NGAO System Design Phase Update Peter Wizinowich, Rich Dekany, Don Gavel, Claire Max for NGAO Team SSC Meeting January 24, 2007.

NGAO System Design PhaseNGAO System Design PhaseUpdateUpdate

Peter Wizinowich, Rich Dekany, Don Gavel, Claire MaxPeter Wizinowich, Rich Dekany, Don Gavel, Claire Maxfor NGAO Teamfor NGAO Team

SSC MeetingSSC MeetingJanuary 24, 2007January 24, 2007

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Presentation Sequence

• SSC Co-Chair Questions

• Management UpdateA. Management StructureB. Systems Engineering Management PlanC. Documentation & Coordination D. Instruments Working GroupE. Project Report #1

• Technical Update– Science Requirements– Performance Budgets– Trade Studies

• Summary

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SSC Co-Chair QuestionsAll of the following questions are addressed in the Systems Engineering

Management Plan (summarized in the following Management update slides):

1. What is the product of this study phase?• Following Keck development process (see System Design phase

deliverables on slide 6). Includes conceptual design (with options), initial cost estimate & management plan for remaining project. Instrument concepts developed to proposal level (precursor to their System Design phase).

2. Are any intermediate reviews planned?• Frequent internal product reviews, including cost reviews in Aug & Dec.

SDR at end of this phase (3/31/08). Project reports provided prior to each SSC meeting.

3. Who is doing what, and what % of time is each person devoting to NGAO?• Details in project plan. High level summary of key personnel on slide 10.

4. What are the major goals/milestones of this phase?• See milestones on slide 9.

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SSC Co-Chair Questions

5. What are the big issues and how are they being addressed?• Big picture: Cost, schedule & performance + structuring the program to suit the

funding. Science & engineering team working closely with management to produce a compelling & realistic vision.

• Near term: Science community input & team ramp-up. Engaging scientists in science case requirements & performance budgets. Freeing personnel from other responsibilities.

6. What is the timescale for this phase and when can the SSC expect a full report?• See schedule on slide 15.

7. What is the relationship between the NGAO team and the AOWG– AOWG – Bouchez, Dekany, Koo, Larkin, Liu (co-chair), Macintosh, Marchis,

Matthews, Max (co-chair) + Ellis (rotating on)– The AOWG was a very active participant in the NGAO proposal.– Max, Liu & Marchis are leading the science case requirements– AOWG last met 8/06.

8. Comparison of NGAO versus planned AO performance of current generation. Why should we believe new models?– Addressed in the performance budgets section.

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A. Management Structure

• Proposal approved at Jun/06 SSC & Board meetings• WMKO, UCO & COO Directors subsequently established

an Executive Committee (EC) to manage System Design phase:

Wizinowich-WMKO (chair), Dekany-Caltech, Gavel-UCSC, Max-UCSC, CFAO (project scientist)

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B. Systems Engineering Management Plan (SEMP)

• SEMP submitted to Directors at end of Sept/06– Verbal approval received to proceed– Budget approval being finalized

• System design started Oct/06– Completion planned for mid-FY08

• Products of this study phase (Q1) - System design phase deliverables

– System Requirements Document - Science & Observatory requirements & flow down to system requirements

– System Design Manual – Performance budgets, functional requirements, system & subsystem architectures

– SEMP – For remaining NGAO phases– System Design Report – Summary for System Design Review

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B. SEMP: Approach

1. Initial focus on requirements & performance budgets to ensure that we understand largest levers on the design

2. Initial attempt at defining the AO system architecture & the functional requirements for the major systems

3. In parallel with 1 & 2 perform trade studies to better understand the appropriate design choices

4. A process of iteration and refinement will lead to the final version of the AO architecture & major systems requirements

• Includes continued development of performance budgets & functional requirements

5. Develop cost estimates & plans for remainder of NGAO project

Science Requirements

Technical Implications

Initial Concept

Performance Assessment

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B. SEMP: Budget

WBS Name

Cost ($k)

FY07 FY08 Total

1 Management 74 49 123

2 System Requirements 119 3 122

3 System Design 560 90 650

4 Systems Engineering Management Plan 5 79 84

Travel/Procurements 40 20 60

Contingency (part of overall Observatory contingency) 10 94 104

Total ($k) = 808 335 1143

Institute

Work (hours)

FY07 FY08 Total

COO 2836 702 3589

UCSC 2991 845 3926

WMKO 5355 1852 7360

Students 1850 0 1850

Total = 13032 3399 16725

$163k increase in cost of labor since proposal, due to distributed project nature

