WMKO Next Generation Adaptive Optics
Science Advisory Team:
Introductions & NSAT Charge
Taft Armandroff, Mike Bolte,
Shri Kulkarni, Hilton Lewis
June 11, 2009
Introductions
• NSAT Members:
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–
–
–
–
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Laird Close
George Djorgovski
Richard Ellis
James Graham
Michael Liu
Keith Matthews
Mark Morris (chair)
Tomasso Treu
• Directors
• NGAO Team
2
217 refereed science papers (thru May/09)
30
Number of Papers (per year)
Interferometer
25
LGS
NGS
20
10%
26%
64%
15
10
5
0
2000
2001
2002
2003
2004
2005
2006
2007
Number of Refereed Publications
Keck AO Science Product
25
Solar System
20
Galactic
Extra-galactic
29%
52%
19%
15
10
5
0
2000 2001 2002 2003 2004 2005 2006 2007 2008
Year
2008
Year
Area
Galactic
Extragalactic
Solar
System
Sub-Topic
Brown dwarfs & low mass stars
Galactic Center
Compact objects
Star formation
High redshift galaxies
Gravitational lensing
Stellar populations
Supernovae
Kuiper Belt
Asteroids
Number of
Papers
15
10
2
1
11
5
3
5
4
1
M. Liu
3
Keck LGS AO Science
Galactic Center
KBO’s
Bipolar
Jet
Methane brown dwarfs
4
Jan-15
Jan-14
Jan-13
Jan-12
Jan-11
K2 NGAO + Camera
K2 Center Launch
K1 LGS + OSIRIS +
Interferometer
K1&2 WFC Upgrade
K2 OSIRIS
K2 LGS
1
Jan-10
Jan-09
Jan-08
Jan-07
Jan-06
Jan-05
Jan-04
Jan-03
K2 NIRC2
K1&2 NGS Interferometer
Jan-02
K2 NGS
K2 NIRSPAO
0
Jan-01
Jan-00
Jan-99
Keck AO Science Capabilities
Keck AO First TAC-allocated Science Milestones
Future
Date
5
NGAO Project Milestones & Funding
• All of the following successfully completed:
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–
–
–
Jun/06.
Apr/08.
Nov/08.
Mar/09.
Proposal submitted
System Design Review
TMT AO cost comparison
Build-to-cost concept review
• Preliminary Design Review planned for Apr/10
• TSIP provided $2M for the preliminary design
• ATI (Nov/08) & MRI (Jan/09) proposals submitted for
NGAO related activities
• Private funding being sought
• MRI-R2 & TSIP proposals will be submitted this year
6
NGAO System Design Review (April/08)
Very Experienced Review Committee:
• Brent Ellerbroek & Gary Sanders (TMT)
• Bob Fugate (NMT) & Norbert Hubin (ESO)
• Andrea Ghez (UCLA) & Nick Scoville (Caltech)
•
•
•
“The review panel believes that Keck Observatory has assembled an
NGAO team with the necessary past experience … needed to develop
the NGAO facility for Keck. It is a sound, though aggressive, strategy
to be among the first observatories to develop and depend on
advanced LGS AO systems as a means to maintain Keck’s leadership
in ground-based observational astronomy for the immediate future.“
“The panel also believes that NGAO is an important pathfinder for the
2nd generation of AO based instruments for future ELT’s”
“The NGAO Science cases are mature, well developed and provide
high confidence that the science … will be unique within the current
landscape.”
7
NGAO Build-to-Cost Review (March/09)
Very Experienced Review Committee:
• Brent Ellerbroek (TMT)
• Michael Liu (U. Hawaii)
• Jerry Nelson (TMT, UCSC)
•
•
Cost cap with instruments & contingency: $60M then-year dollars
"The Committee strongly congratulates the NGAO team for a concise,
convincing presentation which demonstrates that the above criteria for
further development of the system have been very effectively met. We
recommend that the project is now ready to proceed with the
Preliminary Design Phase to continue the development of the updated
system concept, with no further changes in overall scope or basic
architecture either necessary or desirable."
8
NSAT Charter
•
•
•
•
The purpose of the NSAT is to help ensure that the NGAO facility will
provide the maximum possible science return for the investment and
that NGAO will meet the scientific needs of the Keck community.
To that end the NSAT will provide science advice to the NGAO project
with an emphasis on the further development of the science cases and
science requirements.
The NSAT is also expected to provide science input in such areas as
performance requirements, operations design, and design trades.
The NSAT will report to the Directors, providing a panel of experts for
them to consult, and will work closely with the NGAO Project Scientist
providing an expert science team that represents a wide range of AO
interests in the Keck community.
9
NSAT Responsibilities
for the Preliminary Design
Collaborate with the NGAO project scientist and project team to:
•
•
•
•
•
•
Further develop the NGAO science cases and science case requirements.
Evaluate the scientific performance of the NGAO design on various science
cases (for example, PSFs reflecting the modeled NGAO performance may be
provided for evaluation).
Determine what science cases and requirements should drive a phased
implementation of NGAO and the scientific impact of a phase implementation.
