MCAOMCAO

Laser Launch Laser Launch TelescopeTelescope

and Periscopeand Periscope

Celine d’Orgeville and Jim Catone

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

• On-axis, behind secondary mirror

• Do not obstruct secondary mirror central hole when MCAO not in use

CoDR: deployable primary mirror

LLTLLT

PDR: PERISCOPE

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOLLT requirementsLLT requirements

Parameter SpecificationMagnification ratio

60 with a 1% tolerance

Field of View+/- 1.2 arcmin (unvignetted)+/- 1.0 arcmin (for image quality spec.)

Optical design No central obscurationNo internal focus~ 450mm STOP

Focus adjustmentFixed afocal telescope (passive comp. preferred)

Optical transmission

> 97 % @ 589nm~ 50 % in the visible (450-700nm)

Optics and coatings

Can sustain power densities in the 500-1000 W/cm2 range

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOLLT image quality analysis for LLT image quality analysis for MCAOMCAO

• LGS WFS centroiding measurement error must not increase by more than 20% (req.)/ 10% (goal)

Low order aberrations• LGS spot size

increase < 10% (5%)• Defocus <0.1

wave rms• Astig <0.18 wave

rms• Coma <0.1 wave rms• Trefoil <0.25 wave

rms• Spherical <0.1 wave

rms

High order aberrations• Decrease in SNR < 10%

(5%)

• High order ab. <0.06 wave rms

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

LLT image quality specs for MCAOLLT image quality specs for MCAO

Wavefront aberrations

Requirement Goal

Tip/Tilt ( dynamic) < 0.1 Hz 0.1-1 Hz 1-30 Hz > 30 Hz

(in arcsec on the sky) < 10’’ peak < 1’’ peak < 0.2’’ peak < 0.03’’ rms

Low order aberrations < 0.15 wave rms < 0.1 wave rms

High order aberrations < 0.06 wave rms < 0.04 wave rms

All other performance being equal, this would save a 15% increase in laser power requirement

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

LLT optical designLLT optical design

16mm toroidal fold mirror

10mm silica aspheric

lens

450mm, f=1672.3mm, 258mm

off-axis parabola

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOOptical perf. over ±1 arcmin FoVOptical perf. over ±1 arcmin FoVfor a uniformly illuminated 450mm for a uniformly illuminated 450mm STOPSTOP

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOOptical perf. over ±1 arcmin FoVOptical perf. over ±1 arcmin FoVfor a uniformly illuminated 300mm for a uniformly illuminated 300mm STOPSTOP

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOEncircled energy over ±1.2 arcmin Encircled energy over ±1.2 arcmin FoVFoV

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOGemini Telescope’sGemini Telescope’sTop End AssemblyTop End Assembly

Mounting SurfaceFor the LLT

Electronics Boxes

f/16 Top End

SecondaryMirror Module

Secondary SupportStructure (SSS)

Top End Vanes

Vane Ring

SSS/M2Interface

Plane

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOGemini Telescope’sGemini Telescope’sSecondary Support Secondary Support

StructureStructure

3D Viewof the SSS

ReferencePlane

475.0

1084.0±7.0

2148.0

2153.0

2348.0

2323.0

2178.0

25.0

• Figures taken from drawings ICR01 and ICR02

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

SSS/LLT/BTOOB AlignmentSSS/LLT/BTOOB Alignment

• First align the BTOOB to the LLT and pin• Remove the BTOOB and loosely install the LLT in the

SSS• Reinstall the BTOOB on the LLT• Align the BTOOB/LLT assembly with the SSS• Remove the BTOOB and pin the LLT/SSS interface• Finally, reinstall the BTOOB

Secondary Support

Structure

Laser Launch

Telescope

Beam Transfer Optics Optical Bench

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

4X LLT/SSS Interface Pad

LLT Top Plate InterfacesLLT Top Plate Interfaces

3X LLT/BTOOB Interface Pad

F910.0

F500.0

2X LLT/SSS Location PinAccess Port

+X

-X

+Y

-Y

2X LLT/BTOOBAlignment

PinLocation

PLAN VIEW

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

LLT Interface DetailsLLT Interface Details

LLT/SSS Alignment LLT/BTOOB Alignment

SSS Top

Plate M20 Nut&

Washer

½” Locating Pin

1.0 mm Raised Pad5.0 mm Thick Shim

BTOOpticalBenchLLT Top

Platew/ M20 Stud

LLT Pilot HoleAccess Port

1.0 mm Raised Pads

¼” Locating Pin

M12 Bolt& Washer

M12 Threaded Insert

15.0

24.0

25.0

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOPassive Focus Passive Focus Compensation Compensation ConfigurationConfiguration

258.0 Off-Axis Distance

1682.31631.5

DETAIL 1

1 Fold MirrorDivergingLens

Incoming Beam

Translation Table

Compensation

RodTheoretical MirrorMounting Plane

Exiting Beam

• Produces a maximum error of 2.5 nm in the temperature range of 0 ± 15°

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOPeriscopePeriscope

• Why ?– 168mm M2 hole to avoid narcissus effect when

observing in thermal IR– M2 hole blocked by LLT, IR instrument can no longer see

sky

• How ?– Two-mirror periscope to divert the beam around the SSS– Mirror cover to block beam during visible observations– Oversized FoV and STOP to allow for M2 tip/tilt and

decentrations and telescope flexures

• Where ?– Bottom of SSS– Replace Gemini central baffle

• Who ?– Gemini designs, integrates and commissions – RFP for parts for GN and GS periscopes

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

Periscope Optical DesignPeriscope Optical Design

180mm Hole in M2(Actual Hole is

168 mm)

Focus Target at Height of BTOOB/LLT Assembly

PM2 ParentMirror

PM1 ParentMirror

8M TelescopeAxis

= 10°±1°

3.5° to 4.5° Exclusion Angle on the Sky

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

Secondary Mirror Bracket

Mirror Cover

Assembly

Primary Mirror Bracket

Primary Mirror

Secondary Mirror

Periscope SubsystemPeriscope Subsystem

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOPeriscope Location (SSS)Periscope Location (SSS)

SSS Cross Bracing

Periscope

Assembly

SSS

Top End Vane Interface

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOPeriscope Location (M2)Periscope Location (M2)

f/16 SecondaryMirror (M2)

M2 PositioningMechanism

M2 Tilt Mechanism

475.035.0

897.0

Beam Path

Periscope Assembly

LLT

168 mm Optical Stop

SSS

M2 Mounting Plate

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAOPeriscope Mirror Periscope Mirror

MountingMounting

115° Offset

Spherical Mount

Secondary

Bracket Flange

PrimaryMirror

Primary Mirror Bracket

Axis of Symmetry

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

Periscope Mirror CoverPeriscope Mirror Cover

Secondary Mirror

Mirror Cover Motor Bracket

Mirror Cover Motor

Aluminum Hinge

Mirror Cover 2-Bar

Linkage

Secondary Mirror Bracket

May 24-25, 2001 MCAO Preliminary Design Review

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MCAOMCAO

Mass AllocationMass Allocation

Total Mass Addedto the SSS125 ±25 kg

BTOOB Mass20 kg

LLT Mass120 kg

Periscope Mass10 kg

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