Total work same as in original proposal

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MILESTONE DATE DESCRIPTION

SD SEMP Approved 10/9/06 Approval of plan by Directors

SD phase contracts in place 10/27/06 Contracts issued to Caltech & UCSC for the system design phase

Science Requirements Summary v1.0 10/27/06 Initial Release of Science Requirements as input to trade

studies & performance budgeting

System Requirements Document v1.0 12/8/06 Initial release with emphasis on the science requirements

Performance Budgets Summary v1.0 2/27/07 1st round of all performance budgets complete & documented

System Requirements Doc v2.0 3/22/07 2nd release

Trade Studies Complete 5/25/07 All trade studies complete & documented (as a series of KAONs)

System Requirements Doc v3.0 7/12/07 3rd release of System Requirements

System Design Manual v1.0 8/31/07 1st release of System Design Manual

Technical Risk Analysis v1.0 11/13/07 1st round of project risk analysis complete & documented

Cost Review Complete 11/30/07 Project cost estimates complete, documented & internally reviewed

System Design Manual v2.0 1/8/07 2nd release

System Design Review Package Distributed 3/4/08 SDR documents sent to reviewers

System Design Review 3/31/08 SDR meeting

SDR Report & Project Planning Presentation at SSC meeting

4/14/08 Final SD phase report including results of SDR & project plans

B. SEMP:Milestones

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B. SEMP: TeamName Institute % NGAO-relevant Expertise

Bouchez COO 11 AO systems & science

Dekany COO 33 EC; AO systems & mgmt

Moore COO 31 Instruments

Velur COO 38 Lasers & wavefront sensors (mechanical)

Bauman UCSC 21 Optics

Gavel UCSC 33 EC; AO systems & mgmt

Max UCSC 22 EC Science Team chair

Postdoc UCSC 46 AO science

Adkins WMKO 15 Instruments & Project Mgmt

Chin WMKO 18 Electronics

Flicker WMKO 38 AO Modeling

Johansson WMKO 18 AO Control (software & electronics)

Le Mignant WMKO 15 AO science operations

Meguro WMKO 13 Mechanical

Neyman WMKO 67 AO systems

Wizinowich WMKO 36 EC chair; AO systems & mgmt

Represents 84% of the work force.

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C. Documentation & Coordination

• NGAO Twiki site at http://www.oir.caltech.edu/twiki_oir/bin/view.cgi/Keck/NGAO/WebHome

• Includes collections for– Team meetings

• Agendas & documents posted in advance; action items posted & followed up

– Executive committee• Planning & tracking documents

• EC weekly meeting minutes

– Work packages• Table of WBS elements, planning sheets & products

– Performance budgets• Meeting summaries & products

– Science team

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D. Instruments Working Group• Instruments Working Group (IWG) being formed for NGAO System Design

Phase– Focused on instrumentation related matters

• Instrument specialist perspective for NGAO• Resource for AO system design team on instrumentation issues

– Organization (6 to 8 members)• 3 to 4 funded from current NGAO plan

– Responsible for most of technical work related to NGAO instrumentation WBS– Sean Adkins (IWG chair, overall systems, detectors, electronics & interfaces)– Anna Moore (instrument generalist, optical & mechanical)– James Larkin/UCLA IR Lab staff members (instrument design, optical & mechanical, cryogenics

experience)– TBD software engineer

• 3 to 4 TBD volunteers from NGAO science team– Primary contacts with science team for instrument related science requirements

• Regular meetings will be held involving the entire group

• Additional assistance & advice will be sought from the diverse base of the collective instrumentation & technical resources at UC & CIT

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E. Project Report #1

• Directors’ requested written project reports prior to each SSC meeting

• 1st report submitted to Directors on Jan. 19http://www.oir.caltech.edu/twiki_oir/bin/view.cgi/Keck/NGAO/SystemDesignPhasePlanning

• Good progress made on initiating NGAO System Design phase & on building up an effective team

• Emphasis to date, as planned, on understanding the major design drivers through a process of iteratively developing the science case requirements & the performance budgets

• Work has begun on a number of trade studies in support of the performance budgets & the future design choices

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# MILESTONE DATE DESCRIPTION STATUS

1 SD SEMP Approved 10/9/06 Approval of this plan by the Directors. SEMP released to

Directors on 9/29/06.

