Gemini AO Program October 21, 1999Gemini Science Committee1 The Gemini Adaptive Optics Program MCAO for Gemini-South Gemini Adaptive Optics Team B. Ellerbroek

October 21, 1999 Gemini Science Committee 1

Gemini AO Program

The Gemini Adaptive Optics The Gemini Adaptive Optics ProgramProgram

MCAO for Gemini-SouthMCAO for Gemini-South

Gemini Adaptive Optics TeamB. Ellerbroek and F.Rigaut


Gemini AO Program

Top Level Perf. Requirement Top Level Perf. Requirement #2#2

“ Image quality of better than 0.1 arcsec with AO:Achievement of outstanding image quality will have the highest scientific priority for the project […]”

• The proposed evolution of the program at CP will enable unique NGST-class scienceenable unique NGST-class science 4 years ahead of NGST launch. It will keep Gemini competitive during the NGST era.


Gemini AO Program

AO and ScienceAO and Science

AO is a rather new domain...– First AO instrument for astro. -> Come-on, ESO 1990– UH curvature system, Mauna Kea 1992– 1994-1998: Exponential progression of # of systems

…but science is already flowing:– Number of Astro paper is growing exponentially– Total of 70+ refereed papers (lost count). Highlights:

Discovery of an asteroid satellite, wrap of Pic disk, Surface and orbital parameters of solar system bodies, YSO disks and outflows (e.g. HL and GG Tau), Stellar motions in GC, Stellar multiplicity surveys, Structure in AGNs, Galaxy dynamic (e.g. CFHT AOSIS), etc...


Gemini AO Program

• 1989: First AO images w/ Come-On (OHP & ESO) 110mas

A short history of astronomical A short history of astronomical AOAO

• 1992: First Curvature system (UH) 70mas• 1996: First Facility system (CFHT AOB)


Gemini AO Program

CFHT Pueo 1996Galactic Center2.2 m

FWHMFWHM

130 mas130 mas


Gemini AO Program

A short history of astronomical A short history of astronomical AOAO

• 1989: First AO images w/ Come-On (OHP & ESO) 110mas• 1992: First Curvature system (UH) 70mas• 1996: First Facility system (CFHT AOB)

• 1996: First compensation in the visible (Mt Wilson) 58mas• 1996: First LGS systems• 1998: LGS systems getting closing expectations• 1999: First h.order system on a large telescope (Keck)

40mas


Gemini AO Program

Keck AO System1999Vesta 1.5 m

FWHMFWHM<40 mas<40 mas 1’’


Gemini AO Program

Gemini’s Gemini’s DedicationDedication

Courtesy C.Roddier, UH-IfA


Gemini AO Program

ALFA AO ResultsALFA AO Results(18 Modes, 0.9-1.0’’ seeing, K band)(18 Modes, 0.9-1.0’’ seeing, K band)

NGS AO• 0.42 Strehl

• 0.53 predicted

Open loop

Loop closedwith LGS AO• 4 W dye laser

• 0.23 Strehl

• FWHM dif-fraction limited.


Gemini AO Program

Where is AO standing ?Where is AO standing ?

• AO technology for astronomy is maturing rapidly– Well designed and calibrated NGS AO systems (CFHT

Pueo, Hokupa’a, MIT/Lincoln Laboratory, SOR) now closely approach their performance predictions.

