Prime Focus Option (Ming Liang) Actuator Intro/Overview/Status Prime focus slides from M. Liang (NOAO) M. Sholl University of California at Berkeley Space Sciences Laboratory & Lawrence Berkeley National Laboratory 20 November 2009

2 Prime Focus Option 1 Designs by Ming Liang (NOAO) From Ming Liang Curved Focal Surface

3 Prime Focus Option 3 Designs by Ming Liang (NOAO) From Ming Liang

4 Prime 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

5 LAMOST Telescope Fiber Actuators & Fiber Alignment Verification

6 LAMOST Reflective Schmidt Telescope

7 Focal Plane

8

9 Note: fiber/harness bundle

10 Integrated Focal Plane

11 Fiber Position Verification system

12 Fiber 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

13 Fiber View Camera FOV Too Small? CCD Pan Head (Jin, Proc. SPIE Vol B-1) Small focal plane measurement system. Solution for CCD that is too small to measure entire focal plane

14 Status of Actuator Designs Professor Chao Zhai (USTC) to provide details on LAMOST actuator

15 Lamost 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

16 LBNL/Ghiorso 19.2mm GTC Actuator R-θ design DC Brush motor Magnetic encoder Very fast! (<10s) SPIE paper Performance verification underway

17 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

18 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)

19 Actuator 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 _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