Verbal approval received. Written approval requested

2 SD phase contracts in place 10/27/06 Contracts issued to Caltech & UCSC for the system design phase.

$50k initial contracts issued on 12/20

3 Science Case Requirements Summary v1.0 Release

10/27/06 Initial Release as input to trade studies & performance

budgeting

V1.0 to be completed in Jan/07

4 System Requirements Document v1.0 Release

12/8/06 Initial release of System Requirements with emphasis on

science requirements

V1.0 to be completed in Jan/07

5 Performance Budgets Summary v1.0 Release

2/27/07 1st round of all performance budgets complete & documented

Good progress

6 System Requirements Doc v2.0 Release

3/22/07 2nd release of System Requirements Document

Not started yet

7 Trade Studies Complete 5/25/07 All trade studies complete (Keck Adaptive Optics Notes)

Good progress

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Budget• $772k budgeted for FY07 in 5-year plan• $110k spent in 1st quarter

– Low due to slower than planned ramp up of personnel

– Average of 4.3 FTEs

Summary• Good technical progress as you will see in the following slides• Team and management processes now largely in place• Expect the teams rate of progress to be close to the rate in the plan

during the 2nd quarter

Science Case Requirements Science Case Requirements & System Requirements& System Requirements

Max, Ghez, Law, Liu, Lu, Macintosh, Marchis, Steidel

Neyman, Wizinowich

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Science Requirements Process

• Approach:– Start from significant science case development in proposal– Analyze limited set of these key science cases in order to

understand and document the requirements on NGAO + Instruments

– Begin with cases that stress AO design the most in multiple directions

– Progress to include more science cases– Iterate 4 times with AO & instrument requirements

• For each case, discuss– Science goals, proposed observations, AO performance

requirements, instrument requirements

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Science Requirements &

Performance Budget Process

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Science Case Requirements DocumentRelease 1 Contents

• JWST and ALMA capabilities• Future AO capabilities of other observatories• Key science cases and what they stress most:

– Multiplicity, size, shape of minor planets• High contrast, wavefront error, visible light performance

– Planetary & brown dwarf companions to low mass stars• High contrast

– General relativistic effects in the Galactic Center• Astrometry and radial velocity accuracy

– Assembly and star formation history of high z galaxies• Lower backgrounds, multiple deployable IFUs, sky coverage

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JWST capabilities

• Cryogenic 6.5-m space telescope, launch in 2013

• Higher faint-source sensitivity than Keck NGAO, due to low backgrounds

• Not diffraction limited below K band– Primary mirror spec– NIRCAM px scale 0.035”, NIRSpec px scale 0.1”

• Areas where Keck NGAO would complement JWST

– Spectroscopy @ spatial resolution better than 0.1”, = 0.6 - 2 μm

– Imaging @ spatial resolution better than 0.07”, = 0.6 - 2 μm

– Multi-IFU spectroscopy

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Key science requirements: 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, consider queue or flexible scheduling

Asteroid Sylvia and moons

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Key Science Requirements: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 arc sec

• Instruments:– Imaging 0.9 - 2.4 microns

– Single near IR IFU spectroscopy, still need to specify spectral resolution

• Observing modes: coronagraph needed

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Key Science Requirements: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 250 as) and radial velocity precision to 10 km/sec (now 20 km/sec)

• K band, wavefront error ≤ 170 nm• 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

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Key Science Requirements:Assembly and star formation history of high z galaxies

• Redshifts 1.5 ≤ z ≤ 2.5: most active star formation, form bulges & disks – Optical lines such as H are shifted

into near IR

• Density 2 - 20 / sq arc sec 6 to 12 IFUs in field of regard

• J, H, K bands• IFU fields ~ 1 x 3 arc sec for sky

subtraction, 50 mas spaxels, R = 3000 - 4000, EE > 50% within 50 mas for optimal tip-tilt stars

• Low backgrounds: AO system < 10-20% of (sky + telescope) Need to evaluate which high-z

science could be done with higher backgrounds

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Science requirements summary to date

• Wavefront error 170 nm or better– Need sensitivity study to see how science would fare if

wavefront error were 200 nm

• Relative photometry to 5%• Contrast H 5.5 at 0.5 arc sec, H 13 at 1 arc sec• Astrometry: companions to 5 mas, Galactic Center to

100 as. Need near-IR ADC.• K-band backgrounds: AO system + IFU < 10-20% of

(sky + telescope)– Need sensitivity study to see how high-z science would fare at

higher background levels

• Not yet found a compelling science case for a large contiguous field (i.e., MCAO)

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Instruments & observing mode requirements, to date