– Rayleigh beacon LGS AO programs (MIT/LL, SOR) have been technically successful

– Astronomical sodium beacon LGS AO systems have progressed from Strehls of 0.03 to 0.30 in two years

– Sodium layer variability has been well characterized by numerous LIDAR campaigns


Gemini AO Program

Proposed Baseline AO Proposed Baseline AO ProgramProgram

NORTH

SOUTH

1999

2000

2001

2002

2003

2004

SubaruSubaruKeckKeck

VLTVLT VLT-LGSVLT-LGS CP AOS/LGSCP AOS/LGS

AltairAltair10W LGS10W LGS

Hokupa’aHokupa’a 3636 8585

2W LGS2W LGS

CP Hokupa’aCP Hokupa’a 8585


Gemini AO Program

Baseline Program: AltairBaseline Program: Altair

CP AOS/LGS

10W LGS

NORTH

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

Altair

•Progresses well (CDR 02/99)•Statement of work for Altair LGS upgrade nearly ready


Gemini AO Program

Baseline Program: 10W Baseline Program: 10W LGSLGS

CP AOS/LGS

10W LGS

NORTH

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

10W LGS10W LGS

•10 W Laser RFP to go out early October•Power requirements vary from 7 to 23W depending on laser pulse format•Design of the LLT and BTO underway


Gemini AO Program

Baseline Program: MK-Baseline Program: MK-Hokupa’aHokupa’a

CP AOS/LGS

10W LGS

NORTH

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

Hokupa’aHokupa’a 3636 8585

•Hokupa’a-36 installed on the telescope early June this year•Images fully compatible with expectations (seeing ok but not exceptional), near diffraction limit in K band w/ Strehl ~ 15-30%. Great tool for telescope engineering•85 Actuators upgrade to be done next year by UH team on UH/NSF internal funds. Small transferred field (30’’)

Performance w/ NGS (AO only) (2 fold vs 36 actuators):Seeing Strehl(J) Strehl(K)0.45’’ 50% 80%0.65’’ 25% 62%


Gemini AO ProgramCerro PachonCerro Pachon-AOS/LGS -AOS/LGS ForumForumApril 1999, Review Panel April 1999, Review Panel RecommendationsRecommendations1 The IGPO should develop a strategy for its overall adaptive optics program which satisfies the

Gemini community. Timing of the program, staff resources, and cost must be addressed. The RP also notes that the experience gained with the Altair AO and Hokupa'a teams are valuable to the overall program and should be folded into the planning.

2 The Project should conduct a significant but time-limited study of a multiconjugate adaptive optics system for Cerro Pachon. This would provide an exciting advancement in capabilities but implementing the system should be conditional on "filling" the AO gap on Gemini-South and addressing the requirements of the coronagraphic imager. The study should address the theoretical analysis, science drivers, technical challenges, systems engineering, and programmatics of such an AO system. With the development of a plan, the RP recommends that Gemini adopt as aggressive a schedule as possible to bring this capability to the community.

3 The IGPO should lead the conceptual design program of the Gemini-South AO system, including defining the allocation of subsystems across the Gemini Community

4 In light of the proposals presented for turn-key laser systems, the RP recommends that the IGPO explore with LiteCycles the manufacture of a Sum Frequency laser. To reduce cost and risk for the laser, procurement through a consortium should be explored, including Keck, and possibly other groups if they can participate on timescales which are consistent with Gemini's schedule for laser deployment.

5 The project should avoid relying on major technological developments such as MEMs, liquid crystals, and other 'advanced' DMs for the CP AOS


Gemini AO Program

Baseline Program: CP-Baseline Program: CP-Hokupa’aHokupa’a

CP AOS/LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

2W LGS2W LGS


• AOAO: Duplicate of the MK upgrade of Hokupa’a to 85 actuators. UH AO Team. Proposal submitted to NSF 08/99. Optomechanical upgrades (FoV 60’’) + LGS compatible

Performance w/ NGS (AO only):Seeing Strehl(J) Strehl(K)0.45’’ 50% 80%0.65’’ 25% 62%

• LGSLGS: Off-the-shelf 2W CW laser. Coherent/Spectra physics CW 10W pump laser + ring dye laser (demonstrated in lab)• IR ImagerIR Imager: ABU


