CN114137721A - High-contrast imaging coronagraph micro-point density modulation system and working method - Google Patents
High-contrast imaging coronagraph micro-point density modulation system and working method Download PDFInfo
- Publication number
- CN114137721A CN114137721A CN202111204451.3A CN202111204451A CN114137721A CN 114137721 A CN114137721 A CN 114137721A CN 202111204451 A CN202111204451 A CN 202111204451A CN 114137721 A CN114137721 A CN 114137721A
- Authority
- CN
- China
- Prior art keywords
- micro
- modulation
- points
- coronagraph
- imaging
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000003384 imaging method Methods 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims abstract description 16
- 210000001747 pupil Anatomy 0.000 claims abstract description 38
- 238000002834 transmittance Methods 0.000 claims abstract description 25
- 238000013461 design Methods 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 5
- 230000002457 bidirectional effect Effects 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 2
- 238000011017 operating method Methods 0.000 claims 2
- 230000005540 biological transmission Effects 0.000 abstract description 6
- 230000000694 effects Effects 0.000 abstract description 2
- 238000011160 research Methods 0.000 description 8
- 238000001514 detection method Methods 0.000 description 7
- 238000011161 development Methods 0.000 description 7
- 238000010586 diagram Methods 0.000 description 5
- VAYOSLLFUXYJDT-RDTXWAMCSA-N Lysergic acid diethylamide Chemical compound C1=CC(C=2[C@H](N(C)C[C@@H](C=2)C(=O)N(CC)CC)C2)=C3C2=CNC3=C1 VAYOSLLFUXYJDT-RDTXWAMCSA-N 0.000 description 4
- 238000012545 processing Methods 0.000 description 4
- 230000003595 spectral effect Effects 0.000 description 3
- 241000282414 Homo sapiens Species 0.000 description 2
- 208000000418 Premature Cardiac Complexes Diseases 0.000 description 2
- 235000019892 Stellar Nutrition 0.000 description 2
- 238000005457 optimization Methods 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 241001498882 Calliphlox Species 0.000 description 1
- 241001183967 Isodon Species 0.000 description 1
- 230000003044 adaptive effect Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000001266 bandaging Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000007888 film coating Substances 0.000 description 1
- 238000009501 film coating Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005192 partition Methods 0.000 description 1
- 238000001259 photo etching Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
- G02B27/0012—Optical design, e.g. procedures, algorithms, optimisation routines
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Studio Devices (AREA)
Abstract
The invention discloses a high-contrast imaging coronagraph micro-point density modulation system, which relates to the technical field of coronagraphs and comprises a telescope entrance end, a reflector, a collimator, an aperture diaphragm, a pupil modulator, an imaging mirror and a detector, wherein the reflector is provided with two pieces which are respectively positioned between the telescope entrance end, the collimator, the pupil modulator and the imaging mirror, the pupil modulator comprises a plurality of modulation bands, each modulation band is provided with a plurality of bright micro-points and dark micro-points, the number range of the adjustment bands of the pupil modulator is 10-200, and the invention also provides a working method of the high-contrast imaging coronagraph micro-point density modulation system. The high-contrast imaging coronagraph micro-point density modulation system achieves the purpose of transmittance change modulation by changing the spatial density distribution of light and dark micro-points on a modulation band, can achieve the same modulation effect on all working wavelengths, and can thoroughly solve the technical problem that the light transmission efficiency of the traditional coronagraph is limited due to the fact that an observation wave band is too narrow.
Description
Technical Field
The invention relates to the technical field of coronagraphs, in particular to a high-contrast imaging coronagraph micro-point density modulation system and a working method.
Background
Extravehicular planets refer to planets outside the solar system, i.e., planets around other stars or planets flying independently outside the solar system. The extraterrestrial planet detection is closely related to the search of extraterrestrial civilization, so that the understanding of human beings on the existing life can be broken through, and the living space of human beings can be expanded finally. To date, 4700 multiple outer planets have been detected, mostly indirectly by the method of Rabdosia or Doppler. The direct imaging technology can really see the extrasystal planets and is the key for confirming extrasystal life characteristic signals. The coronagraph is an important instrument for high-contrast direct imaging detection of extraterrestrial planets, and can effectively inhibit strong light of fixed stars, so that planets submerged in strong background light of the fixed stars can be directly detected.