• Instruments:– Refining the requirements developed for the proposal– On-axis near-IR imager, field ~ 10 x 10 arc sec, coronagraph– On-axis visible imager (to 0.6 or 0.7 m), field ~ 3 x 3 arc sec,

coronagraph?– Near IR deployable IFU:

• 6 - 12 channels, field of regard TBD

• Field of view ~ 1 x 3 arc sec

• 50 mas spaxels, EE > 50% within 50 mas for optimal tip-tilt stars

• Still need to evaluate optimum spectral resolution

• Observing modes: – Non-sidereal tracking, <10 minute overhead switching between

targets, consider queue or flexible scheduling

NGAO Performance Budget DevelopmentNGAO Performance Budget Development

Dekany, Ghez, Marchis, Max, Liu, Gavel, Flicker, Wizinowich,

Cameron, Lu, Britton, Macintosh, Neyman, Ireland, Olsen,

Bouchez, Law, Bauman, Le Mignant, Johansson, Chin

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Developing Science-based Performance Budgets

• Systems engineering will consider all of the following budgets– Model assumptions– Model/tool validation– Wavefront error vs. sky coverage for 5-7 science cases– Photometric precision in crowded and sparse stellar fields– Astrometric accuracy at the GC and in sparse fields– High-contrast for diffuse debris disks and compact companions– Polarimetric precision for high-contrast observations– Transmission/background/SNR for several science cases– Observing efficiency– Observing uptime

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Performance Budget Development Goals

• Produce a technical report– Describing the major drivers, including experimentally supportive

information, quantitative background, and potential simulation results

• Produce a numerical engineering tool to support future design iterations– Emphasizing abstracted quantitative scaling laws and

interdependencies

• Support science requirements development– Capturing the experience of the science team and reflecting

quantitative underpinning to current limitations

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Wavefront Error and Encircled Energy

• Science Cases– Maintain all cases from the June ‘06 NGAO proposal

• Key Drivers for initial budget– Uncertainty in tomographic reconstruction error

– Uncertainty in sodium laser photoreturn from the mesosphere• Per delivered Watt, as a function of different pulse formats• Requires 50W class lasers to investigate non-linear optical pumping effects

– Uncertainty in multi-NGS tilt tomography efficacy• Not included in original budget development

– Uncertainty in tip/tilt control efficacy with large tip/tilt mirrors

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Wavefront error budgets

• For observations of– TNO multiplicity– Galactic Center– Field galaxies– Io– Nearby AGN– Gravitational Lenses

• During requirements flowdown & initial design, all performance budgets will be used for rapid reevaluation of performance cost/benefit

Example for LGS observation of TNO using two galactic M-dwarfs as tip/tilt stars

Keck Wavefront Error Budget SummaryV R I J H K

m 0.55 0.70 0.91 1.25 1.65 2.20m 16% 31% 17% 30% 24% 22%

/D (mas) 11.3 14.4 18.8 25.8 34.0 45.4

Atmospheric Fitting Error 55 nm 44 Subaps 0.67 0.78 0.87 0.93 0.96 0.98Bandwidth Error 50 nm 74 Hz 0.72 0.81 0.89 0.94 0.96 0.98High-order Measurement Error 58 nm 150 W 0.64 0.76 0.85 0.92 0.95 0.97LGS Tomography Error 60 nm 5 beacon(s) 0.62 0.75 0.84 0.91 0.95 0.97Asterism Deformation Error 22 nm 0.50 m LLT 0.94 0.96 0.98 0.99 0.99 1.00Multispectral Error 25 nm 30 zenith angle, H band 1.00 1.00 1.00 1.00 1.00 1.00Scintillation Error 15 nm 0.37 Scint index, H-band 0.97 0.98 0.99 0.99 1.00 1.00WFS Scintillation Error 10 nm Alloc 0.99 0.99 1.00 1.00 1.00 1.00