Support funding efforts by contributing to the science portion of proposals
and/or making presentations.
Determine optimal observing and operations strategies including further
development of science case observing scenarios and providing input to the
Operations Concept Document and the design of the observing tools.
Ensure that NGAO is scientifically competitive by providing input on NGAO’s
science competitiveness and complementarity with respect to other facilities.
10
NSAT Responsibilities
for the Preliminary Design
Collaborate with the NGAO project scientist and project team to:
•
•
•
•
Ensure that the broader Keck community’s input is taken into account in the
development of the NGAO Preliminary Design by liaising with the broader
community.
Promote NGAO in the Keck, national and international communities.
Ensure that technical (e.g., design and performance) trades made by the
NGAO project have adequate science input by evaluating the science impact
of proposed changes.
Prepare and present the NGAO science issues and broader perspective to the
Directors and SSC.
11
NSAT Longer Term Role
•
The NSAT role and responsibilities in the remaining phases of the
NGAO project will be assessed towards the end of the Preliminary
Design phase. The Directors will seek input from the NSAT and
NGAO project in defining the NSAT’s longer term role.
12
WMKO Next Generation Adaptive
Optics Introduction for the NSAT
Peter Wizinowich, Sean Adkins, Rich Dekany,
Don Gavel, Claire Max, Elizabeth McGrath
& the NGAO Team
June 11, 2009
Presentation Sequence
•
•
•
•
•
Brief Overview
Science Priorities
Design & Performance
Science Instruments
How can the NSAT help?
14
Overview
NGAO - Next Generation AO
Key Science Goals
Understanding the Formation and Evolution of Today’s Galaxies
Measuring Dark Matter in our Galaxy and Beyond
Testing the Theory of General Relativity in the Galactic Center
Understanding the Formation of Planetary Systems around Nearby Stars
Exploring the Origins of Our Solar System
Key New Science Capabilities
Near Diffraction-Limited in Near-IR (K-Strehl ~80%)
AO correction at Red Wavelengths (0.65-1.0 m)
Increased Sky Coverage
Improved Angular Resolution, Sensitivity and Contrast
Improved Photometric and Astrometric Accuracy
Imaging and Integral Field Spectroscopy
16
How is NGAO different from Keck’s AO
today?
17
NGAO System Architecture
Key Features:
1. Fixed narrow field laser tomography
2. AO corrected NIR TT sensors
3. Cooled AO enclosure smaller
4. Cascaded relay
5. Combined imager/IFU instrument
18
Project Milestones
Year Month
NGAO Project Milestone
2006 June NGAO Proposal to SSC - complete
2006 Oct. System Design Start - complete
2008 April System Design Review - complete
2009 March Build-to-Cost Review - complete
2009 Dec. Laser Preliminary Design Reviews
2010 April Preliminary Design Review
2011 April Laser Final Design Review
2011 Sept. Keck II Center Launch Telescope Operational
2012 April Detailed Design Review
2013 Oct. Pre-Lab I&T Readiness Review
2013 April Pre-Ship Readiness Review
2014
July NGS AO First Light
2014 Sept. LGS AO First Light
2014 Oct. 15A Shared-Risk Science Availability Review
2015 Feb. Operational Readiness Review
19
Cost Estimate in Then-Year $k
NGAO System
System Design
Preliminary Design
Detailed Design
Full Scale Development
Delivery & Commissioning
Contingency (24%)
NGAO Total =
Actuals ($k)
Plan (Then-Year $k)
FY07 FY08 FY09 FY10 FY11 FY12 FY13
739
495
214
1240
1492
1600
5500
978
400
500
7415
8715
739
NGAO Instrument(s)
FY07
IFS Design
Imager and IFS Instrument
Contingency (10/30%)
NGAO Instrument Total =
Overall Total =
739
709
FY08
709
1240
466
3958
1741
3014
6000 10134 11729
FY09 FY10 FY11 FY12 FY13
51
229
78
123
443
4284
4264
486
17
67
1309
1279
146
192
739
5670
5544
632
1432
4697 11670 15678 12361
FY14
5262
1764
3119
10145
FY14
FY15
1825
611
2436
FY15
Total
1234
2946
8078
22293
3589
8951
47090
12
4
15
0
Total
358
9613
2822
12793
10161
2436
59883
In FY09 $: $42M for NGAO, $12M for Instrument(s)  $54M total
20
Science Priorities
We categorized science cases into 2 classes
1. Key Science Drivers:
– These push the limits of AO system, instrument, and
telescope performance. Determine the most difficult
performance requirements.
2. Science Drivers:
– These are less technically demanding but still place
important requirements on available observing
modes, instruments, and PSF knowledge.
22
“Key Science Drivers”
(in inverse order of distance)
1.
High-redshift galaxies
2.
Black hole masses in nearby AGNs
3.
General Relativity at the Galactic Center
4.
Planets around low-mass stars
5.
Asteroid companions
23
“Science Drivers”
(in inverse order of distance)
1.
Gravitationally lensed galaxies
2.
