WMKO Next Generation AO system: project status report

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Simulations for Keck NGAO science cases
performance budgets
Chris Neyman Ralf Flicker Peter Wizinowich WM
Keck Observatory September 14, 2006
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This presentations provides a forum to discuss
our ideas for coordination of simulations, trade
studies and science test cases
Status of simulations
Model assumptions
Testing validation
Science case support
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NGAO proposal wavefront allocations need
anchoring and further analysis
NGAO Error Budget Example KBO imaging scenario
Key green allocation All others supported by
detailed calculations
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NGAO proposal wavefront allocations need
anchoring and further analysis
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LAOS simulation status compatible with trade
study goals
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LAOS simulation status compatible with trade
study goals (cont.)
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Checking assumption and model inputs necessary
starting point for more detailed simulations
Verify that starting assumptions are
representative of Keck and Mauna Kea
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TMT site monitor data provides, total seeing from
DIMM and Turbulence profiles from MASS.

• MASS
• provides Cn2
• Calc. q0 r0 d0
• wind infer fG

• DIMM total
• DIMM-MASS ground layer

• Correlation between MASS and DIMM

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Boundary layer at TMT site (13N) different than
at Keck dome and summit ridge (Gemini, CFHT,
Subaru)
13 N is 400m and 100m down slope from Keck
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Boundary layer difference between Subaru, CFHT,
UH (data from Mauna Kea weather center)
Winds from the ESE Wind speed 10 mph
Others July 12, 30 Aug, 4 to 7.
http//mkwc.ifa.hawaii.edu/archive/mko
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Keck laser return and model (Milonni,99)
consistent with Na layer abundance from Maui
LIDAR

• Keck Laser
• 23 observations
• (May-June 06)
• Milonni JOSA A 1999
• Maui MALT
• 35 nights
• 979 data points
• (2002-2005)

Keck Laser median 2.47x10-9 atoms cm-2 Maui MALT
median 3.60x10-9 atoms cm-2
http//conrad.csl.uiuc.edu/Research/Maui/NaLidar/i
ndex.html
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P. Milonni, R. Fugate, J. Telle, Analysis of
measured Photon Return form Sodium Beacons, JOSA
A, Vol. 15, No. 1,1998

• Anchored to LLNL dye laser data
• The flux at the telescope pupil in photons cm-2
  sec-1 is given by,

Keck Laser median 2.47x10-9 atoms cm-2 Maui MALT
median 3.60x10-9 atoms cm-2
where Plaser is the average output laser power,
tp is the laser pulse length, Rp is the pulse
repetition rate, Isat 5W/cm2 is the saturation
intensity for pulsed lasers, A 1/(16ns) is the
radiative decay rate for sodium atoms, a is the
spot FWHM at the sodium layer, z is the range to
the sodium layer from the telescope, Cs is the
sodium column density in atoms cm-2, Tatmos is
the atmospheric transmission and Tbeam is the
beam train transmission.
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Cloud cover and Cirrus from satellite study,
needed to predicted observing uptime and Rayleigh
background in WFS
Findings for Mauna Kea 69 photometric (included
fract. nights) 9 Spectroscopic 22 Cloudy
(unusable) Only calibrated to extinction
Erasmus and van Staden, Study for AURA A
Comparison of Satellite-Observed Cloud Cover and
Water Vapor at Mauna Kea and Selected Sites in
Northern Chile and SW United States and Northern
Mexico
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Model validation and comparison need for
confidence when extrapolating to new systems
Focus on plan for Tomography errors between
LAOS and Gavels Spherical Tomography (IDL)
Other important anchors Keck II LGS PSF Lab for
AO MCAO test bed
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Our plan for understanding discrepancies in
Tomography error from simulations
Summarize runs that have been done so far - list
the parametric assumptions and the results. (NGAO
proposal cases) Re-do the case where they
significantly disagree, this time carefully
making sure our parameter inputs are in fact the
same Run tests that quantify code behavior with
respect to individual assumptions/inputs, for
example o Do a noise-free "phantom" case, that
is, using a unit aberration at some altitude and
verifying that the codes produce identical
results, o Model the response to just
measurement noise, no aberrations, and make sure
codes produce the right variance in the solution
o Test solutions with one guidestar, first at
infinity, then at LGS altitude o Test solutions
with three guidestars on a triangle. Check
results vs. angular separation.
http//www.oir.caltech.edu/twiki_oir/bin/view.cgi/
Keck/NGAO/ModelValidation
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Atmospheric phantom idealized test for tomography
(courtesy Don Gavel)
http//www.oir.caltech.edu/twiki_oir/bin/view.cgi/
Keck/NGAO/ModelValidation
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NGAO proposal test cases
http//www.oir.caltech.edu/twiki_oir/bin/view.cgi/
Keck/NGAO/ModelValidation
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System Design phase explores science capability
balanced against technical feasibility
Consider some key science use cases Consider some
associated drivers
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High Z galaxy test case requires trades for AO
multiplex and sensitivity
Science multiplex vs. AO correction
IR background traded against num. optics
LAOS can simulate MOAO MCAO and GLAO
architectures
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Companion sensitivity test case requires control
of systematic effects

• High Strehl over small FOV
• Control systematic errors from 3D LGS, telescope,
  instrument

• Details of diffraction suppression
• Coronograph design
• Lyot or something else?

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Stellar population case requires photometric
calibration from AO images across FOV

• Calibration of PSF contamination inside clusters
  and nearby galaxies

• Simulate PSF for
• 1d-apeture corrections
• 2d PSF fitting

• Understand variability of conditions and AO perf.
• AO telemetry and Cn2 information

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Galactic center performance dominated by residual
tip tilt and standard astrometric errors
Camera distortion Diff. Chrom. Refraction CCD
centroid Reference frame Tip tilt
anisoplanatism GC field is small HO
anisoplantism LTAO vs KECK II LGS
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Residual tip tilt results in field distortion
5 Laser guide stars 1 tip/tilt NGS
No AO
5 Laser guide stars 3 tip/tilt NGS

• Numerical simulations
• 5 Wavefront sensors
• 2 mirrors
• 8 turbulence layers

• MK turbulence profile
• Field of view 1.2
• H band

Annimation courtesty GEMINI AO group
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Planning needed for next stages of system design
Draft performance budget
Need direction priorities
Simulate complicated and large drivers
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Simulation plan from estimated need by dates of
science cases and trades studies
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In conclusion, we are developing simulation tools
to begin next iteration of system design
Thanks for your attention
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Keck specific simulation inputs

• Simulation infrastructure exists to handle
  telescope optical aberration and vibration
  effects
• Input as temporal and spatially varying phase
  screen for now. Integrated Modeling in the future
  (??)
• Need to verify
• the inputs to the simulation
• Some test inputs to simulation shown below

Segment phase errors
Vibration spectrum