118 nmUncorrectable Static Telescope Aberrations 43 nm 64 Acts 0.79 0.86 0.92 0.95 0.97 0.99Uncorrectable Dynamic Telescope Aberrations 15 nm Dekens Ph.D 0.97 0.98 0.99 0.99 1.00 1.00Static WFS Zero-point Calibration Error 20 nm Alloc 0.95 0.97 0.98 0.99 0.99 1.00Dynamic WFS Zero-point Calibration Error 10 nm Alloc 0.99 0.99 1.00 1.00 1.00 1.00Go-to Control Errors 0 nm Alloc 1.00 1.00 1.00 1.00 1.00 1.00Residual Na Layer Focus Change 1 nm 30 m/s Na layer vel 1.00 1.00 1.00 1.00 1.00 1.00DM Finite Stroke Error 16 nm 4.0 um P-P stroke 1.00 1.00 1.00 1.00 1.00 1.00DM Hysteresis 13 nm from TMT 0.98 0.99 0.99 1.00 1.00 1.00High-Order Aliasing Error 18 nm 44 Subaps 0.96 0.97 0.98 0.99 1.00 1.00DM Drive Digitization 4 nm 10 bits 1.00 1.00 1.00 1.00 1.00 1.00Uncorrectable AO System Aberrations 20 nm Alloc 0.95 0.97 0.98 0.99 0.99 1.00Uncorrectable Instrument Aberrations 25 nm Alloc 0.92 0.95 0.97 0.98 0.99 0.99DM-to-lenslet Misregistration (all sources) 15 nm Alloc 0.97 0.98 0.99 0.99 1.00 1.00

68 nmAngular Anisoplanatism Error 0 nm 0 arcsec 1.00 1.00 1.00 1.00 1.00 1.00

Total High Order Wavefront Error 136 nm 0.10 0.24 0.43 0.64 0.77 0.86

Tilt Measurement Error (one-axis): 5.18 mas 63 nm 17.8 mag (mV) 0.49 0.61 0.73 0.83 0.90 0.94Tilt Bandwidth Error (one-axis) 0.63 mas 8 nm 61.0 Hz 0.98 0.99 0.99 1.00 1.00 1.00Tilt Anisoplanatism Error (one-axis) 5.99 mas 73 nm 40.2 arcsec 0.42 0.54 0.67 0.79 0.87 0.92Residual Centroid Anisoplanatism 1.99 mas 24 nm 5 x reduction 0.87 0.91 0.95 0.97 0.98 0.99Residual Atmospheric Dispersion 1.06 mas 13 nm 20 x reduction 0.39 0.44 0.84 0.96 1.00 1.00Science Instrument Mechanical Drift 0.50 mas 6 nm Alloc (0.2 mas) 0.99 1.00 1.00 1.00 1.00 1.00Long Exposure Field Rotation Errors 0.50 mas 6 nm Alloc (0.2 mas) 0.99 1.00 1.00 1.00 1.00 1.00Residual Telescope Pointing Jitter (one-axis) 4.85 mas 59 nm 29 Hz input disturbance 0.53 0.64 0.75 0.85 0.91 0.95

Total Tip/Tilt Error (one-axis) 9.61 mas 116 nm 0.22 0.31 0.44 0.59 0.72 0.82

Total Effective Wavefront Error 179 nm 0.02 0.08 0.19 0.38 0.55 0.71

Sky Coverage Galactic Lat. 30 deg

Corresponding Sky Coverage 5.0% This fraction of sky can be corrected to the Total Effective WFE shown

Assumptions / Parameters

r0 0.165 m at this zenith Wind Speed 13.67 m/s Zenith Angle 30 degTheta0_eff 1.98 arcsec at this zenith Outer Scale 75 m HO WFS Rate 1114 Hz SH using CCDSodium Abund. 4 x 109 atoms/cm2 LGS Ast. Rad. 0.08 arcmin HO WFS Noise 1.7 e- rms

HOWFS anti-aliasing NO Science Target: SCAO LO WFS rate 915 Hz SH using SNAP

LOWFS Star(s): MOAO 2 TT star(s) & 0 TTFA star(s) LO WFS Noise 4.5 e- rms

Tip/Tilt Errors Strehl ratios

Parameter

Parameter

High Order Strehl

WavefrontError (rms)

Strehl RatiosHigh-order Errors (LGS Mode)

Band (microns)

Total Strehl

Tip/Tilt Strehl

AngularError (rms)

EquivalentWFE (rms)

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• Performance versus Blue Book– Delivered system & science instrument didn’t achieve some

requirements

– Environment different than some assumptions

• Why will NGAO performance estimates be better – Experience at Palomar, Lick & Keck

– Better understanding of Keck environment

– Performance estimation tools more complete & anchored to actual performance

• For effects such as multi-guide star tomography for which we don’t have real-world experience:– Based on modeling and detailed simulations

• Comparing & validating these tools (TMT, Gemini, COO, Keck, UCO)

– Aided by lab experiments (e.g. LAO)

– Undoubtedly there will be “real-world” effects that we are not yet taking into account