At present, limited by the ground atmospheric environment and the observation wave band and the detection capability of a new generation of super adaptive optical technology, the ground-based planetary imaging coronagraph can only carry out planetary imaging detection in an infrared wave band, and finds that the targets are mostly young planets in formation, and the mass range is from several to more than ten of the masses of the wood stars. The search for cold planets around the sun-like fixed star, especially the earth-like planets in the livable zone, is a breakthrough for detecting and confirming the existence of the life planets in the future, which needs to break through the limitations of the existing ground observation wave band and imaging contrast and needs to develop the ultrahigh contrast imaging technology of the space coronarism instrument.
The space coronagraph system carries out high-contrast imaging on extrasystole planets, and whether targets are found by detection or subsequent atmospheric spectrum research is carried out, enough image signal-to-noise ratio of the planets needs to be acquired. Accordingly, a coronagraph is required to have a high system luminous efficiency. The bandwidth of the observation wave band corresponding to the working wavelength is an important technical index for restricting the improvement of the system efficiency of the coronagraph.
The traditional coronagraph system is limited by the modulation technical mode, and can only realize high-contrast imaging in a narrow observation wave band, for example, the working wavelength bandwidth is only 3-5%. The light transmission efficiency of the existing system is limited, the signal-to-noise ratio of the planet image acquired within a certain observation time is limited, and due to incomplete coverage of the characteristic spectral line, the subsequent spectral detailed depicting research on the planet atmosphere is not facilitated.
The research is supported by the scientific research expenditure of the special item of the space patrol telescope of the manned space engineering carried in China, the subject numbers of CMS-CSST-2021-A11 and CMS-CSST-2021-B04, and the national science foundation astronomical joint key supporting project of ' extrasolar planet high contrast imaging key technology research for large-caliber spliced mirror telescope ' (U2031210) and ' extrasolar planet high contrast imaging detector development around dark and weak stars ' of the national major scientific research instrument development project ' (11827804);
disclosure of Invention
The invention aims to provide a high-contrast imaging coronagraph micro-point density modulation system and a working method, and aims to solve the problems that the traditional coronagraph system is limited by a modulation technical mode in the background technology, high-contrast imaging can be realized only in a narrow observation wave band, the light transmission efficiency of the existing system is limited, and the subsequent spectral detailed description research on planet atmosphere is not facilitated.
In order to achieve the purpose, the invention provides the following technical scheme: a working method of a high-contrast imaging coronagraph micro-point density modulation system comprises the following steps:
s1: establishing a coronagraph system, and preliminarily determining the effective light-passing aperture, the band number of the pupil modulator and the modulation function trend of the system according to the size of an optical element of the system, the working area of the pupil modulator and system design indexes;
s2: calculating the transmittance value of each modulation band according to the imaging contrast index requirement of the coronagraph;
s3: designing a density layout scheme of light and dark micro-points according to the transmittance value corresponding to each transmittance band, wherein each modulation band is provided with M light micro-points, the transmittance of the light micro-points corresponds to 1, N dark micro-points, the transmittance of the dark micro-points corresponds to 0, and the transmittance of the modulation band corresponds to N/M;
s4: calculating the imaging contrast of the design micro-point variable density layout scheme;
s5: optimizing the spatial arrangement of light and shade micro-points, calculating the imaging contrast in a specific working area, and judging whether the contrast is 10-6-10-8Within the range, if the judgment result is notAnd step S5 is repeated, and if the judgment result is yes, the process is ended.
Preferably, the density layout scheme is a mode of randomly laying out micro-points in each modulation zone inner subarea and molecular area or a mode of laying out micro-points along a specific direction and pattern.
