MAXAT-II
Woods Hole
17-18 September 1999
Overview
• Science Drivers
• Lessons of the past
• Focusing on Science and Innovation
Global context
Chile
8m
8m
4 x 8m
10 m
10 m
8m
Mauna Kea, Hawaii
Global context
2000
Keck I&II Keck-Inter.
ESO-VLTI
UT1,UT2,UT3,UT4
Gemini N&S
HET
LBT
2010
NGST
ALMA
VLA-upgrade
OWL
CELT
MAXAT
Phase A
2000
2008
2010
2015
Hubble Space Telescope moved the goal posts
Space
Ground
Detected
Signal
 Telescope Diameter .
Image Width

Sensitivity gains for a 21st Century telescope
For background or sky noise limited observations:
S
N

(Effective Collecting Area)1/2 .
Delivered Image Diameter 
6)1/2
S/N
x
(10
Detected
 Telescope Diameter .
Signal
Image Width

Adaptive Optics on 8m -10m Telescopes
Globular Cluster NGC6934
• V (0.55um) band
• FWHM of 0.6”
• K (2.2um) band
• ~120 exposures
totaling 23min
• FWHM of 0.09”
Gemini Optical Image
V-band
2.2um (K)
0.6 arcsec
Hokupa’a ON
Challenging 8m - 10m telescopes
Going beyond 0.1 arcsecond astronomy requires
resolution and sensitivity
Observations at z = 2 - 5
1 AU
1R
100 AU
Accretion Disks
Protoplanetary
Disks
1 - 10 milliarcseconds
0.1 pc
Molecular
Cloud
Cores
Jets/HH
10 pc
Mol. Outflows
Flux
AGN
Planets
Spectroscopy

Imaging
10 AU
Galactic observations out to
1kpc at 10 mas resolution
Stellar
Clusters
100 pc
GMC
Scientific Drivers for the “Next
Generation Groundbased Telescope”
• Maximize
Telescope Diameter .
Image Diameter 
• For diffraction limited
pixels
S/N  D2 /l
• In the detector limited
regime
S/N  D2
Detector technology (t)
What is the future of O/IR Groundbased Astronomy?
Facility
•
•
•
•
•
•
Gemini 8-M
HET
CHARA
LBT
Keck 1 & 2 +
VLTI +
Baseline (m) Collecting Area (m2)
8
9
354
100
165
200
2 x 50
60
5.5
100
157 + 11
201 + 20
What is the future of O/IR Groundbased Astronomy?
- technology enables innovation and, scientific discovery
Facility
•
•
•
•
•
•
•
•
•
Gemini 8-M
HET
CHARA
LBT
Keck 1 & 2 +
VLTI +
20 m
50-M Telescope
OWL
Baseline (m) Collecting Area (m2)
8
9
354
100
165
200
20
50
100
2 x 50
60
5.5
100
157 + 11
201 + 20
316
1950
7147
The Scientific Impact
- Modeled characteristics of 20m and 50m telescope
Assumed point source size (mas)
20M
(mas)
1.2mm 1.6mm 2.2mm 3.8mm 4.9mm 12mm 20mm
50M
(mas)
1.2mm 1.6mm 2.2mm 3.8mm 4.9mm 12mm 20mm
20
10
20
10
26
10
41
17
58
23
142
57
240
94
70%70%50%50%50%50%50%
Assumed detector characteristics
mm < l<5.5mm
Id
0.02 e/s
5.5mm < l<5mm
Nr
qe
Id
4e
80%
10 e/s
(Gillett & Mountain, 1998)
Nr
qe
30e
40%
The Scientific Impact
- Relative Gain of groundbased 20m and 50m telescopes compared to NGST
Imaging
Velocities ~30km/s
100
1
100
100
50M R=5
50m R=10,000
20m R=5
10
S/N Gain
20m R=10,000
10
10
1
0.01
0.01
1E-3
1E-3
10
W avelength ( m m )
1
0.1
0.1
1
10
1
1
0.1
10
100
0.1
0.01
0.01
1E-3
1E-3
1
10
W avelength ( m m )
Groundbased
advantage
10
NGST advantage
1
The impact of technology
Kitt Peak 4m c.1970
x 10 -100
Mass = 340 tonnes
Cost (1998) ~ $64M
scaled to 8m ~ $415M
Gemini 8m c.1998
Mass = 315 tonnes
Cost (1998) ~ $88M
Quantifying Innovation
- bypassing extrapolation
4m (KPNO)
Cost(1998) $61M
Cost “gain”
Image quality 1”
Performance “gain” (rel. to diff.)
8m (Gemini)
Scaled cost $415M
Actual cost $88M
x ~5
Image quality 0.1”
x5
“innovation factor” ~ 5 x 5 = 25
Changing the “paradigm”
- “extrapolation is innovations worst enemy”
NASA
HST
NGST
• Why ?
– Because the science drives us to this scale
– and because modern analytical and control systems
techniques allows us to reduce risk
End-to-End modeling works
Gemini Systems Review #2, March 1995
Arcseconds jitter
Area
Raw
Open
GEMINI
Optical
Design IMAGE - 8 weeks
0.065
0.065
Surface
into Errors
commissioning 0.201 0.187
Optical Alignment
0.014
0.014
Self Induced Seeing
0.027
0.027
Tip/tilt
sampling
=
100Hz
Open loop
Dynamic Alignment
0.147
0.036
Wind Shake
0.363
0.363
Meassurement Error
0
0
Off-Axis Error
0
0
Non-Linear Effects
3.658
0.636
RSS Totals
3.658
0.76
Autoguide
0.065
0.187
0.014
0.027
0.036
0.182
0
0
0.278
Tip/tilt
0.065
0.148
0.014
0.027
0.004
0.036
0.025
0.013
0.033
Focus
0.065
0.105
0.014
0.027
0.004
0.036
0.025
0.013
0.033
Active
0.065
0.046
0.014
0.027
0.004
0.036
0.025
0.013
0.033
0.389
0.169
0.139
0.102
Feb ‘99
• Telescope error budget,
50% e-e diameter (arcsecs) at 2.2mm
• System at 45 degrees, wind at 11 m/s, 200Hz
tip/tilt
sampling
Pointing
accuracy
with
• Error budget allocation is 0.100 at Zenith, active
0.0123
at 45ofdegrees
control
structure
Innovation Factors
Innovation factor
HST
NGST’
($2.4B)
($1B)
VLT
OWL
($100M)
Keck + LGS AO
($100M)
Gemini + MCAO
($100M)
($1B)
CELT
($400M)
50m
($1B)
50m
$600M
27 - 70
80
5
12
20
Baseline Approach
- ambitious at the outset
• Diffraction limited telescope D ~ 50m - 100m
• Operating wavelengths
Tech. challenge
0.9mm
-
3.8mm
Science challenge
• Operate over 90% of sky (airmass < 2.0)
• at full image quality over 75%
• Operate under 90% of site conditions
• at full performance under 75% of conditions
• Minimize risk -- if at all possible
• Focus on technologies that have the potential to produce the
most innovative results
• Multi-conjugate AO
• Smart structures
• Optical materials and support approaches
• Analytical analysis of wind-buffeting
• “Cheap” enclosures