QSO host galaxies
3.
Resolved stellar populations in crowded fields
4.
Astrometry science (variety of cases)
5.
Debris Disks and Young Stellar Objects
6.
Giant Planets and their moons
7.
Asteroid size, shape, composition
24
Key Science Requirements:
1. Assembly and star formation history of high z galaxies
• “High Redshift Galaxies” has very wide scope
– z > 6:
Finding and characterizing galaxies
– 3 < z < 6: Morphologies, colors
– 1 < z < 3: Internal kinematics, structure at time of peak star formation
and merging
• To define “Key Science Driver”
we focused on 1 < z < 3
– 1 < z < 3 epoch: spatial resolution of
10-m telescope has strong impact
• Prominent emission lines redshifted
to J, H, K bands
• Sufficient signal-to-noise to spatially
resolve internal kinematics, star
formation rates, metallicity gradients
using spatially resolved spectroscopy
25
25
Cooled AO system for better performance at K-band
•
Target goal: AO to contribute at most 30% (sky + tel) background
•
This opens “typical” z~2.6 galaxies within reasonable observing
times ~ 3 hours
•
We have to assess how much it’s worth investing to cool NGAO at
K band, in view of JWST’s great advantage in sensitivity
26
Key Science Requirements:
2. Black hole masses in nearby galaxies
• M-s relation: black hole mass
closely correlated with velocity
dispersion of stars
Simulation: 108 Msun BH at 20 Mpc,
inclination 60 deg to line of sight
• Spatial resolution: need to
resolve the black hole's
dynamical sphere of influence
rg = GMBH/s2
• If you see the Keplerian rise in
the rotation curve, mass
determination becomes more
accurate
27
Addition of optical bands:
advantage for BH mass determination
• With NGAO, diffraction-limited PSF
core at Ca II triplet is major
improvement in spatial resolution
– Enables many more low-mass
black holes to be detected
– Better for resolving rg in nearby
galaxies, leading to more
accurate measurements
– NGAO I-band can study highmass distant galaxies to pin
down extreme end of M-s
relation
Minimum BH mass detectable vs.
distance, assuming local M- s relation
and  2 resolution elements across rg
28
Key Science Requirements:
3. General relativistic effects in the Galactic Center
• Measure General Relativistic prograde precession of stellar
orbits in Galactic Center
• Requires astrometric precision of 100 as (now 170 as)
and radial velocity precision to 10 km/sec (now 17 km/sec)
• Imaging field 10 x 10 arc sec
• Near IR IFU spectra,
R ≥ 4000, FOV ≥ 1” x 1”, need
IR ADC
Need to evaluate optimal
spectral resolution
Credit: UCLA Galactic Center Group
29
Galactic Center: possibility of detecting
general relativistic effects near black hole
• Use orbits of star(s)
that pass very close to
black hole
• Example: general
relativistic precession
• SNR > 10 requires
astrometric precision
better than 0.1 mas
• Current astrometric
precision of 170 as is
only achieved for
bright stars like S0-2.
Assumes radial velocity measurement errors of 10 km/s
30
Key Science Requirements:
4. Planetary & brown dwarf companions to low mass stars
• Faintness of low-mass stars, brown dwarfs,
and the youngest stars make them
excellent NGAO targets
• Small imaging field ≤ 5 arc sec
• Relative photometry to 5%, astrometry to
PSF FWHM/10, contrast H = 13 at 1”
• Instruments:
– Imaging 0.9 - 2.4 microns
– Single near IR IFU spectroscopy, still need
to specify spectral resolution
• Observing modes: coronagraph needed
31
Contrast Requirements for Planets Around
Low-Mass Stars
• Need to reach at least H=10 at 0.2” for our
primary target sample (planets around nearby
old field brown dwarfs).
• We plan to simulate achievable contrast ratio
using reasonable coronagraph +
NGAO PSF models
• Preliminary simulations from SDR
indicate a simple coronagraph
with a 6l/D spot size may be
sufficient for most science cases.
Giant planet (2x mass
of Jupiter)
Brown dwarf
1/30 mass of Sun
(hidden behind
occulting mask)
Simulations by Bruce Macintosh and
Chris Neyman
32
Key science requirements:
5. Multiplicity, size, shape of minor planets
• Minor planet formation history and interiors
by accurate measurements of size, shape,
companions
• Small, on-axis imaging field ( ≤ 3 arc sec)
• Relative photometry to 5%, astrometry ≤ 5
mas, wavefront error ≤ 170 nm, contrast H
 5.5 at 0.5 arc sec
• Instruments:
– Imaging: visible and near-IR
– Near IR IFU spectroscopy: 1.5 arc sec field;
still need to specify spectral resolution
• Observing modes: non-sidereal tracking,
<10 minute overhead switching between
targets
Nix and Hydra
Credit: D. Tholen
Asteroid Sylvia
and moons
33
Science
Requirements &
Performance
Budget Process
34
34
Science Priority Input: SDR Report
•
“The NGAO Science cases are mature, well developed and provide enough
confidence that the science … will be unique within the current landscape.”
