MCAOMCAO
System OverviewSystem Overview
Brent Ellerbroek
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
Presentation OutlinePresentation Outline
• Primary subsystems and their characteristics– Laser System (LS)– Beam Transfer Optics (BTO) and Laser Launch
Telescope (LLT)– Adaptive Optics Module (AOM)– MCAO Control System (MCAO CS)– Safe Aircraft Localization and Satellite Acquisition
System (SALSA)
• System performance summary– Strehl– Strehl variability– Transmittance and Emissivity– Availability and Reliabilty
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
System Block DiagramSystem Block Diagram
LS
SALSA
LLT
BTO
AOM
TCS/SCS/OCS/DHS
OIWFS
ScienceInst.
Laser/LGSNGS
Science field
(BoresightCalibration)
Real-TimeControl
FunctionalControl
MCAO CS
Emergencyhalt
Safety status
Telescope pointing
Observing sequences
Data logging
M2/M1offloads
CommandsStatus
Fast tip/tilt
Diagnostics
Beamalignment
WFS data
DM/TTMcommands
Close/open loops
Calibration functions
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
Laser and LGS ParametersLaser and LGS Parameters
Number of LGS 5
LGS locations in Field (0,0) and (+/-30,+/-30) arc sec
LGS signal at WFS 125 PDE’s/cm2/sec (80 with regrets)
LLT/BTO transmittance 0.72/0.54 (laser on/off telescope)
Laser power per LGS 6-15 Watts
Transmitted beam quality
1.5 time diffraction limited
RMS 1-axis beam jitter 0.05 arc sec
1/e2 beam diameter 0.3 m
LLT diameter, location 0.45 m, behind secondary
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOBTO andBTO andLLT LLT SchematicSchematic
BS
Pointing Array (PA)
Top-End Ring Mirror
KM
LLT
CenterSection
TopEnd
Relay
BDS
Centering mirror (CM)
Fast Steering Array
Pointing mirror (PM)
Centering Array (CA)
X-Shaping Mirrors
Periscope
PM, CM
PAC
PA, CA
PAC
PA, CA
PAC
PreAlignment
Beam position & tilt
LGS WFS
Offload to KM, PM, CM
PA, CA
MCAOCS
MCAOCS
Closed-loopAlignmentControl
CCShutter
BoresightCalibration
PS
LLT cover
Near- and far-field beam profiles
/4 Plate
Beam Dump Mirror
/4 Plate
Safety Shutter(SALSA)
MiscellaneousFeatures
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
Science Path
OAP1 OAP2
DM9DM0
TTMDM4.5
SCIBS ADC
NGS WFS Path
OAP3WFS
WFSBS
ADC
LGS WFS Path
Zoom FocusLens
LGS WFS
Other Stuff
SourceSimulators
DiagnosticWFS andImagingCamera
• f/33.4 output
• Focal- and pupil plane locations preserved
• Standard optical bench design with space frame support
• In-plane packaging with adequate room for electronics
Adaptive Optics ModuleAdaptive Optics Module
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOBaseline AO Component Baseline AO Component ParametersParameters
Number of DM’s 3
DM conjugate ranges
0.0, 4.5, 9.0 km
Actuator pitch D/16, D/16, D/8
Number of WFS 5 (LGS) 3 (NGS)
WFS order 16 by 16 Tip/tilt
Pixels/subaperture 4 by 4 (2 by 2 used)
2 by 2
WFS pixel subtense 1.0 arc sec 0.5 arc sec
WFS read noise 6 electrons None
AOM throughput 0.65 0.6
Detector QE 0.95 0.60
WFS sampling rate 800 Hz
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
Higher-order wavefront control
Tip/tilt (tt) and tilt aniso-
Planatism (ta) control
Real Time Control Block Real Time Control Block DiagramDiagram
DM’s
Null uncon-trolled modes
TTM
BTO tip/tilt
LGS WFS’s
NGS WFS’s
+
Integrator
IntegratorOIWFSFocus
OIWFSTip/tilt
Focusadjustment
Boresightadjustment
M2Offload
M1/M2Offload
Tip/tilt
Higher order
tt
ta
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
MCAO Control SystemMCAO Control System
Instrument Sequencer
1
Real TimeController
3
AOM Component Controller
2
BTO/LLTComponent Controller
4
SALSAController
5
LaserController
6
Laser hardware
SALSA hardware
BTO/LLT devices
AOM devices
AOM WFS/DM/TTM
OCS command OCS command status
BTOFast TT
NGSprobe offset
DWFSDetector
Controller7
Controller commands/status
commands/status commands/statuscommands/status commands/statusWFS data/DM commands
PupilAlignment
Observing data
TCS pointing
Oiwfs data
M2 data
M1 data
seeing
(CR angleOffset)
CR angle
TCS pointing
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
