is essential: scaled up and
taller variation of JCMT Enclosure
32
30m Giant Segmented Mirror
Telescope concept
Z
X
Y
Output Set: Mode 1, 2.156537 Hz, Deformed(0.0673): Total Translation
Horizon Pointing - Mode 1 = 2.16 Hz
33
Response to Wind
Current concept will now go through “second iteration” of design
In response to wind analysis
34
Point Design
Initial Analysis
• Finite element model of structure
– Gravity sag and initial modal analysis
• Wind PSD’s calculated from Gemini tests
– To be applied to current model
• Structure function approach to scaling Gemini
data on wind buffeting to 30 meter
– Preparing to apply wind buffeting to point design
• Aid in systems flow down of requirements
• Early trades possible soon
35
Objectives: Next 2 years
• Develop point design for GSMT & instruments
– Carried out within NIO
• Attack key technical problems
– Adaptive optics
– Wind loading
– Mirror segment fabrication
• Continue community involvement in defining:
– Science & technical requirements
– Instrumentation options; technology paths
• Support design studies that complement other projects
(CELT, FELT, OWL, etc.)
36
Resources: Next 2 years
• Combined Gemini partnership + NOAO resources: $2.1M
• Core NIO effort focused on studies to:
•
– Analyze point design
– Attack key technical issues
– Develop instrument and subsystem concepts
– Explore science and instrument requirements
Additional US National efforts: $2.0M external studies:
– Enable community efforts: science; instruments
+ Study contracts
+ Broad community workshops
– Enable key external engineering studies; alternate concepts
+ End-to-end system model + detailed error budget
+ Alternate system design concept studies
+ Alternate AO system design and modeling studies
+ Develop site testing equipment; apply in Chile
37
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
TBD
Administrative assistant
Jennifer Purcell
Systems Scientist
Brooke Gregory
Part time support
NOAO & Gemini
Adaptive Optics
Francois Rigaut (Gemini)
Optics
Larry Stepp
Controls
George Angeli (NOAO)
Adaptive Optics
Brent Ellerbroek (Gemini)
Mechanical Designer
Rick Robles
Structures
Paul Gillett
Site Testing
Alistair Walker (NOAO)
Instruments
Sam Barden (NOAO)
38
GSMT STEERING COMMITTEE
Present Members
John Casani
Alan Dressler
Richard Ellis
Bob Fugate
Jay Gallager
Bob Gehrz
Riccardo Giovanelli
Bob Kirshner
Rolf Kudritzki
Simon Lilly
Joe Miller
Jerry Nelson
Larry Ramsey
Chuck Steidel
Jet Propulsion Laboratory
Carnegie Observatory
CalTech
Starfire Optical Range
University of Wisconsin
University of Minnesota
Cornell University
Harvard-Smithsonian, CfA
University of Hawaii
HIA
University of California
University of California
Penn State University
CalTech
39
Interfaces
• Community task groups; workshops
• NSF, other Gemini Agencies (PPARC, NRC,
ARC..)
• Potential partners: CELT; ESO; others
• Other next generation telescope projects
• Private sector/government lab consultants
• NIO steering committee
• US System steering group
– GSMT is the apex of US system
– System must support GSMT
• OPTICON
40