•
“The science requirements are comprehensive, and sufficiently analyzed to
properly flow-down technical requirements.”
•
“… high Strehl ratio (or high Ensquared Energy), high sky coverage, moderate
multiplex gain, PSF stability accuracy and PSF knowledge accuracy … These
design drivers are well justified by the key science cases which themselves fit
well into the scientific landscape.”
•
The panel was concerned about complexity & especially the deployable IFS
•
–
“However, the review panel believes that the actual cost/complexity to science
benefits of the required IFS multiplex factor of 6 should be reassessed.”
–
“… recommends that the NGAO team reassess the concept choices with a goal to
reduce the complexity and risk of NGAO while keeping the science objectives.”
The panel had input on the priorities
–
“The predicted Sky Coverage for NGAO is essential and should remain a top
requirement.”
35
Science Priority Input: Keck Scientific Strategic Plan
•
“NGAO was the unanimous highest priority of the Planetary, Galactic, &
Extragalactic (high angular resolution) science groups.
•
“NGAO will reinvent Keck and place us decisively in the lead in highresolution astronomy. However, the timely design, fabrication & deployment
of NGAO are essential to maximize the scientific opportunity.”
•
“Given the cost and complexity of the multi-object deployable IFU instrument
for NGAO, …, the multi-IFU instrument should be the lowest priority part of
the NGAO plan.”
•
Planetary recommendations in priority order: higher contrast near-IR
imaging, extension to optical, large sky coverage.
•
Galactic recommendations in priority order: higher Strehl, wider field, more
uniform Strehl, astrometric capability, wide field IFU, optical AO
•
Extragalactic high angular resolution recommendations: a balance between
the highest possible angular resolution (high priority) & high sensitivity
36
Science Implications of no Multiplexed d-IFU
• As a result of our Build-to-Cost approach, we have eliminated the
multiplexed d-IFU.
– Reduces complexity and decreases risk of overall NGAO system
– Available laser power can be utilized to provide excellent performance
for science targets over narrow fields (<40”)
Science implications:
• Galaxy Assembly and Star Formation History
– Reduced observing efficiency (from 6x to 1x)
– Slightly increased performance for single, on-axis target
– Decreased overall statistics for understanding galaxy evolution. We will
need to carefully select sub-categories of high-z galaxies to focus on.
• General Relativity in the Galactic Center
– Decreased efficiency in radial velocity measurements (fewer stars
observed simultaneously)
– Can gain back some of this with a single IFU with a larger FOV.
37
Flowdown of Science Priorities
(resultant NGAO Perspective)
Based on the SDR science cases, SDR panel report & Keck Strategic Plan:
1. High Strehl
•
•
Required directly, plus to achieve high contrast NIR imaging, shorter l AO, highest
possible angular resolution, high throughput NIR IFU & high SNR
Required for AGN, GC, exoplanet & minor planet key science cases
2. NIR Imager with low wavefront error, high sensitivity, ≥ 20” FOV & simple
coronagraph
•
Required for all key science cases.
3. Large sky coverage
•
Priority for all key science cases.
4. NIR IFU with high angular resolution, high sensitivity & larger format
•
Required for galaxy assembly, AGN, GC & minor planet key science cases
5. Visible imaging capability to ~ 800 nm
•
Required for higher angular resolution science
6. Visible IFU capability to ~ 800 nm
7. Visible imager & IFU to shorter l
8. Deployable multi-IFS instrument (removed from plan)
–
Included
Excluded
Ranked as low priority by Keck SSP 2008 & represents a significant cost
38
Performance vs Science Requirements
Key Science Driver
SCRD Requirement
Performance of B2C
EE  50% in 70 mas for
sky cov = 30% (JHK)
EE > 70% in 70 mas for
sky cov  90% (K band)
√
Nearby AGNs
(Z band for Ca triplet)
EE  50% in 1/2 grav
sphere of influence
EE  25% in 33 mas 
MBH  107 Msun @ Virgo
cluster (17.6 Mpc )
√
General Relativity at
the Galactic Center
(K band)
100 as astrometric
accuracy  5” from GC
Need to quantify. Already
very close to meeting this
requirement with KII AO.
√
Galaxy Assembly
(JHK bands)
Extrasolar planets
around old field brown
dwarfs (H band)
Contrast ratio H > 10 at
0.2” from H=14 star
(2 MJ at 4 AU, d* = 20 pc)
Meets requirements
(determined by static
errors)
√
Multiplicity of minor
planets (Z or J bands)
Contrast ratio J > 5.5 at
0.5” from J < 16 asteroid
Meets requirements: WFE
= 170 nm is sufficient
√
39
How does NGAO fit into
the competitive landscape
• Other ground-based observatories
• JWST & ALMA
• TMT
40
40
NGAO in the world of 8-10 m telescopes:
Uniqueness is high spatial resolution, shorter l’s, AO-fed NIR IFS
Table 1. Next-Generation AO Systems Under Development for 8 - 10 meter Telescopes
Type
Telescope
High-contrast
Subaru
High-contrast
VLT
High-contrast Gemini-S
GS
Next-Generation AO Systems
for 8 to 10 m telescopes
N/LGS Coronagraphic Imager Hi(CIAO)
Capabilities
Dates
Good Strehl, 188-act curvature,
4W laser
2008
NGS
Sphere (VLT-Planet Finder)
High Strehl
2010
NGS
Gemini Planet Imager (GPI)
Very high Strehl
2010
Wide-field
Gemini-S
5 LGS
MCAO
2Õ FOV
2009
Wide-field
Gemini
4 LGS
GLAO
Feasibility Study Completed
?
