prime focus option (ming liang) actuator intro/overview/status prime focus slides from m. liang...
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Prime Focus Option (Ming Liang)Prime Focus Option (Ming Liang)Actuator Intro/Overview/StatusActuator Intro/Overview/Status
Prime focus slides from M. Liang (NOAO)M. Sholl
University of California at BerkeleySpace Sciences Laboratory &
Lawrence Berkeley National Laboratory20 November 2009
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Prime Focus Option 1Prime Focus Option 1Designs by Ming Liang (NOAO)Designs by Ming Liang (NOAO)
From Ming Liang
CurvedFocal
Surface
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Prime Focus Option 3Prime Focus Option 3Designs by Ming Liang (NOAO)Designs by Ming Liang (NOAO)
From Ming Liang
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Prime Focus OptionPrime Focus Option
• Pros— No secondary mirror!
— Simplified baffling (no sneak paths to focal plane, see Sholl Optics & Requirements talk from previous session)
— Fiber view camera may be closer
• Cons— Curved focal plane
• Corrected Ritchey Chretien design has flat focal surface
— Harnessing and fibers must be routed through telescope pupil
— Corrector/ADC has six elements• Magnification function shifted from M2 to corrector
— Focal plane and actuator mass supported by prime focus structure
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LAMOST Telescope Fiber Actuators & Fiber LAMOST Telescope Fiber Actuators & Fiber Alignment VerificationAlignment Verification
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Fiber Measurement System CharacterizationFiber Measurement System Characterization
• CCD distortion calibrated with “standard plate”— Standard plate (upper right)
with 784 precision-spaced holes, back-illuminated
— 4096x4096 CCD, 6m from focal plane
— 6m separation on LAMOST and BigBoss (closer with prime focus option)
— Focal plane divided into 16 parts, with overlaps
— Measurement precision (accuracy) 0.013mm
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Fiber View Camera FOV Too Small?Fiber View Camera FOV Too Small?
• CCD Pan Head (Jin, Proc. SPIE Vol. 62693B-1)
• Small focal plane measurement system.
• Solution for CCD that is too small to measure entire focal plane
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Status of Actuator DesignsStatus of Actuator Designs
• Professor Chao Zhai (USTC) to provide details on LAMOST actuator
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Lamost 25.6/33 Actuator DesignLamost 25.6/33 Actuator Design
• Hongzhuan Hu, Prof., Precision Machine and Precision Instrument Department, USTC
• Real, working hardware, meets LAMOST performance requirements!
• 25.6/33mm
• Stepping motors and electrical zero
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LBNL/Ghiorso 19.2mm GTC ActuatorLBNL/Ghiorso 19.2mm GTC Actuator
• R-θ design
• DC Brush motor
• Magnetic encoder
• Very fast! (<10s)
• SPIE paper
• Performance verification underway
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New 15/18mm Actuator (Hu)New 15/18mm Actuator (Hu)
• Theta-Theta stepper drive• USTC expects performance to be
similar to LAMOST actuators (not verified yet)
• Eccentric axis connected directly to output of gearmotor
• No electrical zero• Testing with CCD camera
underway
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Smaller actuators?Smaller actuators?
• Bill Ghiorso presented a concept for a 11mm pitch actuator on 20 May 2009— Theta-theta arrangement
— Only one output gear or pulley set used for second rotation
— 8mm motor features• DC brushed servomotor
• Encoder with index pulse
• Anti-backlash gearhead
— Fiber held by bearing. Does not “wind up.”
— Rotation limited by hard stop (370º)
— Arm travel limited to 190º
• USTC now has a design for a 10mm actuator (Hongzhuan Hu, designer, Prof. Zhai to present)
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Actuator Status & Paths ForwardActuator Status & Paths Forward• USTC (Hu) 25.6mm θ-θ actuators (too large for BigBoss)
— Successful design/fabrication effort— Stepper motor, actuators run slowly (9min center-edge-center)
• LBNL (Ghiorso) 19.2mm R-θ actuator (Ghiorso) (too large for BigBoss)— Prototype built (SPIE 7018-205_4)— Brush DC servomotor and magnetic encoder— Very fast (20s reconfiguration)— W. Ghiorso to comment on testing status
• USTC (Hu) 15mm θ-θ actuator (too large for BigBoss)— Requires fiber precision and accuracy verification (underway)— Stepper motor
• LBNL (Ghiorso) 11mm θ-θ actuator concept— Has design. Modify/Build/fab/test?
• USTC (Hu) 10mm θ-θ actuator— Chao Zhai to present details at this session