Improving Performance Predictions

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Keck LGS AO Wavefront Error BudgetExplanations

Blue Book Measured NGAO toolAtmospheric fitting 123 128 102Telescope fitting 105 60 70Camera 35 113 113 NIRC2 aberrationsDM bandwidth 36 157 143 Lower bandwidthDM measurement 98 142 135 Lower laser powerTT bandwidth 34 109 30 Vibrations - will be added to NGAO toolTT measurement 34 23 4LGS focus error 35 36 25Focal anisoplanatism 127 175 151 Different atmosphereLGS high-order error 0 80 80Centroid anisoplanatism 0 0 21Atmospheric dispersion 0 0 81Miscellaneous 0 0 0 Dyn calibs, tel, poorly sensed, atmos dispMiscellaneous (NGAO) 0 0 53 Seven ~20 nm termsCalibrations 30 0 40Total wavefront error 243 358 330K-band Strehl 0.62 0.35 0.41Percentile Seeing 50% 75% 65%

LGS (10th mag)

NGAO Trade StudiesNGAO Trade Studies

Dekany

To date: Bauman, Clare, Gavel, Flicker, Kellner, Neyman, Velur

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Design Trade Studies

• Trade studies were initiated at the start of System Design phase• We have completed or nearly completed:

– Methods of mitigating laser Rayleigh backscatter

– Laser guide star asterism & geometry

– Multi-Object (MOAO) & Multi-Conjugate (MCAO) architectures

– Variable vs fixed laser asterism on the sky

– Fast tip/tilt opto-mechanical implementation options

– Low order wavefront sensor type & number

• Additional design studies now underway include:– LGS wavefront sensor architecture & type

– Science instrument re-use

– Telescope static & dynamic errors

– Interferometer support

– Sodium return versus laser format

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Mitigating Laser Rayleigh Backscatter

• Evaluate impact of unwanted Rayleigh backscatter on NGAO system performance

• Status:– Evaluated the intensity of the Rayleigh as well as aerosol and

cirrus backscatter as seen at the Keck focal plane– Surveyed the available lasers and pulse formats– Surveyed methods of blocking Rayleigh– Interim results at NGAO meeting 3 (12/13/06)

• Best rejection choice: appropriately pulsed laser which can have a gated return so that almost no Rayleigh background is encountered

• However, most powerful & promising lasers in terms of sodium return per Watt, are CW

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LGS Asterism & Geometry

• Find the simplest LGS asterism geometry meeting the performance budget goals– Number of guidestars– Constellation configuration– Constellation size

• Conclusions– Simulations of tomography

generally validate the theoretical scaling laws

– 5 LGS constellation works ok on 20 arcsec field

– 7-9 LGS will be needed on 90 arcsec field

• KAON 429

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MCAO HybridMOAO

Multi-Object vs Multi-Conjugate AO• Understand potential risks, technical challenges, limitations, advantages &

room for improvement with Multi-Object (MOAO) & Multi-Conjugate (MCAO)

• Calculated performance for 1, 2 & 3 DM MCAO systems & compared to small sub-field IFU or imager arms, each with a DM

• Conclusions:– MCAO offers a contiguous field for imaging, but a large error term. “Generalized

anisoplanatism” dominates in wide-field cases– MOAO greatly reduces anisoplanatic error at cost of non-contiguous field

• KAON 452

LGS WavefrontSensors

DeformableMirrorsScience

Instruments

LaserBeams

TomographyComputer

Dichroic



Instruments

LaserBeams

TomographyComputer

Dichroic

LGS Wavefront Sensors

DM

LaserBeams

Tomography Computer

ScienceDetector

ScienceDetector

DM

Dichroic

LGS Wavefront Sensors

DM

LaserBeams

Tomography Computer

ScienceDetector

ScienceDetector

DM

Dichroic



Instruments

LaserBeams

TomographyComputer

Dichroic



Instruments

LaserBeams

TomographyComputer

Dichroic

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Summary

• Management update:– Systems Engineering Management Plan in place– Executive Committee working well together– Ramp up slower than planned, but team & processes now in

place– Good technical progress is being made

• Technical update:– Iterations between science requirements & performance budgets

are achieving our goals of understanding what is really needed– Learning what we need to from architecture trade studies– Building base for design choices & cost/benefit trades

We now have the management structure, plan & enthusiastic team to produce an excellent NGAO System Design.

NGAO System Design Phase Update Peter Wizinowich, Rich Dekany, Don Gavel, Claire Max for NGAO Team SSC Meeting January 24, 2007.

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