Introduction of SONG

telescope design

Guomin Wang, Bozhong Gu, Xiangyan YuanGuomin Wang, Bozhong Gu, Xiangyan YuanZhiyong Zhang, Xiang Jiang, Shihai Yang Zhiyong Zhang, Xiang Jiang, Shihai Yang

The Third Workshop of SONGThe Third Workshop of SONG2010-3-302010-3-30

Beijing Beijing

Outline:

General requirements.

Structure design introduction.

Conclusions.

SONG Optical layout

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

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;

Azimuth axis specifications

Azimuth rotation range: ±270°(TBD);

Slew speed: ＞ 20°/sec;

Acceleration/deceleration of rotation: ＞2°/s2;

Resolution of rotation: ＜ 0.01arcsec;

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°/s2; Resolution of rotation: ＜ 0.01arcsec; Blind spot: ＜ 1°;

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;

2. Structure design

4584mm

2460mm

1880mm

Baffle style is TBD

Animate of telescope

Gimbal structure

Pier

Base

Fork

Elevation axis

Azi

mu

th

axis

Azimuth axis structure

800×1080×120mm 345×450×110.5m

m

ERA 880C

Basement FEM calculation

Max. deformation: 0.0764mm ;

Max. stress: 39.9Mpa;

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;

Fork FEM calculation

Max. deformation: 0.0123mm ;

Max. stress: 2.36Mpa;

Elevation axis structure

Bearing BearingTape

encoder

Driving motor

OSS (Tube) structure

Serrurier truss; Primary mirror supporting: vertical: 18-point whiffletree; lateral: counterweight lever;

OSS FEM calculation

M1-M2 relative offset calculation

uy （ mm） uz （ mm） rotx (″)

0 4.53E-05 -1.57E-02 0.00

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

-0. 2

-0. 15

-0. 1

-0. 05

0

0. 05

0 10 20 30 40 50 60 70 80 90

el evati on angl e(degree)

uy(m

m)

-0. 018

-0. 016

-0. 014

-0. 012

-0. 01

-0. 008

-0. 006

-0. 004

-0. 002

00 10 20 30 40 50 60 70 80 90

el el vati on angl e(degree)

uz(m

m)

-4. 50

-4. 00

-3. 50

-3. 00

-2. 50

-2. 00

-1. 50

-1. 00

-0. 50

0. 00

0. 50

0 10 20 30 40 50 60 70 80 90

el evati on angl e(degree)

rotx

(arc

)

M2 supporting structure

4 vanes connecting to top-ring; Active positioning system: δx, δy,

δz, θx, θy; Baffle for stray light;

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

Modal calculation

Mode Frequency (Hz) Mode shape

1 31.36 Truss lateral

2 39.14 Truss fore-and-aft

3 48.26 Vanes torsion

4 50.85 Fork lateral

5 52.62 Fork fore-and-aft

6 61.77 Fork torsion

Control system

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;

Thank you !!!Thank you !!!