Gemini AO Program

Baseline Program: CP-Baseline Program: CP-Hokupa’aHokupa’a

CP AOS/LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

2W LGS2W LGS


Rationale:Rationale:• Gives us a 2+ year window of unchallenged AO+LGS capability unchallenged AO+LGS capability in the southern hemispherein the southern hemisphere (comp. NAOS) w/ Adequate JHK performance. • Build expertise on LGS by stepping up gradually (Laser Launch Telescope + Beam Transfer Optics)• Getting AO on CP as soon as possible relieves pressure, allowing us to avoid the rush and do a better job on the final CP system


Gemini AO Program

Baseline Program: Facility CP Baseline Program: Facility CP AOSAOS

CP AOS/LGS

10W LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

Context:Context:• Simplest case = duplicate Altair -> No AO facility until late 2002.• Other observatories have very capable AOSs in the north (Keck 1999) and in the south (VLT-NAOS 2001) -> Competitiveness issue

Rationale:Rationale: (Why?)(Why?)• Provide the Gemini community with NGST-like capabilities (spatial res. and field), matching the Gemini science goals and instrumentation• Sets up Gemini to be a lead ground-based facility in the NGST era with matching resolution and similar field of view• Future ELTs require “wide” field of view AO

CP AOS/LGSCP AOS/LGS


Gemini AO Program


CP AOS/LGS

10W LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

Proposal:Proposal: (What?)(What?)• Build a high performance, 2 arcminutes field of view AOS with homogeneous PSF quality over the entire field of view, with very high sky coverage

How ?How ?• Using Multi-Conjugate AO, i.e. 4-5 LGSs and wavefront sensors to measure the turbulence in 3D and 2-3 deformable mirrors to correct it• This uses currently available technology. NO hardware development required other than lasers (same as MK-LGS)



Gemini AO Program

What is Tomography ?What is Tomography ?1. Cone effect1. Cone effect

90 k

m


Gemini AO Program

What is tomography ?What is tomography ?2. Multiple guide star and 2. Multiple guide star and tomographytomography

90 k

m


Gemini AO Program

What is multiconjugate?What is multiconjugate?


Gemini AO Program



Gemini AO Program


Telescope

DM1 DM2

Turb. Layers#1 #2

Atmosphere

WFS

UP


Gemini AO Program


CP AOS/LGS

10W LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

What does MCAO do that another system wouldn’t ?What does MCAO do that another system wouldn’t ?• Sky coverage (50%) increased (50-500x) w/ respect to a NGS system• Increased performance on axis w/ respect to a LGS system because the cone effect is taken care of• Increased field of view (well matched to IRMOS)• Uniform PSF across the FoV -> Easier and more accurate Data Reduc.



Gemini AO Program

Classical AO

MCAO

No AO

165’’

MCAO Performance MCAO Performance SummarySummaryEarly NGS results, MK ProfileEarly NGS results, MK Profile

2 DMs / 5 NGS

320 stars / K band / 0.7’’ seeing

1 DM / 1 NGS

Stars magnified for clarity


Gemini AO Program

MCAO Performance MCAO Performance SummarySummaryEarly NGS results, MK ProfileEarly NGS results, MK Profile

Classical AO

MCAO

Guide star location


Gemini AO Program


CP AOS/LGS

10W LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

PerformancePerformance

Mode %Sky3 SRJ(0’’) SRJ(48’’) FOV HardwareNGS 1% 0.55 0.04 30’’ 1 1DMLGS 17% 0.47 0.04 32’’ 1 1DM/1LGSMCAO 34% 0.54 0.35 2’ 2 3DM/5LGS

1 50% Strehl ratio attenuation2 limited by the AO-Fold aperture3 Sky coverage at galactic pole



Gemini AO Program


CP AOS/LGS

10W LGS

SOUTH

1999

2000

2001

2002

2003

2004

SubaruKeck

VLT VLT-LGS

Hokupa’a 36 85

2W LGS

CP Hokupa’a 85

SOUTH

Where are we?Where are we?• Feasibility studyFeasibility study progressing, including:

•First pass on the science drivers•Theoretical analysis of MCAO control/numerical simulations/Performance assessment•A proof-of-concept optical and mechanical layout•Assessment of the need in computing issues•Management plan including schedule and resource needs



Gemini AO Program

MCAO for Gemini-SouthMCAO for Gemini-SouthPerformance, Feasibility, and SchedulePerformance, Feasibility, and Schedule

• A multi-conjugate AO system for Gemini-south can theoretically provide highly uniform turbulence compensation over a 1-2’ diameter field-of-view

• System can be implemented with largely existing hardware and technology– Fully acceptable deformable mirrors, tip/tilt mirrors,

and wave front reconstructs have been demonstrated– Most recent high-speed 1282 CD's meet wave front

sensor requirements with margin– Significant improvements still required in sodium laser

power and reliability• Comparable with conventional LGS AO on a per

beacon basis• Estimated schedule for science handover is spring 2004


Gemini AO Program

NGS, LGS, and Multi-conjugate NGS, LGS, and Multi-conjugate AOAOPerformance CharacteristicsPerformance Characteristics

•T/T guide star brightness (relaxed)• TBD (new inverse problem)

•T/T guide star brightness (relaxed)• Tilt anisoplanatism• Cone effect

• Guide star brightness• Common anisoplanatism

Fundamental limits

1-2’(Nearly uniform)

20-40”(Nonuniform)

20-40”(Nonuniform)

Compensated field-of-view

Further improved (~34% at galactic

pole)

Good (~17% at galactic pole,SR=0.6 in H)

Poor (0.1-2%)Sky coverage

MCAOLGS AONGS AO

• Sky coverage and field-of-view are for J, H, K bands with 0.5 arc second seeing


Gemini AO Program

Analysis and Simulation Analysis and Simulation ModelsModels

• Two approaches available for more detailed modeling of MCAO– Upgraded simulation– Statistical analysis based opon turbulence statistics,

MCAO system parameters• Both approaches treat laser- and natural guide stars,

WFS/DM geometries, CP turbulence profiles– Analysis derives “optimal” wave front reconstructors– Simulation more efficient for standard least-squares

approach• Both approaches extendable to model WFS noise, servo lag,

telescope/instrument aberrations– Simulation can potentially model wave optics effects in

wave front sensors and the atmosphere


Gemini AO Program

MCAO Parameters for MCAO Parameters for Gemini-CPGemini-CP

• 4 or 5 laser guide stars– 30 to 60” (48”) offset from optical axis– 10 to 20 Watts CW equivalent power, 1.5 XDL

• 4 or 5 LGS wave front sensors– 12 by 12 or 16 by 16 subapertures– 80 by 80 to 128 by 128 pixels– 5 to 10 read noise electrons, 500 to 1000 Hz sampling

• 2 or 3 deformable mirrors– 13 or 17 actuators across beamprint– Conjugate ranges of 0, 4-4.5, 8-9 km

• 3-4 T/T or T/T/F natural guide stars, 1 T/T mirror

(Parameters Used for Following Sample Results) (Parameters not Yet Modeled)


Gemini AO Program

Sample Numerical ResultsSample Numerical Results

• 0 degree zenith• 50% seeing• 12 by 12 NGS (black)• 12 by 12 MCAO (red)• 16 by 16 MCAO (blue)• I, J, H, and K bands

K

H

J

I


Gemini AO Program

Sample Numerical ResultsSample Numerical ResultsVariation with Seeing and Zenith Variation with Seeing and Zenith AngleAngle0 Degree Zenith 45 Degree Zenith

• 12 by 12 NGS (black), 12 by 12 MCAO (red), and 16 by 16 MCAO (blue)• I, J, H, and K spectral bands


Gemini AO Program

Sample ResultsSample ResultsSlit Coupling Efficiency at 0 Degrees ZenithSlit Coupling Efficiency at 0 Degrees Zenith

•16 by 16 MCAO, I, J, H, and K spectral bands

• Horizontal and vertical 0.1 arc second slits


Gemini AO Program

Why Multiple Tip/Tilt NGS’s?Why Multiple Tip/Tilt NGS’s?