Wide-field
VLT
4 LGS
HAWK-I (near IR imager) +
GRAAL GLAO
7.5' FOV, AO seeing reducer,
2 x EE in 0.1''
2012
Wide-field
VLT
4 LGS
MUSE (24 vis. IFUs) +
GALACSI GLAO
1' FOV; 2 x EE in 0.2" at 750nm
2012
Narrow-field
VLT
4 LGS
MUSE (24 vis. IFUs) +
GALACSI GLAO
7.5Ó FOV, 10% Strehl @ 750 nm
in best seeing, low sky coverage
2012
•
Most 8-10 m telescopes plan either high contrast or wide field AO
•
Only VLT has narrow-field mode, but has low sky coverage and needs best seeing
41
41
Competitive Landscape: ALMA
• Millimeter and sub-millimeter
wavelengths (0.35 - 9 mm)
• Typical spatial resolutions ~ 0.1”
• Resolutions for widest arrays as
low as 0.004” at the highest
frequencies
• ALMA science: regions colder and
more dense than those seen in the
visible and near-IR by NGAO
• Keck NGAO and ALMA
observations complementary for:
– Spatially resolved galaxy
kinematics, z < 3
– Debris disks and young stellar
objects
42
42
NGAO comparison to JWST & TMT
Diffraction-limit (mas) at 2  m
Diffraction-limit (mas) at 1 m
Sensitivity
Imager
Detector
Wavelength range ( m)
Sampling (mas/pixel)
FOV (arcsec)
Spectrometer
Detector
Wavelength range ( m)
WMKO NGAO
41
20
1x
NGAO Imager
H4RG
0.8-2.4
8.5
35
NGAO IFS
H4RG
0.8-2.4
Spectral Resolution
Spatial Resolution (mas)
R~4000
10, ~25 & ~60
FOV (arcsec)
Projected 1st science paper
0.8, 2 & 4
~2015
JWST
63
limited by sampling
~200x at 2 m
NIRCam
4x H2RG
0.6-2.35
31.7
130
NIRSpec
2x H2RG
0.6-2.35
R~100 & ~1000
multi-object modes
R~3000 IFU or longslit modes
~100
200 FOR
4 slit; 3x3 IFU
~2014
TMT NFIRAOS
14
7
~80x
IRMS
IRIS Imager
H4RG
H2RG
0.8-2.5
0.8-2.5
4
60
15
120
IRMS
IRIS IFS
H2RG
H4RG
0.8-2.5
0.8-2.5
R=3270
Two image
(0.24" slit)
slicers;
R=4660
R~4000
(0.16" slit)
160
4 to 50
up to 3
120 FOR
~2020
43
NGAO comparison to JWST
Key Science Case
Galaxy Assembly
(JHK)
Nearby AGNs (Z)
General Relativity at
Galactic Center (K)
Extrasolar Planets
around old Field
Brown Dwarfs (H)
Multiplicity of Minor
Planets (Z or J)
JWST & NGAO
JWST much more sensitive at K.
NGAO sensitivity higher between OH lines at H.
NGAO sensitivity higher for imaging & spectroscopy at J.
NGAO wins in spatial resolution at all l.
NGAO provides higher spectral resolution.
Only NGAO provides needed spatial resolution (especially at Ca triplet).
Only NGAO provides needed spatial resolution (especially important to
reduce confusion limit).
Long term monitoring may be inappropriate for JWST.
Only NGAO provides needed spatial resolution.
JWST coronagraph optimized for 3-5 m, >1"; NGAO competitive ² 2
m, <1".
Only NGAO provides needed spatial resolution.
44
NGAO comparison to TMT
•
NGAO & NFIRAOS wavefront errors are similar (162 vs 174 nm rms).
– Similar Strehls. TMT will have higher spatial resolution and sensitivity.
– NGAO advantages: earlier science, accumulate experience that TMT will benefit from.
NGAO will screen most important targets for TMT (time scarce), do synoptic obsns.
Key Science Case
Galaxy Assembly
(JHK)
Nearby AGNs (Z)
General Relativity at
Galactic Center (K)
Extrasolar Planets
around old Field
Brown Dwarfs (H)
Multiplicity of Minor
Planets (Z or J)
TMT & NGAO
TMT IRIS lenslets (0.004″/px, 0.009″/px) have outstanding spatial resolution. TMT
IRIS slicer (0.025"/px, 0.05"/px) gives same spatial resolution as NGAO IFU. TMT
has higher sensitivity. NGAO may do many Z < 3 targets before TMT.
