Acta Optica Sinica, Volume. 43, Issue 8, 0822018(2023)
Design of Geostationary Full-Spectrum Wide-Swath High-Fidelity Imaging Spectrometer and Development of Its Spectrometers
Figures & Tables(27)
Fig. 1. Working principle diagram of GeoFWHIS. (a) Layout diagram; (b) pointing to different coverages by turning the platform
Fig. 2. Afocal three-mirror system. (a) Coaxial three-mirror; (b) off-axis three-mirror; (c) zigzag-axis three-mirror
Fig. 3. Off-axis three-mirror imaging systems. (a) Two-mirror system; (b) three-mirror system with intermediate image; (c) three-mirror system without intermediate image
Fig. 4. Optical path of fore-optics system. (a) 3D model of fore-optics system; (b) optical path with scanning mirror at edge position of -2.56°; (c) optical path with scanning mirror at edge position of +2.56°
Fig. 5. MTF curves and spot diagrams of fore-optics system in B2 band. (a)-(c) MTF curves with scanning angle of -2.56°, 0°, and +2.56°; (d)-(f) sport diagrams with scanning angle of -2.56°, 0°, and +2.56°
Fig. 8. Optical path of spectrometers in GeoFWHIS. (a) B1 band; (b) B2 band; (c) B3 band; (d) B4 band; (e) B5 band
Fig. 9. SRF of optical splitting systems for each band. (a) B1 band; (b) B2 band; (c) B3 band; (d) B4 band; (e) B5 band
Fig. 11. SNR curves for B2 band in cloudless environment when observation zenith angle is 35° and integration time is 80 ms
Fig. 12. Silicon long slits. (a) Slit for B1 and B2 bands with length of 61.44 mm and width of 15 μm; (b) slit for B3 and B4 bands with length of 49.16 mm and width of 24 μm; (c) slit for B5 band with length of 24.58 mm and width of 24 μm
Fig. 13. Micrograph of slit for B2. (a) 10× micrograph; (a) test result of slit width
Fig. 14. Convex blazed gratings and their groove shapes, the lower right corner shows AFM test results of groove shapes. (a) B1 band, groove density is 312.1 lp/mm and blazed angle is 3.8°; (b) B2 band, groove density is 210.1 lp/mm and blazed angle is 4.75°; (c) B3 band, groove density is 68.5 lp/mm and blazed angle is 3.1°; (d) B4 band, groove density is 19.1 lp/mm and blazed angle is 2.8°; (e) B5 band, groove density is 8.8 lp/mm and blazed angle is 2.8°
Fig. 15. Diffraction efficiency curves of gratings at B1-B5 bands. (a) B1 band; (b) B2 band; (c) B3 band; (d) B4 band; (e) B5 band
Fig. 16. Alignment of the spectrometer by utilizing a point source microscope. (a) Self-developed point source microscope; (b) alignment of two separated meniscus in B3 spectrometer with point source microscope; (c) star images of two spherical surfaces in field of view of point source microscope
Fig. 17. Full-spectrum spectrometer prototypes. (a) B1 band; (b) B2 band; (c) B3 band; (d) B4 band; (e) B5 band
Fig. 18. Test device and test results of B2 spectrometer. (a) Test device of spectral property; (b) spectral lines; (c) SRF of 546.1 nm spectral line; (d) scatter diagram of 546.1 nm spectral line and its fitting curve
Fig. 19. Test device and spectral lines of B5 spectrometer. (a) Test device; (b) spectral lines
Table 1. Specifications and system parameters of GeoFWHIS
View tableTable 1. Specifications and system parameters of GeoFWHIS