– Consider a turbulence profile with a focus aberrations at two ranges (blue)

– LGS measurements (yellow) cannot determine range of the aberration

• Tip/tilt information lost• Equal focus measurement

from each LGS, regardless of aberration range

– Tip/tilt NGS measurements can determine range from the differential tilt between stars

– Three tip/tilt NGS’s needed for all three quadratic modes

– Alternate approaches: Rayleigh LGS’s, or a solution to the LGS tilt indeterminacy problem

r)=ar2

r)=a(cr+d)2

=ac2r2+2acdr+ad2

~ ac2r2

After tilt removal


Gemini AO Program

MCAO Sky Coverage with MCAO Sky Coverage with Multiple Tip/Tilt NGSMultiple Tip/Tilt NGS

• Quantitative sky coverage calculations more complex than for conventional AO, but some initial estimates are possible– Only one NGS need be sufficiently bright for correction

of high-bandwidth, wind-shake induced tip/tilt jitter– The atmospheric modes corrected by remaining

reference stars are lower frequency, allowing lower control bandwidths and dimmer stars (e.g. 30Hz sampling rate)

– Preliminary calculation for the galactic pole:• LGS AO sky coverage for 60% Strehl in H: 17%• MCAO coverage with 1 m=18 star and 2 m=20

stars within 1’ radius: 34%


Gemini AO Program

MCAO Implementation-MCAO Implementation-Feasibility study conclusions:Feasibility study conclusions:

• Optics and optics bench– Mass, volume similar to Altair

• Wave front sensor camera– Goal of a single camera for all laser guide stars– 80 by 80 to 128 by 128 pixels, 5 to 10 read noise

electrons• Deformable mirrors and tip/tilt mirror

– Number of actuators, other parameters demonstrated• Wave front reconstruction electronics

– Frame rate, number of inputs/outputs demonstrated• Tip/tilt sensors, laser transfer optics and launch telescope

– Appear straightforward, feasibility designs in progress– 2-3 T/T sensors + 1 more provided by OIWFS

• Laser(s): Technology and engineering development required


Gemini AO Program

MCAO Science Optical PathMCAO Science Optical Path

•3 DM’s at R=0, 4, and 8 km 3 DM’s at R=0, 4, and 8 km •13 actuators across beamprint13 actuators across beamprint•4 folds, 2 off-axis parabolas,4 folds, 2 off-axis parabolas, 1 dichroic beamsplitter (not shown)1 dichroic beamsplitter (not shown) - Near-minimum number of surfaces for - Near-minimum number of surfaces for facility MCAOfacility MCAO• f/30 output focusf/30 output focus


Gemini AO Program

MCAO LGS Optical PathMCAO LGS Optical Path

4 LGS’s sensed with 1 WFS CCDZEMAX optical schematic

• Outgoing: Single launch telescope for all guide stars

• Return: One WFS camera for all guide stars


Gemini AO Program

WFS Camera OptionsWFS Camera Options

Supports 5 LGS,

16 by 16 SA1000+6-10128 by

128

MIT/LL CCD

1-2 Cameras for 4-5 LGS, 12 by 12 SA

1000580 by 80EEV CCD

500-10005-10

80 by 80to

128 by 128Requirement

CommentsFrame

rate, Hz

Read noise

electronsPixels

• MIT/LL read noise level is new information since feasibility study


Gemini AO Program

Approach to Multiple Tip/Tilt Approach to Multiple Tip/Tilt NGS WFS’sNGS WFS’s

X stage

Y stage

200mm

To APDs

X stage

Focal plane

• Fiber-fed APD quadrant detectors

•2 or 3 T/T WFS’s in AO instrument package

• One additional T/T/F WFS in each facility instrument, for a total of 3-4 sensors