NGAO will screen most important targets for TMT. With 3x higher spatial resolution
TMT will detect smaller nearby black holes, and more distant large black holes.
NGAO IFU: good performance at 850nm Ca triplet is specific requirement. Could
potentially go to shorter wavelengths (e.g. Ha).
TMT wins in spatial resolution, sensitivity less important (confusion limited).
Significant value in continuing NGAO astrometry into TMT era (MCAO field stability
concern; Keck access easier). NGAO synoptic advantage.
TMT spatial resolution an advantage.
Control of static wavefront errors & PSF characterization will be critical (NGAO will
have 5 year head start on experience which TMT can learn from).
NGAO synoptic advantage.
TMT spatial resolution an advantage but NGAO could move to shorter l.
A lot of this science could be done by NGAO before TMT.
NGAO synoptic advantage.
45
Science Team Tasks During PD Phase
•
Ensure that the NGAO science cases fulfill our goals of keeping Keck
uniquely powerful and competitive by producing outstanding science.
•
Expand upon goals of “Science Drivers”, and finish documenting the AO
performance requirements necessary to achieve these goals.
– Iterative with AO Systems Engineering group
•
Detailed science simulations of “Key Science Drivers” to assess the
required level of PSF accuracy, stability, uniformity, and knowledge as a
function of position and time. Collaboration with IRIS team. Implications for:
– achievable astrometric and photometric accuracy
– achievable contrast ratio
– morphological and spectroscopic studies
•
Incorporate instrument design characteristics as these develop
•
Develop detailed observing scenarios for each “Key Science Driver” to
define pre- and post-observing tools and observing sequences.
46
Community Input to Science Team
Efforts
• Continued discussions with Keck community to ensure that science
case requirements remain consistent and up-to-date with advancing
discoveries, changing methodology, modifications to the current AO
system design, and maturing instrument concepts.
• Input from observers to improve planning tools, observing practices,
support, and efficiency.
• Feedback regarding NGAO science opportunities that complement
other ground-based AO and space-based facilities, and that take
advantage of the uniqueness space provided by NGAO at Keck.
47
A Key Issue:
What are the requirements for
PSF stability and knowledge?
• In System Design phase, we stated requirements in terms of
photometric and astrometric accuracy
– Develop error budgets
• These in turn need to flow down to specific levels of PSF stability,
uniformity, and knowledge
– “Stability” refers to temporal uniformity
– “Uniformity” refers to spatial uniformity (specify over what field)
– “Knowledge” -- no matter what the actual stability and uniformity, how
well do you know the PSF that pertained during a specific science
exposure?
• Develop a set of quantitative measures of “PSF Knowledge”
– Different science cases are sensitive to different aspects of the PSF
– Examples: total energy in core, details of halo, FWHM of core, etc
48
Science Operations Design
• Complexity of NGAO requires that we have a good science
operations plan and supporting software.
• We are developing an Observing Operations Concept Document
(OOCD) to detail observing process for each science case
• Science operations design optimizes observing efficiency:
(e.g., >80% open shutter time for high-z galaxies)
– Pre-observing tools: selection of guide stars, performance and SNR
prediction, planning and saving the observation sequences.
– Operations tools integrating NGAO, telescope and instruments,
allowing for parallel command and multi-system coordination.
– Dithering/offsetting/centering using internal steering optics, that do not
require opening/closing AO loops and offsetting the telescope.
• Quality of the final data product:
–
–
–
–
Use of WFC and ancillary data for monitoring atmospheric conditions
and image quality (SR, EE, photometry, etc).
Data archiving for calibration and science products.
PSF calibration, including PSF reconstruction from telemetry.
Post-processing software for IFU data.
49
Science Operations Design
Pre-observing tools
GUIs and high-level operations tools
Multi-system Command
Sequencer
Subsystem Command Sequencer
50
NGAO Design and Performance
NGAO System Architecture
Key Features:
1. Fixed narrow field laser tomography
2. AO corrected NIR TT sensors
3. Cooled AO enclosure smaller
4. Cascaded relay
5. Combined imager/IFU instrument
52
Strehl Ratio versus Laser Power
Science Strehl vs. Laser Power in Science Asterism
Science band Strehl Ratio
for 10” radius 3+1 “Tetrad” Asterism
50W in
science
asterism
Laser Power in the Science Asterism [Watts]
at spigot for assumed SOR-like return
53
Galaxy Assembly Performance vs. Sky Coverage
EE70mas
andTip-Tilt
Tip-TiltError
Error
SkyCoverage
Coverage
EE and
vs.vs.