Further preferably, the pupil modulation scheme in the pupil modulator is unidirectional or bidirectional modulation.
The invention also provides a high-contrast imaging coronagraph micro-point density modulation system which comprises a telescope entrance end, a reflector, a collimator, an aperture diaphragm, a pupil modulator, an imaging mirror and a detector, wherein the reflector is provided with two pieces which are respectively positioned among the telescope entrance end, the collimator, the pupil modulator and the imaging mirror, the pupil modulator comprises a plurality of modulation bands, and each modulation band is provided with a plurality of bright micro-points and dark micro-points.
Preferably, the adjustment band number of the pupil modulator is in the range of 10-200.
Compared with the prior art, the invention has the beneficial effects that: the modulation of light energy is realized by changing the spatial density distribution of a darkening strip, the same modulation effect can be realized for all working wavelengths, the technical problem that the light transmission efficiency of the traditional coronagraph is limited due to the narrow observation wave band can be thoroughly solved, and the method is as follows:
1. the modulation scheme of a limited number of modulation bands is adopted, the modulation band range is 10-200, the development difficulty of a system is effectively reduced, the processing precision of a modulator is ensured, the development period and the cost are reduced, and ultrahigh contrast imaging becomes possible;
2. each modulation band realizes the requirement of the integral transmittance value on the corresponding band by changing the density distribution of 0 or 1 light and dark micro-points, and the spatial arrangement mode of the light and dark micro-points can adopt a mode of randomly arranging the micro-points in a subregion and a molecular region in each modulation band or a mode of arranging the micro-points along a specific direction or pattern based on the transmittance optimized by pupil modulation, thereby improving the imaging contrast;
3. based on the transmittance optimized by pupil modulation, the spatial layout of bright and dark micro-points is optimized by reverse iteration, the optimal micro-point variable density spatial distribution is obtained by the closed loop of the system and the combination of the actual processing technology and the precision capability, and the high-precision development of the modulator is ensured;
4. the system can flexibly adopt a one-way or two-way pupil modulation scheme, not only can ensure that the system obtains enough light transmission efficiency, but also can obtain ultrahigh contrast imaging performance in a larger working area to the maximum extent, and promotes direct imaging detection and atmospheric spectrum research of the externally cooling planets.
Drawings
FIG. 1 is a schematic diagram of the overall layout structure of a coronagraph system according to the present invention;
FIG. 2 is a schematic diagram of the modulation configuration in the horizontal and vertical directions according to the scheme of randomly distributing micro-dots in the inner partition of the modulation band;
FIG. 3 is a schematic diagram of the configuration of the present invention for transverse and vertical modulation according to the layout of micro-dots in a specific direction in the modulation zone;
FIG. 4 is a schematic diagram of the bi-directional superposition modulation configuration of FIGS. 2 and 3 in accordance with the present invention;
FIG. 5 is a schematic diagram of the design steps and optimization process of the present invention.
In the figure: 1. simulating a light source; 2. a mirror; 3. a collimating mirror; 4. an aperture diaphragm; 5. a pupil modulator; 6. an imaging mirror; 7, a detector.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-5, the present invention provides a technical solution: a working method of a high-contrast imaging coronagraph micro-point density modulation system comprises the following steps:
s1: establishing a coronagraph system, and preliminarily determining the effective clear aperture, the pupil modulator band number and the modulation function trend of the system according to the size of an optical element of the system, the pupil modulator working area and system design indexes, wherein the effective clear aperture of the system is related to the size of the optical element of the system, if the clear aperture is too large, the volume of the system is too large, and on the other hand, if the effective clear aperture is too small, the bandwidth of each band of a pupil modulation sheet is reduced, which increases the difficulty of film coating, so that the effective clear aperture range of the system is within the range of 10 mm-200 mm under the common condition; the band number of the pupil modulator is in direct proportion to the size of a working area, so the design is usually carried out according to the technical index of a coronagraph, and the band number of the pupil modulator is about 10-200 bands under the normal condition;
s2: calculating the transmittance value of each modulation band according to the imaging contrast index requirement of the coronagraph and the requirement of a working area;
s3: designing a density layout scheme of light and dark micro-points according to the transmittance value corresponding to each transmittance band, wherein each modulation band is provided with M light micro-points, the transmittance of the light micro-points corresponds to 1, N dark micro-points, the transmittance of the dark micro-points corresponds to 0, and the transmittance of the modulation band corresponds to N/M;
s4: calculating the above design micro-point variable density layout scheme (transmittance T) and substituting into a formula,
calculating to obtain a system focal point spread function image, and then calculating the imaging contrast of the system;
s5: optimizing the spatial arrangement of light and shade micro-points, calculating the imaging contrast in a specific working area, and judging whether the contrast is 10-6-10-8Within the range, if the judgment result is not yes, the step S5 is repeated, and if the judgment result is yes, the process is ended.