Specification and parameter Value Orbital altitude Geostationary orbit（~36000 km） Swath width /（km×km） 400×400 Field of view /［（°）×（°）］ 0.64×0.64 Entrance pupil diameter /m 3.2
Table 2. System parameters of GeoFWHIS at full-spectrum
View tableTable 2. System parameters of GeoFWHIS at full-spectrum
Band B1 B2 B3 B4 B5 Wavelength range /μm 0.3-0.56 0.55-1.01 1-2.5 3-5 8-12.5 Spatial resolution /m 25 25 50 50 100 Spectral resolution /nm 4 5 10 50 200 MTF 0.17 0.17 0.17 0.12 0.12 SNR 250 250 150 — — NETD /K — — — 0.3 0.3 Focal length /m 21.6 21.6 17.28 17.28 8.64 F number 6.75 6.75 5.4 5.4 2.7 Detector resolution 4096×2048 4096×2048 2048×256 2048×256 1024×256 Pixel size /μm 15×15 15×15 24×32 24×32 24×32 Total length of slit /mm 241.3 241.3 193 193 96.5 Number of splicing spectrometers 4 4 4 4 4 Single slit length /mm 61.44 61.44 49.152 49.152 24.576
Table 3. Specifications of three objectives
View tableTable 3. Specifications of three objectives
Specification Objective Ⅰ Objective Ⅱ Objective Ⅲ Wavelength range /μm 0.3-1.01 1-5 8-12.5 Entrance pupil diameter /mm 200 200 200 Field of fiew /［（°）×（°）］ 10.24×0.22 10.24×0.26 10.24×0.53 Focal length /mm 1350 1080 540 F number 6.75 5.4 2.7
Table 4. Comparison of advantages and disadvantages for different spectrometers
View tableTable 4. Comparison of advantages and disadvantages for different spectrometers
Spectrometer type Characteristic Advantage Disadvantage Offner ·Convex grating;
·Concentric structure
·Long working distance;
·No smile and keystone
·Large volume with a long slit;
·Residual astigmatism
Wynne-Offner ·A meniscus is added near the grating of Offner type ·Advantages of Offner type;
·Anastigmatism;
·Compact
·Additional polarization;
·Hard to manufacture grating on meniscus
Freeform Offner ·Three freeform elements ·Advantages of Offner type;
·Compact
·Extremely difficulty;
·High cost
Immersed Offner ·Light travels in dielectric ·Advantages of Offner type;
·Ultra-compact
·High cost;
·High risk
Dyson ·Concave grating;
·Concentric structure
·Large relative aperture;
·No smile and keystone
·Large volume with a long slit;
·Short working distance
Wynne-Dyson ·A meniscus is added behind the hemispherical lens of Dyson type ·Advantages of Dyson type;
·Ultra-compact
·Short working distance Advanced
Dyson
·Several meniscus lenses added into the classic Dyson type ·Advantages of Dyson type;
·Relatively long working distance
·Large volume with a long slit R-T ·Double pass structure;
·Plane grating;
·Littrow mounting
·Compact;
·Small distortion
·High cost;
·Tight tolerance;
·Small space between slit and image
CCVIS ·Catadioptric structure;
·Immersed grating
·Long working distance;
·Compact
·Residual keystone;
·Thermal sensitive
Table 5. System parameters and performance of spectrometers
View tableTable 5. System parameters and performance of spectrometers
Band B1 B2 B3 B4 B5 Package size /（mm×mm×mm） 140×110×100 170×111×106 160×132×89 168×165×88 90×92×49 Smile /pixel 0.06% 0.11% 0.26% 0.31% 0.95% Keystone /pixel 0.33% 0.47% 0.79% 0.42% 1.00% MTF 0.86 0.77 0.72 0.41 0.28 Grating density /（lp·mm-1） 310 210 68 19.1 8.8 Blazed angle of grating /（°） 3.7 4.6 3.1 2.6 2.8