Gemini AO Program

Laser IssuesLaser Issues

• Power requirement:– Equivalent to conventional LGS AO on a per beacon basis– 20-40 Watts per LGS, 80-200 Watts total for short pulse,

flashlamp+Nd:YAG-pumped dye lasers (LLNL)• ~20 Watts demonstrated• Scaling a cost/engineering issue (electrical power,

heat dissipation, flammable dye)– 7-12 Watts per LGS, 28-60 Watts total for diode-pumped,

Nd:YAG sum frequency lasers (MIT/LL and others)• ~5 Watts demonstrated• Scaling a technical issue (Nd:YAG beam quality and

sum frequency feasibility at higher powers)


Gemini AO Program

Baseline ScheduleBaseline Schedule

• Conceptual design review: 3/00

• Preliminary design reviews: 12/00

• Critical design reviews: 12/01

• Subsystems complete: 6/03

• System integration and test: 10/03

• Science handover: 3/04

ID Task Name Duration

1 CP LGS MCAO System 1632 days

2 Conceptual Design 632 days

3 CP Sight Characterization 261 days

4 Science and System Implimentation Review 65 days

5 CoD Forum 1 day

6 Review Forum 22 days

7 System Concept Development 152 days

8 System Requirements Review (Gemini Board) 1 day

9 System Conceptual Design 87 days

10 Conceptual Design Review 0 days

11 Subsystem Requirements and Interface Description 44 days

12 AO Instrument Package 799 days

13 Preliminary Design Phase 141 days

14 Preliminary Design 140 days

15 Lab Demo 140 days

16 Integration and Test Planning 120 days

17 Preliminary Design Review(s) 1 day

18 Detailed Design Phase 258 days

19 Subsystem Detailed Design 257 days

20 Integration and test planning 160 days

21 Critical Design Review(s) 1 day

22 Fabrication Phase 400 days

23 Fabrication of Subsystems 300 days

24 I, T, & C Proceedures 200 days

25 Operational Software Implementation 300 days

26 Integration and Test 100 days

27 Laser System 799 days

28 Preliminary Design Phase 141 days

29 Preliminary Design 140 days


31 Preliminary Design Review(s) 1 day

32 Detailed Design Phase 258 days

33 Subsystem Detailed Design 257 days

34 Risk Reduction Prototyping 257 days


36 Critical Design Review(s) 1 day

37 Fabrication Phase 400 days

38 Fabrication of Subsystems 300 days

39 I, T, & C Proceedures 200 days

40 Operational Software Implementation 300 days

41 Integration and Test 100 days

42 System Integration Phase 201 days

43 System Integration and Test 100 days

44 Commissioning 100 days

45 Science Handover 1 day

3/31

12/14

12/11

12/14

12/11

O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M A M J J A S O N D J F M2000 2001 2002 2003 2004


Gemini AO Program

Gemini AO Program: Gemini AO Program: Division of Work within Division of Work within PartnershipPartnership

Gemini AO program ambitious, but IGPO is not proceeding alone

• Partnership Workload (including vendors):– Hokupa’a-85 for Gemini-North: UH– Hokupa’a-85 for Gemini-South:

• WFS and DM: UH• Commercially supplied dye laser

– Altair: HIA– Altair LGS:

• WFS upgrades: HIA• Laser source: Contract

– Coronograph AO: Instrument supplier• Common infrastructure (IGPO): LGS transfer optics, launch

telescope, and safety system• MCAO is the focus of IGPO efforts. Outsourcing of work

expected after CoDR.

Documents

Gemini AO Program October 21, 1999Gemini Science Committee1 The Gemini Adaptive Optics Program MCAO for Gemini-South Gemini Adaptive Optics Team B. Ellerbroek