As shown in fig. 2 and fig. 3, the density layout scheme is preferably a way of randomly laying out microdots in a subarea and a molecular area in each modulation band or a way of laying out microdots along a specific direction and pattern, so that difficulty in developing a system is reduced, processing accuracy of a modulator is guaranteed, development period and cost are reduced, and imaging contrast is improved.
As shown in fig. 4, preferably, the pupil modulation scheme in the pupil modulator is unidirectional or bidirectional modulation, and the unidirectional or bidirectional pupil modulation scheme is flexibly adopted, so that not only can the system be ensured to obtain sufficient light transmission efficiency, but also ultrahigh contrast imaging performance can be obtained in a larger working area to the maximum extent.
According to the method, the inter-band transmittance is designed, then the spatial density arrangement of bright and dark micro-points is optimized according to the transmittance, the optimal spatial distribution is obtained by combining the actual processing technology and the precision capability, the high-precision development of the modulator is ensured, the closed-loop optimization efficiency of the system can be effectively improved by the design, and the final imaging contrast performance of the system is ensured.
The invention also provides a high-contrast imaging coronagraph micro-point density modulation system which comprises a telescope entrance end 1, a reflector 2, a collimator 3, an aperture diaphragm 4, a pupil modulator 5, an imaging mirror 6 and a detector 7, wherein the reflector 2 is provided with two pieces which are respectively positioned among the telescope entrance end 1, the collimator 3, the pupil modulator 5 and the imaging mirror 6, the pupil modulator 5 comprises a plurality of modulation bands, the number range of the adjustment bands of the pupil modulator is 10-200, each modulation band is provided with a plurality of light micro-points and dark micro-points, and the light and dark micro-points on the modulation bands can be processed and manufactured by a high-precision photoetching technology.
When the telescope is used, a simulated point light source is placed at the incident end 1 (focus) of the telescope, and is converted to the collimating mirror 3 through the reflecting mirror 2 to expand a point source target into parallel light so as to simulate stellar light at infinity; the aperture diaphragm 4 is used for blocking out unwanted stray light from the system, and the annulus pupil modulator 5 modulates the star light energy, and finally the star light energy is turned to the paraboloid imaging mirror 6 through the reflecting mirror 2 to be imaged on the focal plane detector 7 of the coronarism system.
The energy of the stellar light at the pupil is modulated and redistributed, so that the energy distribution of a point spread function image of a 1-focal-plane system at the entrance end of the telescope can be changed, high-contrast imaging is obtained in a specific working area, and direct imaging detection of the extrasystole planets is realized.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (5)
1. A working method of a high-contrast imaging coronagraph micro-point density modulation system is characterized by comprising the following steps: the method comprises the following steps:
s1: establishing a coronagraph system, and preliminarily determining the effective light-passing aperture, the band number of the pupil modulator and the modulation function trend of the system according to the size of an optical element of the system, the working area of the pupil modulator and system design indexes;
s2: calculating the transmittance value of each modulation band according to the imaging contrast index requirement of the coronagraph;
s3: designing a density layout scheme of light and dark micro-points according to the transmittance value corresponding to each transmittance band, wherein each modulation band is provided with M light micro-points, the transmittance of the light micro-points corresponds to 1, N dark micro-points, the transmittance of the dark micro-points corresponds to 0, and the transmittance of the modulation band corresponds to N/M;
s4: calculating the imaging contrast of the design micro-point variable density layout scheme;
s5: optimizing the spatial arrangement of light and shade micro-points, calculating the imaging contrast in a specific working area, and judging whether the contrast is 10-6-10-8Within the range, if the judgment result is not yes, the step S5 is repeated, and if the judgment result is yes, the process is ended.
