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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LAMOST Reflective Schmidt TelescopeLAMOST Reflective Schmidt Telescope

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Focal PlaneFocal Plane

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Focal PlaneFocal Plane

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Focal PlaneFocal Plane

Note: fiber/harness

bundle

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Integrated Focal PlaneIntegrated Focal Plane

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Fiber Position Verification systemFiber Position Verification system

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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