%%Sky
GalaxyAssembly
Assembly case,
median
seeing
forforGalaxy
case,
median
seeing
16.00
100%
80%
70%
10.00
60%
1d Tilt Error (mas)
8.00
50%
40%
6.00
% EE (41 mas)
30%
4.00
20%
2.00
Tip-Tilt Error
EE 70 mas
EE 41 mas
1-D Tip-Tilt Error, RMS (mas)
Error, RMS
1-D Tip-TiltError
mas]
[rms(mas)
1-D Tip-Tilt
% EE (70 mas)
12.00
H-band Ensquared Energy
Ensquared Energy
H-band
90%
14.00
10%
0.00
0%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Sky Fraction
Fraction
Sky
K-band
b = 30
Complete sky coverage for IFS galaxy assembly science
EE70mas and Tip-Tilt Error vs. % Sky Coverage
54
0%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
Sky Fraction
Minor Planets Performance vs. Sky Coverage
Strehl Ratio
Ratioand
andTip-Tilt
Tip-TiltError
Errorvs.
vs.%%Sky
SkyCoverage
Coverage
Strehl
Minor
Planetscase,
case, median
median seeing
forfor
Minor
Planets
seeing
33 mas
17 mas
100%
90%
14.00
80%
12.00
70%
10.00
60%
8.00
50%
40%
6.00
30%
4.00
Ratio
Z-band Strehl
Ratio
Strehl
Z-band
p-Tilt Error
(mas)
Tip-Tilt Error,
mas]
[rms
ErrorRMS
Tip-Tilt
1-D1-D
16.00
Tip-Tilt Error
Strehl Ratio
20%
2.00
Strehl
0.00
10%
0%
0%
10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
SkyFraction
Fraction
Sky
z-band
b = 30
z-band Strehl > 20% for 50% sky coverage at b=30
55
Performance versus Seeing
Science Strehl vs. Seeing Parameter
Strehl Ratio in the respective Science Band
for 10” radius 3+1 “Tetrad” Asterism
Median
37.5%
87.5%
r0 (meters)
High Strehl for a wide range of seeing
56
Off-axis Performance
Field Performance for Galactic Center
Performance
Imaging radius
requirement
Max. IFU
radius
Max. imager
radius
Off-axis Distance [arcsec]
Median seeing
57
K2 Center Launch + New Laser
MRI proposals - Predicted Performance for T Dwarf Binary Case
Relative Positional Error
Relative Positional Error (mas)
2.50
Current K2 LGS AO
+ Center Projection
2.00
+ New Laser
1.50
Factor of 2x improvement  6x
in dynamical mass determination
1.00
0.50
0.00
0.05
0.1
0.15
0.2
0.25
0.3
0.35
Strehl Ratio (K-band)
Relative Magnitude Error
Relative Error (delta mag)
0.07
0.06
Current K2 LGS AO
0.05
+ Center Projection
+ New Laser
0.04
R = 16.2 NGS 31” off-axis
50 zenith angle
0.03
0.02
1% photometry
0.01
0.00
0.05
0.1
0.15
0.2
0.25
Strehl Ratio (K-band)
0.3
0.35
58
Science Instruments
Background
• NGAO science requirements established a need for
certain capabilities in the SD phase
– Imaging
• ~700 nm to 2.4 µm
• high contrast coronagraph
– Integral field spectroscopy in near-IR and visible
•
•
•
•
spatially resolved spectroscopy for kinematics and radial velocities
high sensitivity
high angular resolution spatial sampling
R ~ 3000 to 5000 (as required for OH suppression and key
diagnostic lines)
• Improved efficiency
– larger FOV
– multi-object capability
60
Constraints & Opportunities
• Constraints
– Cost
• Need to provide capability within a limited amount of funding
• Must understand which requirements drive cost
– Complexity
• Must resist the temptation to add features
• Maximize heritage from previous instruments
• Opportunities
– NGAO offers extended wavelength coverage
• Significant performance below 1 µm, Strehl ~20% at 800 nm
• Substrate removed HgCdTe detectors work well below 1 µm
– Exploit redundancies in compatible platforms – e.g. Near-IR
imager and Near-IR IFS
61
Wavelength Coverage
• CCD vs. IR FPA
– Substrate removed HgCdTe detectors work well below 1 µm
– ~20% lower QE than a thick substrate CCD
– Non-destructive readout takes care of higher read noise of IR array
LBNL QE
100.00%
H2RG QE
100.00%
90.00%
90.00%
80.00%
80.00%
Y
J
K
H
70.00%
NGAO
z spec
Transmission, %
Transmission, %
70.00%
60.00%
NGAO z'
50.00%
60.00%
Teledyne min. spec. for
substrate removed
H2RG
50.00%
40.00%
NGAO i'
30.00%
40.00%
NGAO rl
20.00%
NGAO visible
10.00%
30.00%
20.00%
0.00%
NGAO near-IR
0.5
0.6
0.7
0.8
0.9
1
1.1
1.2
Wavelength, m
10.00%
0.00%
0.3 0.4 0.5 0.6 0.7 0.8 0.9
1
1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9
2
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9
3
Wavelength, m
62
NGAO Imaging Capability
•
Broadband
– z, Y, J, H, K (0.818 to 2.4 µm)
– photometric filters for each band plus narrowband filters similar to NIRC2
•
Plate scale
– 1 or more plate scales selected to optimally sample the diffraction limit, e.g.
