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MCAO System Overview Brent Ellerbroek Presentation Outline MCAO • 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 2 MCAO System Block Diagram (Boresight Calibration) LLT Emergency halt BTO Fast tip/tilt Beam alignment Diagnostics LS SALSA MCAO CS Status Commands Safety status WFS data Close/open loops Functional Control Telescope pointing NGS Laser/LGS Science field May 24-25, 2001 Real-Time Control DM/TTM commands Observing sequences AOM OI WFS Science Inst. Calibration functions Data logging M2/M1 offloads TCS/SCS/OCS/DHS MCAO Preliminary Design Review 3 Laser and LGS Parameters MCAO Number of LGS 5 LGS locations in Field LGS signal at WFS (0,0) and (+/-30,+/-30) arc sec 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 May 24-25, 2001 0.45 m, behind secondary MCAO Preliminary Design Review 4 BTO and LLT Schematic MCAO Near- and far-field beam profiles Beam position & tilt PA, CA Miscellaneous Closed-loop Boresight Periscope Pre Alignment Calibration Features X-Shaping Control Mirrors BS PA, CA CC Top-End Ring Mirror Top End Center Section PAC PAC Relay Pointing Array (PA) PA, CA MCAO CS BDS Centering mirror (CM) Beam Dump Mirror Shutter LGS WFS KM Pointing mirror (PM) Fast Steering Array Offload to KM, PM, CM l/4 Plate LLT cover MCAO CS PAC Centering Array (CA) l/4 Plate Safety Shutter(SALSA) May 24-25, 2001 PS MCAO Preliminary Design Review LLT PM, CM 5 MCAO Adaptive Optics Module Science Path NGS WFS Path LGS Other WFS Stuff Path DM0 DM9 SCIBS ADC Source Simulators • f/33.4 output • Focal- and pupil plane WFSBS OAP1 locations preserved TTM • Standard optical bench DM4.5 design with space frame support • In-plane packaging with adequate room ADC for WFS electronics May 24-25, 2001 OAP2 Diagnostic WFS and Imaging Camera Zoom Focus OAP3 Lens LGS WFS MCAO Preliminary Design Review 6 Baseline AO Component Parameters MCAO 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 4 by 4 (2 by 2 used) 2 by 2 1.0 arc sec 0.5 arc sec 6 electrons None AOM throughput 0.65 0.6 Detector QE 0.95 0.60 Pixels/subaperture WFS pixel subtense WFS read noise WFS sampling rate May 24-25, 2001 800 Hz MCAO Preliminary Design Review 7 Real Time Control Block Diagram MCAO BTO tip/tilt OIWFS Focus Integrator M1/M2 Offload Focus adjustment Higherorder wave front control LGS WFS’s OIWFS Tip/tilt + Null uncontrolled modes Integrator Boresight adjustment NGS WFS’s Tip/tilt (tt) and tilt anisoPlanatism (ta) control Higher order ta tt TTM M2 Offload Tip/tilt May 24-25, 2001 DM’s MCAO Preliminary Design Review 8 MCAO MCAO Control System OCS command Controller commands/status CR angle Observing data M1 data Oiwfs data AOM Component Controller 2 (CR angle Offset) Pupil Alignment NGS probe offset Real Time Controller 3 BTO Fast TT commands/status WFS data/DM commands AOM devices AOM WFS/DM/TTM May 24-25, 2001 DWFS Detector Controller 7 Instrument Sequencer 1 TCS pointing seeing M2 data TCS pointing OCS command status BTO/LLT Component Controller 4 commands/status BTO/LLT devices MCAO Preliminary Design Review SALSA Controller Laser Controller 5 6 commands/status SALSA hardware commands/status Laser hardware 9 SALSA Elements MCAO • 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 10 MCAO Strehl Ratio Summary 0.85 microns 1.25 microns 1.65 microns 2.20 microns • • • • • Zenith 30 Degrees 45 Degrees 0.031 0.010 0.002 0.201 0.121 0.052 0.398 0.596 0.298 0.506 0.184 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 11 Performance with an Interim Laser Complement MCAO • 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 Strehl Ratio Reduction Spectral band Center FoV Edge FoV Corner FoV J 0.959 0.910 0.888 H 0.976 0.945 0.930 K 0.985 0.968 0.958 May 24-25, 2001 MCAO Preliminary Design Review Expends Margin • Sodium column density • Laser power and beam quality 12 MCAO RMS Relative Strehl Nonuniformity LGS Signal Wavelength 125 PDE’s/ cm2/sec 1.25 mm 0.068 0.098 0.181 1.65 mm 0.040 0.058 0.106 2.20 mm 0.023 0.033 0.060 1.25 mm 0.071 0.101 0.186 1.65 mm 0.042 0.060 0.110 2.20 mm 0.025 0.035 0.064 80 PDE’s/ cm2/sec Zenith 30 Degrees 45 Degrees • 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 13 Science Path Transmittance and Emissivity Wavelength 1.00 mm 1.65 mm MCAO 2.20 mm 2.20 mm (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 14 MCAO System 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% 9.1% 27% 35% 43.0% 54% 59% Partial setup, no astrometry Dwell on fixed object • 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 15 MCAO Summary • 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 16 MCAO PDR Agenda Thursday, 5/24 0800 Welcome 0805 Project overview 0830 Science case 0930 Break 0945 System overview 1015 System modeling 1100 AO Module optics 1145 Lunch May 24-25, 2001 1245 AO Module mechanics 1340 AO Module electronics 1400 Break 1415 Beam Transfer Optics 1510 Laser Launch Telescope 1545 Closed committee session 1800 Adjourn MCAO Preliminary Design Review 17