Table 6. MTF of GeoFWHIS at Nyquist frequency
View tableTable 6. MTF of GeoFWHIS at Nyquist frequency
Band Serial number Scanning angle of -2.56° Scanning angle of 0° Scanning angle of +2.56° B1 Wavelength /μm 0.30 0.43 0.56 0.30 0.43 0.56 0.30 0.43 0.56 Diffraction limit 0.88 0.84 0.80 0.88 0.84 0.80 0.88 0.84 0.80 Spectrometer 1 0.80 0.76 0.75 0.80 0.79 0.77 0.60 0.59 0.57 Spectrometer 2 0.82 0.79 0.76 0.82 0.80 0.78 0.77 0.72 0.66 Spectrometer 3 0.81 0.79 0.77 0.85 0.79 0.78 0.75 0.71 0.63 Spectrometer 4 0.73 0.69 0.67 0.78 0.74 0.72 0.61 0.58 0.53 B2 Wavelength /μm 0.55 0.78 1.01 0.55 0.78 1.01 0.55 0.78 1.01 Diffraction limit 0.78 0.72 0.66 0.78 0.72 0.66 0.78 0.72 0.66 Spectrometer 1 0.65 0.62 0.57 0.71 0.64 0.59 0.60 0.58 0.53 Spectrometer 2 0.66 0.65 0.58 0.74 0.70 0.62 0.65 0.62 0.56 Spectrometer 3 0.69 0.67 0.58 0.73 0.70 0.63 0.64 0.59 0.53 Spectrometer 4 0.65 0.60 0.56 0.72 0.69 0.62 0.60 0.55 0.52 B3 Wavelength /μm 1.00 1.75 2.50 1.00 1.75 2.50 1.00 1.75 2.50 Diffraction limit 0.84 0.74 0.63 0.84 0.74 0.63 0.84 0.74 0.63 Spectrometer 1 0.69 0.63 0.55 0.72 0.60 0.54 0.63 0.55 0.40 Spectrometer 2 0.79 0.70 0.62 0.81 0.70 0.65 0.69 0.62 0.51 Spectrometer 3 0.77 0.70 0.61 0.80 0.71 0.65 0.77 0.69 0.55 Spectrometer 4 0.78 0.71 0.61 0.79 0.68 0.63 0.78 0.66 0.54 B4 Wavelength /μm 3 4 5 3 4 5 3 4 5 Diffraction limit 0.52 0.47 0.42 0.52 0.47 0.42 0.52 0.47 0.42 Spectrometer 1 0.42 0.38 0.35 0.42 0.39 0.36 0.38 0.33 0.31 Spectrometer 2 0.49 0.45 0.40 0.50 0.46 0.42 0.45 0.45 0.39 Spectrometer 3 0.47 0.39 0.38 0.50 0.44 0.40 0.43 0.42 0.37 Spectrometer 4 0.46 0.40 0.32 0.47 0.39 0.34 0.36 0.32 0.29 B5 Wavelength /μm 8.0 10.3 12.5 8.0 10.3 12.5 8.0 10.3 12.5 Diffraction limit 0.35 0.31 0.27 0.35 0.31 0.27 0.35 0.31 0.27 Spectrometer 1 0.28 0.25 0.22 0.31 0.26 0.25 0.29 0.25 0.23 Spectrometer 2 0.31 0.27 0.23 0.32 0.27 0.24 0.31 0.27 0.24 Spectrometer 3 0.30 0.26 0.23 0.31 0.27 0.26 0.30 0.26 0.22 Spectrometer 4 0.29 0.25 0.24 0.30 0.26 0.23 0.30 0.25 0.22
Table 7. FWHM (spectral resolution) of B2 spectrometer
View tableTable 7. FWHM (spectral resolution) of B2 spectrometer
Wavelength /nm FWHM /nm -1 field -0.5 field 0 field +0.5 field +1 field Average 546.1 5.02 5.01 4.99 4.99 5.01 5.01 643.8 5.02 5.02 5.02 5.00 5.01 5.02 959.8 5.02 5.00 5.02 5.02 5.02 5.02 1017 5.02 5.02 5.01 5.01 5.02 5.02
Table 8. FWHM (spectral resolution) of B5 spectrometer
View tableTable 8. FWHM (spectral resolution) of B5 spectrometer
Wavelength /nm FWHM /nm -1 field 0 field +1 field Average 8224 201.3 201.0 200.9 201.1 8834 202.4 202.1 201.9 202.1 9350 205.9 204.9 204.2 205.0
Tools
Get Citation
Copy Citation Text
Jiacheng Zhu, Zhicheng Zhao, Quan Liu, Xinhua Chen, Huan Li, Shaofan Tang, Weimin Shen. Design of Geostationary Full-Spectrum Wide-Swath High-Fidelity Imaging Spectrometer and Development of Its Spectrometers[J]. Acta Optica Sinica, 2023, 43(8): 0822018
Paper Information
Category: Optical Design and Fabrication
Received: Oct. 26, 2022
Accepted: Nov. 25, 2022
Published Online: Apr. 6, 2023
The Author Email: Liu Quan (liuquan@suda.edu.cn), Shen Weimin (swm@suda.edu.cn)
© Copyright 2018-2021 | Chinese Laser Press.
All Rights Reserved 沪ICP备15018463号-20