Transcript Adaptive Optics Update

MCAO
Laser Launch Telescope
and Periscope
Celine d’Orgeville and Jim Catone
MCAO
LLT
• On-axis, behind
secondary mirror
• Do not obstruct
secondary mirror
central hole when
MCAO not in use
 CoDR: deployable
primary mirror
 PDR: PERISCOPE
May 24-25, 2001
MCAO Preliminary Design Review
2
LLT requirements
MCAO
Parameter
Specification
Magnification ratio
60 with a 1% tolerance
Field of View
+/- 1.2 arcmin (unvignetted)
+/- 1.0 arcmin (for image quality spec.)
Optical design
No central obscuration
No internal focus
~ 450mm STOP
Focus adjustment
Fixed afocal telescope (passive comp.
preferred)
Optical
transmission
> 97 % @ 589nm
~ 50 % in the visible (450-700nm)
Optics and coatings
Can sustain power densities in the 5001000 W/cm2 range
May 24-25, 2001
MCAO Preliminary Design Review
3
MCAO
LLT image quality analysis for MCAO
• 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
May 24-25, 2001
High order aberrations
• Decrease in SNR < 10% (5%)
• High order ab. <0.06 wave rms
MCAO Preliminary Design Review
4
LLT image quality specs for MCAO
Wavefront
aberrations
Requirement
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
MCAO
Goal
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
5
MCAO
LLT optical design
16mm toroidal
fold mirror
10mm silica
aspheric lens
May 24-25, 2001
450mm,
f=1672.3mm,
258mm offaxis parabola
MCAO Preliminary Design Review
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Optical perf. over ±1 arcmin FoV
for a uniformly illuminated 450mm STOP
May 24-25, 2001
MCAO Preliminary Design Review
MCAO
7
Optical perf. over ±1 arcmin FoV
for a uniformly illuminated 300mm STOP
May 24-25, 2001
MCAO Preliminary Design Review
MCAO
8
MCAO
Encircled energy over ±1.2 arcmin FoV
May 24-25, 2001
MCAO Preliminary Design Review
9
Gemini Telescope’s
Top End Assembly
Secondary Support
Structure (SSS)
Top End
Vanes
Mounting
Surface
For the LLT
Electronics
Boxes
Vane Ring
f/16 Top
End
SSS/M2
Interface
Plane
May 24-25, 2001
MCAO
Secondary
Mirror
Module
MCAO Preliminary Design Review
10
Gemini Telescope’s
Secondary Support Structure
MCAO
25.0
2348.0
2178.0
2323.0
2148.0
2153.0
1084.0
±7.0
475.0
Reference
Plane
3D View
of the SSS
• Figures taken from drawings ICR01 and ICR02
May 24-25, 2001
MCAO Preliminary Design Review
11
SSS/LLT/BTOOB Alignment
Secondary
Support Structure
•
•
•
•
•
•
Laser Launch
Telescope
MCAO
Beam
Transfer
Optics
Optical Bench
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
May 24-25, 2001
MCAO Preliminary Design Review
12
LLT Top Plate Interfaces
PLAN VIEW
+Y
MCAO
3X LLT/BTOOB
Interface Pad
4X LLT/SSS
Interface Pad
F910.0
-X
+X
F500.0
2X LLT/BTOOB
Alignment Pin
Location
May 24-25, 2001
-Y
MCAO Preliminary Design Review
2X LLT/SSS
Location Pin
Access Port
13
MCAO
LLT Interface Details
LLT Top Plate
w/ M20 Stud
BTO
Optical
Bench
M12 Bolt
& Washer
LLT Pilot Hole
Access Port
1.0 mm Raised Pads
¼” Locating
Pin
15.0
24.0
25.0
SSS Top
Plate
½” Locating Pin
M20 Nut
& Washer
1.0 mm Raised Pad
5.0 mm Thick Shim
LLT/SSS Alignment
May 24-25, 2001
M12 Threaded Insert
LLT/BTOOB Alignment
MCAO Preliminary Design Review
14
Passive Focus Compensation
Configuration
MCAO
258.0 Off-Axis Distance
1
Exiting
Beam
1631.5
1682.3
Incoming
Beam
Translation
Table
Fold
Mirror
Diverging
Lens
Compensation
Rod
Theoretical Mirror
Mounting Plane
DETAIL 1
• Produces a maximum error of 2.5 nm in the
temperature range of 0 ± 15°
May 24-25, 2001
MCAO Preliminary Design Review
15
MCAO
Periscope
• 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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Periscope Optical Design
8M Telescope
Axis
a = 10°±1°
3.5° to 4.5°
Exclusion
Angle on the
Sky
MCAO
Focus Target at
Height of
BTOOB/LLT
Assembly
PM1 Parent
Mirror
PM2 Parent
Mirror
May 24-25, 2001
180mm Hole in M2
(Actual Hole is
168 mm)
MCAO Preliminary Design Review
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Periscope Subsystem
MCAO
Primary
Mirror
Mirror
Cover
Assembly
Primary
Mirror
Bracket
Secondary
Mirror
Secondary
Mirror
Bracket
May 24-25, 2001
MCAO Preliminary Design Review
19
Periscope Location (SSS)
MCAO
SSS
Periscope
Assembly
Top End Vane Interface
May 24-25, 2001
MCAO Preliminary Design Review
SSS Cross
Bracing
20
Periscope Location (M2)
MCAO
SSS
LLT
Periscope Assembly
475.0
35.0
M2 Mounting Plate
M2 Positioning
Mechanism
897.0
168 mm Optical
Stop
May 24-25, 2001
M2 Tilt Mechanism
Beam Path
MCAO Preliminary Design Review
f/16 Secondary
Mirror (M2)
22
Periscope Mirror Mounting
Secondary
Bracket
Flange
MCAO
Axis of Symmetry
Spherical
Mount
Primary
Mirror
Primary
Mirror
Bracket
115° Offset
May 24-25, 2001
MCAO Preliminary Design Review
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Periscope Mirror Cover
Mirror Cover Motor
MCAO
Mirror Cover Motor
Bracket
Mirror Cover
2-Bar Linkage
Aluminum Hinge
Secondary
Mirror
May 24-25, 2001
Secondary Mirror
Bracket
MCAO Preliminary Design Review
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Mass Allocation
MCAO
Total Mass Added
to the SSS
125 ±25 kg
LLT Mass
120 kg
May 24-25, 2001
BTOOB Mass
20 kg
MCAO Preliminary Design Review
Periscope Mass
10 kg
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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
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