optical and infrared telescope fundamentals
TRANSCRIPT
Optical and Infrared
Telescope Fundamentals
Peter WizinowichDunlap Summer School – 26 July, 2018Ethan Tweedie Photography
Pre-Keck
2
Keck Staff
3
Telescope Design Considerations
• Science goals
– Type of science, science instruments
• Performance
– Image quality, angular resolution, field of view,
wavelength coverage, throughput, background,
observing efficiency
• Cost & Schedule
4
Performance
Image Quality Error Budget
5
Image Quality
Optics Environment Other
Optical Figure (M1, M2, M3)
Optical Alignment
Instrument Optics
Atmospheric Seeing
Dome Seeing
Wind Shake
Vibrations
Active Control System Noise
Scattered Light
Sky & Thermal Background
Maunakea
6
7
Dennis Crabtree, 2018
Some Optics Basics
Human Eye
9
Resolution & Sensitivity Gains
10θ ~ λ/r0 λ/D
Diffraction-limited Imaging
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0
0.2
0.4
0.6
0.8
1
0 0.05 0.1 0.15 0.2 0.25
Stre
hl R
atio
RMS Wavefront Error (waves)
Perfect Keck image
SR=0.62 SR=0.25
Optical Aberrations - Phase
12
Optical Aberrations - Image
13
14
Optical Aberrations - Distortion
15
Keck Telescope Optics
Telescope Error Budget
17
1818
Telescope Alignment
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20
Scott Foundation 21
Glass Fabrication
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0
100
200
300
400
500
0 1 2 3 4 5
Sph
ere
, z (
mm
)
S (m)
-2.0
-1.5
-1.0
-0.5
0.0
0 1 2 3 4 5Pa
rab
ola
-S
ph
ere
, ∆z
(mm
)
S (m)
Primary Mirror Focus
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Sphere z = 𝑟 − 𝑟2 − 𝑆2
r = 35 m for Keck
Material to be removed =
Parabola 𝑧 =𝑆2
2𝑟- Sphere
Sphere
z
S
r
f
Focal length f = r/2
Polishing
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Optical Testing
25
Ion Figuring
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Primary Mirror Segment
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Segment Support
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Mirror Segment
Axial Insert
Axial Flex Rod
Inner or Outer Whiffletree Tripod
Secondary Whiffletree Beam
Primary Whiffletree Beam
Actuator
Radial Support Pad
Radial Pad Flexure
Radial Flex Ring
Diaphragm
Radial Post
Mirror Segment Subcell
Telescope Mirror Cell
Primary Mirror Segment
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30
Large
Monolithic
Mirrors
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Large
Monolithic
Mirrors
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33
34
Shack Hartmann Wavefront Sensor
35
f
Telescope Alignment
• Segment tilts
• Secondary piston & tilt
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Segment Warping
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Segment Warping
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39
Segment Phasing
Science Instruments
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41
Dome Design
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43
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The Future
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Keck Opportunities• Akamai• AstroTech• Keck Visiting Scholars• Postdoc Positions
46
Questions?
Adaptive Optics at
Keck Observatory
K1: OSIRISK2: NIRC2
K2: NIRSPEC
ElevationRing
Enclosure withroof removed
AO Optics Bench
Rails to deck
NasmythPlatform
ElectronicsRacks
AO Enclosure
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Light from Telescope
NIRC2
NIRSPEC
1 meter
Keck II AO Bench
Keck I AO Bench
50
OSIRIS
AO Bench
Keck II Laser(2016)
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Keck II Laser Launch Telescope
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Launch
Telescope
Keck AO Science
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Keck LGS
HST
Keck II Near-Infrared
Wavefront Sensing with
NIRC2 Vortex
& NIRSPEC Fiber Injection
Pyramid WFS & Fiber Injection
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Optical FeedFi
ber
Ext
ract
ion
U
nit
(FE
U)
NIRC2 Vortex Coronagraph
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Pyramid & Fiber Injection Layout
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1 meter
FIU Plate
PWS Plate
FSM Assembly
Near-IR Pyramid Wavefront Sensor
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Near-IR Pyramid
Wavefront Sensor
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Ethan Tweedie Photography
Other Keck AO
Developments
Star = PSF PSF-R Difference
On-axis PSF Demo
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Point Spread Function
Reconstruction
Profiler
New Keck II Real-time Controller
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Keck All sky Precision AO (KAPA)
• Laser tomography
– TOPTICA laser
– Asterism generator
– New WFS camera
– New RTC
• Near-IR tip-tilt
– Multiple NGS
• PSF-R for OSIRIS
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Ethan Tweedie Photography
Thanks / Merci