SALSA ElementsSALSA Elements
• Boresighted IR aircraft camera• All-sky aircraft cameras• Laser traffic control arbitration with local
observatories• Available radar feeds from air traffic control
agencies (TBD)• US Laser Clearinghouse interface (TBD)
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
Strehl Ratio SummaryStrehl Ratio Summary
Zenith 30 Degrees 45 Degrees
0.85 microns
0.031 0.010 0.002
1.25 microns
0.201 0.121 0.052
1.65 microns
0.398 0.298 0.184
2.20 microns
0.596 0.506 0.386
• Median Cerro Pachon seeing• Mean Strehls over 1 arc minute square field• Delivered Strehls at the detector• Bright NGS• Detailed error budgets in system modeling presentation
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOPerformance with an Interim Performance with an Interim Laser ComplementLaser Complement
• Initial MCAO laser configuration may be reduced for reasons of schedule or cost
• Growth path to the full laser system should be maintained
• One possible interim laser configuration:– 60% nominal laser power, split into– 1 full power and 4 half power laser guide stars
0.9300.9450.976H
Strehl Ratio Reduction
Corner FoV
Edge FoVCenter FoV
Spectral band
0.8880.9100.959J
0.9580.9680.985K
Expends Margin• Sodium column density• Laser power and beam quality
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAORMS Relative Strehl RMS Relative Strehl NonuniformityNonuniformity
LGS Signal Wavelength
Zenith 30 Degrees
45 Degrees
125 PDE’s/cm2/sec
1.25 m 0.068 0.098 0.181
1.65 m 0.040 0.058 0.106
2.20 m 0.023 0.033 0.060
80 PDE’s/cm2/sec
1.25 m 0.071 0.101 0.186
1.65 m 0.042 0.060 0.110
2.20 m 0.025 0.035 0.064• 1 square arc min field, median Cerro Pachon seeing, bright NGS• CoDR results
• Linear modeling• Neglect effects of diffraction, 3-d LGS, DM-to-WFS misregisration, and other implementation error sources• Initial simulation results including these effects see no significant change
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAOScience Path Transmittance Science Path Transmittance and Emissivityand Emissivity
Wavelength 1.00 m 1.65 m 2.20 m 2.20 m(emissivity
)
Per reflection 0.979 0.986 0.987 0.013
Per air-glass I/F 0.991 0.987 0.989 0.011
Beamsplitter (net) 0.930 0.960 0.965 0.022
Overall, 9 reflections
0.826 0.881 0.889 0.117
Overall, no ADC 0.768 0.845 0.858 0.139
4 ADC air/glass I/F 0.965 0.949 0.957 0.044
Overall, with ADC 0.742 0.802 0.821 0.183
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
System AvailabilitySystem Availability
Total Unavailable Time
Laser Pulse Format
Overhead Scenario Satellite Loss
Pulsed CW (MCAO)
Full setup + astrometry 12.9% 30% 38%
Partial setup + astrometry 11.8% 29% 37%
Partial setup, no astrometry
9.1% 27% 35%
Dwell on fixed object 43.0% 54% 59%• Astrometry adds extra setup time for plate scale determination • CW laser penalty is due to LGS interference with thin cirrus
• Conventional LGS AO still feasible• Includes system downtime of 10%
• Met with laser MTBF of 48 hours
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
SummarySummary
• Overall system architecture equivalent to conventional LGS AO
• Significant subsystem design progress since CoDR• Delivered H-band Strehl of 0.398
– Median CP seeing, zenith, bright NGS, average for a square 1 arc min field
• Useful performance for an interim laser system with 60% power– Strehl ratio reduction factors of 0.888 to 0.985
• RMS relative Strehl nonuniformity of 0.04 in H• Science path throughput of 0.80-0.85 in H band,
emissivity of 0.14-0.18 in K• System availability of 62-73% with queue
scheduling
May 24-25, 2001 MCAO Preliminary Design Review
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MCAOMCAO
PDR AgendaPDR Agenda
Thursday, 5/240800 Welcome 0805 Project overview 0830 Science case0930 Break0945 System overview1015 System modeling1100 AO Module optics1145 Lunch
1245 AO Module mechanics1340 AO Module electronics1400 Break1415 Beam Transfer Optics1510 Laser Launch
Telescope1545 Closed committee
session1800 Adjourn