(l/2D), 8.4 mas at 0.818 µm
– Finer sampling may be important for photometry, astrometry
– Science requirement for ≥ 20" diameter FOV
@z band cut-off (0.818 m)
Sampling
Pixel scale
Detector size
2048 x 2048 (H2RG)
4096 x 4096 (H4RG)
l/2D(mas)
l/3D(mas)
8.4
5.6
FOV (")
17.3
11.5
34.6
23.0
– Multiple plate scales increase cost and may limit performance
•
•
•
Simple coronagraph
Throughput ≥ 60% over full wavelength range
Sky background limited performance
63
NGAO IFS Capability
• Narrowband
– z, Y, J, H, K (0.818 to 2.4 µm)
– ~5% band pass per filter, number as required to cover each wave band
• Spectroscopy
– R ~4,000
– High efficiency e.g. multiple gratings working in a single order
• Spatial sampling (3 scales maximum)
• 10 mas e.g. (l/2D) at 1 µm
• 50 to 75 mas, selected to match 50% ensquared energy of NGAO
• Intermediate scale (20 or 35 mas) to balance FOV/sensitivity trade off
• FOV on axis
– 4" x 4" at 50 mas sampling
– possible rectangular FOV (1" x 3") at a smaller spatial sampling
• Throughput ≥ 40% over full wavelength range
• Detector limited performance
64
Narrowband Science
• Extra-galactic
– IFS will be used for targets with known redshifts
• Therefore 5% bandpass sufficient?
• 5% spans Hα and NII lines for example
– 4 narrowband (5%) filters will cover the K-band
– Excitation temperatures
•
•
•
•
Need at least 4 lines
Can expect to get 2 or more in each filter
Can optimize center wavelength to maximize this
Practical to use 2 or more exposures to get enough lines
– Imaging spectrograph allows you to detect, and discount image motion for better
photometric matching of spectra
– Need to have enough FOV to ensure you cover the whole object in each exposure
• Exoplanet detection
– Broadband filters available with narrow FOV ~1" x 1"
65
Narrowband Science
• Nearby AGN (Black Holes)
– Galaxy kinematics
• CO bandhead 4 to 5% wide (OSIRIS Kn5 filter)
• Brackett gamma, H_2 emission lines (OSIRIS Kn3 filter)
– Remain in that passband to z = 0.03
• Same arguments on practicality of non-simultaneous spectra apply
– Central Black Hole
• Narrowband adequate for measuring black hole mass (only 1 line)
• ~1“ diameter FOV
• Galactic Center (e.g. GR effects)
– Narrowband acceptable for RV measurements
– Being used now
– Want better SNR
• Throughput
• Higher angular resolution to reduce stellar confusion, but keep present FOVs
– Could use more FOV
66
Where can the NSAT best contribute?
NGAO Team Suggestions
67
Potential NSAT Contributions:
based on the Charter
• The purpose of the SAT is to help ensure that the NGAO facility will provide
the maximum possible science return for the investment, and that NGAO will
meet the scientific needs of the Keck community.
• To that end the SAT will provide science advice to the NGAO project, with an
emphasis on the further development of the science cases and science
requirements. For example:
– Advice on overall science priorities
– Ensuring that NGAO will play a long term vital role in the era of TMT, JWST, etc.
– Advice when there are design trades to be made (science benefit vs. added cost
or complexity; priorities between the various science cases)
– Advice on the science instrument concept and requirements
• Seeking community input & informing the community about NGAO
developments
68
68
Potential NSAT Contributions
•
We seek your help in the following near-term areas:
– Strengthening the science cases & the definition of the science
requirements for NGAO & the NGAO science instruments 
Science Case Requirements Document (KAON 455)
• Ex., science case for optical wavelengths
– Provide guidance on the Observing Operations Concepts to ensure
they meet the scientific needs of the users  Observing
Operations Concept Document (KAON 636)
– Understanding what factors limit science performance (astrometry,
photometry, contrast, sensitivity, observing efficiency, PSF
knowledge, etc.)
– Participating in the development of the science instrument
requirements and concept
– Science input to proposals (Federal & private; MRI-R2 by Aug. 10)
69
Some areas in which we could use help
from students or postdocs
In many cases the underlying work could be done by grad students or postdocs
(would like your help in engaging students & postdocs):
• Further develop the science cases for optical wavelengths
– Science benefit, if any, of working at shorter l, but lower Strehl (e.g. Ha)
•
How stable and well-known does the PSF have to be, for the various
science cases
– AGNs and quasars, planets around low-mass stars, astrometry applications
•
Science simulations in support of the IFU design
– Trades between high spatial resolution and high sensitivity, for specific scenarios
•
Astrometry error budget for the Galactic Center
– Which aspects are understood today
– Of the ones not yet understood, which are most important to tackle 1st
•
Resolved stellar populations science case needs to be quantified
– Start by choosing 1 or 2 specific science scenarios that make sense given
NGAO’s high Strehl but small field of view
•
Several specific issues involving strategies for high contrast imaging
70
How would you like to help?
• Are there areas that you think we missed?
• What additional information do you need?
• What can we sign you up for?
71