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Conceptual Design of a Compact Fizeau Interferomet

er

Neng-hong Zhu, Xin-yang Chen

Shanghai Astronomical Observatory23/4/20

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Background & Goal• Dream: Optical long baseline interferometer based in space• Reality: Optical interferometry of China is just in inital stage

+ limited money• Option: Compact Fizeau Space Interferometer

short baseline direct instantaneous imaging small scale

• Step 1: gound prototype with diameter equivalent to 1m

Step 2: Fizeau space Interferometer with diameter equivalent to 2~4m

future: longer baseline & more elements...

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Array configurationGeometric Array

Modulation Transfer Function: MTF=|FT(PSF)|

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

1

2

3

4

5

6x 10

16

square d=0.4m L=0.3995m Deff=0.89398m

Y-3 d=0.4m L=0.39837m Deff=0.79998m

Y-4 d=0.4m L=0.65m Deff=1.0278m

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

1

2

3

4

5

6x 10

16

square d=0.4m L=0.3995m Deff=0.89398m

Y-3 d=0.4m L=0.39837m Deff=0.79998m

Y-4 d=0.4m L=0.65m Deff=1.0278m

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

1

2

3

4

5

6x 10

16

square d=0.4m L=0.3995m Deff=0.89398m

Y-3 d=0.4m L=0.39837m Deff=0.79998m

Y-4 d=0.4m L=0.65m Deff=1.0278m

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

1

2

3

4

5

6x 10

16

square d=0.4m L=0.3995m Deff=0.89398m

Y-3 d=0.4m L=0.39837m Deff=0.79998m

Y-4 d=0.4m L=0.65m Deff=1.0278m

α=0° α=10°

α=20° α=30°

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Beam combining errors (1/2)

• PSF vs. piston error

piston=-0.2λpiston=-0.4λ piston=0.2λ piston=0.4λ

MTF vs. piston

Strehl Ratio vs. piston

SR≥0.9 -----> piston P-V≤0.1λ

[Cao Fang, et al, 2008]

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Beam combining errors (2/2)

• PSF vs. tip/tilt error

X tip=0

X tip=0.2λ X tip=0.1λ X tip=0.3λ

Y tilt=0 Y tilt=0.2λ Y tilt=0.1λ Y tilt=0.3λ

MTF vs. tip/tilt

Strel Ratio vs. tip/tilt SR≥0.9 -----> tip/tilt P-V≤0.055λ≈0.

3"

[Cao Fang, et al, 2008]

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Spec. of the ground prototype

• Y-4 array -----> (1) high stability due to symmetric structure (2) optimal MTF (3) tubes modulization

• common mounting -----> without optical delay line for compensating outer OPD• C-shape board & triangle flatform -----> high stiffness & resonance freq. • wide FOV ~ ±2 '• Direct Drive -----> no backlash, high tracking accuracy ~ RMS:0.01"(Dec=45°)

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FEA of structure

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Optics design

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3

4

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7

8 9 10 11 12 13

14

15

16

17

18

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19 SIT-19

子孔径望远镜主镜

场镜

准直物镜组

朱能鸿

周丹 光学系统

旋转光阑

四棱锥组件

CCD出瞳检测 相机-2反射镜

综合孔径

中国科学院上海天文台朱能鸿

( )重量 公斤

第 张

图样标记 数量

共 张

文 件 号 签 字日期标记处所

:材料日期 批 准

审 核

部件设计

设 计 比例

干涉成像望远镜

18 SIT-18

17 SIT-17

16 SIT-16-00

Tip-Tilt -2镜

CCD干涉条纹检测 相机

分光立方棱镜

反射棱镜

分光平面镜

SIT-15

SIT-14

SIT-13

SIT-12

SIT-11

SIT-10

SIT-09-00

1514131211109 合成物镜组

Piston镜

Tip-Tilt -1镜

调焦物镜

-1反射镜

CCD干涉成像 相机

子孔径望远镜副镜

SIT-08

SIT-07

SIT-06

SIT-05-00

SIT-04

SIT-03

SIT-02

SIT-01

87654321序号 件号 名称 备注总重单重材料数量

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sub-telescope optics

folding & combiner optics confusion circle Φ≤ 0.7"Primary mirror

Outer diameter(mm)

420 Inner diameter(mm)

80

Thickness(mm) 60 Weight (Kg) 20

f/D ratio 2 Eccentricity 1.020466

Secondary mirror

Outer diameter(mm)

80 Curvature radii 336

Thickness(mm) 15 Weight (Kg) 0.15

Eccentricity 2.076363

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Challenge• How to measure and eliminate co-phasing errors b

etween sub-telescopes? pyramid wavefront sensor fringe tracking

How to improve image quality? interferometric image restoration method -> better MTF