1. Introduction of SONG telescope design Guomin Wang, Bozhong Gu, Xiangyan Yuan Zhiyong Zhang, Xiang Jiang, Shihai Yang The Third Workshop of SONG 2010-3-30Beijing

2. Outline:  General requirements.  Structure design introduction.  Conclusions.

3. SONG Optical layout

4. Design specifications Primary mirror diameter: 1.0m; Alt-az mount; Two Nasmyth foci; FOV at Nasmyth focus: 15′; System focal ratio (Nasmyth focus): F/36.7

5. Design specifications M3 is used to direct light to two Nasmyth foci; Distance of M3 above M1: 250mm; Diameter of M3: 206mm; M2 is supported using active positioning system; Diameter of M2: 122mm; Distance between M1 and M2: 2669.926mm; Mount is compatible with the Coude system;

6. Azimuth axis specifications Azimuth rotation range: ±270°(TBD); Slew speed: ＞ 20°/sec; Acceleration/deceleration of rotation: ＞ 2°/s 2 ; Resolution of rotation: ＜ 0.01arcsec;

7. Elevation axis specifications Elevation rotation range: 5°to 89.5°in operation (TBD) 0°to 90°in maintenance Slew speed: ＞ 20°/sec; Acceleration/deceleration of rotation: ＞ 2°/s 2 ; Resolution of rotation: ＜ 0.01arcsec; Blind spot: ＜ 1°;

8. Pointing and tracking specifications Pointing accuracy: ≤ 5″over all sky, ZD ＜ 70°,with pointing model; ≤ 0.5″over 1.5 degree; Tracking accuracy(without AGU): ＜ 1″ RMS over 30min; ＜ 0.3″over 90 sec; First resonance frequency: ＞ 10 Hz;

9. 2. Structure design 4584mm 2460mm 1880mm Baffle style is TBD

10. Animate of telescope

11. Gimbal structure Pier Base Fork Elevation axis Azimuth axis

12. Azimuth axis structure 800×1080×120mm 345×450×110.5mm ERA 880C

13. Basement FEM calculation Max. deformation: 0.0764mm ; Max. stress: 39.9Mpa;

14. Fork structure single part, easy to mount and alignment, and to ensure the position accuracy of elevation axis; welded structure with steel plates; thermal treatment to relieve stress;

15. Fork FEM calculation Max. deformation: 0.0123mm ; Max. stress: 2.36Mpa;

16. Elevation axis structure Bearing Tape encoder Driving motor

17. OSS (Tube) structure Serrurier truss; Primary mirror supporting: vertical: 18-point whiffletree; lateral: counterweight lever;

18. OSS FEM calculation

19. M1-M2 relative offset calculation uy （ mm ） uz （ mm ） rotx (″) 04.53E-05-1.57E-020.00 10-3.07E-02-1.54E-02-0.89 20-6.13E-02-1.47E-02-1.67 30-9.09E-02-1.36E-02-2.34 40-1.18E-01-1.20E-02-2.90 50-1.42E-01-1.00E-02-3.33 60-1.62E-01-7.78E-03-3.65 70-1.77E-01-5.31E-03-3.88 80-1.86E-01-2.71E-03-4.01 90-1.90E-01-5.36E-05-4.05

20. M2 supporting structure 4 vanes connecting to top-ring; Active positioning system: δx, δy, δz, θx, θy; Baffle for stray light;

21. M3 supporting structure 4 vanes connecting to center section; Motorized to achieve rotation for two Nasmyth foci; M3 reducer motor and encoder bearing connecting part to center section

22. Modal calculation ModeFrequency (Hz)Mode shape 131.36Truss lateral 239.14Truss fore-and-aft 348.26Vanes torsion 450.85Fork lateral 552.62Fork fore-and-aft 661.77Fork torsion

23. Control system

24. Conclusions: It is just conceptual design. More detail calculation is needed, such as the motor torque, bearing stiffness, etc. and more innovative structure is needed to improve the performance further. The preliminary structure design and calculation show that the telescope requirements can be met;

25. Thank you !!!