2. The operating method of the high-contrast imaging coronagraph micro-point density modulation system according to claim 1, wherein: the density layout scheme is a mode of randomly laying out micro-points in a subarea and a molecular area in each modulation band or a mode of laying out the micro-points along a specific direction and pattern.
3. The operating method of the high-contrast imaging coronagraph micro-point density modulation system according to claim 1 or 2, characterized in that: the pupil modulation scheme in the pupil modulator is either unidirectional or bidirectional modulation.
4. The utility model provides a high contrast formation of image coronagraph microspot density modulation system, includes telescope incident end, speculum, collimating mirror, aperture diaphragm, pupil modulator, imaging mirror and detector, and the speculum is equipped with two, is located respectively between telescope incident end, collimating mirror and pupil modulator, the imaging mirror, its characterized in that: the pupil modulator comprises a plurality of modulation bands, and each modulation band is provided with a plurality of light micro-points and dark micro-points.
5. The system of claim 4, wherein the system comprises: the adjustment band number of the pupil modulator ranges from 10 to 200.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111204451.3A CN114137721A (en) | 2021-10-15 | 2021-10-15 | High-contrast imaging coronagraph micro-point density modulation system and working method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111204451.3A CN114137721A (en) | 2021-10-15 | 2021-10-15 | High-contrast imaging coronagraph micro-point density modulation system and working method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN114137721A true CN114137721A (en) | 2022-03-04 |
Family
ID=80394183
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202111204451.3A Pending CN114137721A (en) | 2021-10-15 | 2021-10-15 | High-contrast imaging coronagraph micro-point density modulation system and working method |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114137721A (en) |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103399401A (en) * | 2013-07-15 | 2013-11-20 | 北京理工大学 | Wavefront error correction system and method for inhibiting speckle noises of coronagraph system |
| CN113176079A (en) * | 2021-05-17 | 2021-07-27 | 中国科学院国家天文台南京天文光学技术研究所 | Ultrahigh-precision wavefront detection and calibration method for high-contrast imaging coronagraph |
| CN115265789A (en) * | 2022-07-04 | 2022-11-01 | 临沂大学 | High-contrast polarization imaging system for direct imaging of extrasystematic planets |
-
2021
- 2021-10-15 CN CN202111204451.3A patent/CN114137721A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103399401A (en) * | 2013-07-15 | 2013-11-20 | 北京理工大学 | Wavefront error correction system and method for inhibiting speckle noises of coronagraph system |
| CN113176079A (en) * | 2021-05-17 | 2021-07-27 | 中国科学院国家天文台南京天文光学技术研究所 | Ultrahigh-precision wavefront detection and calibration method for high-contrast imaging coronagraph |
| CN115265789A (en) * | 2022-07-04 | 2022-11-01 | 临沂大学 | High-contrast polarization imaging system for direct imaging of extrasystematic planets |
Non-Patent Citations (2)
| Title |
|---|
| DEQING REN, ET AL.: "A differential-imaging polarimeter for high-contrast exoplanet imaging" * |
| 邓可燃 等: "Construction of EXIST（Exoplant Imaging System Testbed） toword future space coronagraphs" * |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Delrez et al. | SPECULOOS: a network of robotic telescopes to hunt for terrestrial planets around the nearest ultracool dwarfs | |
| Kawanomoto et al. | Hyper Suprime-Cam: Filters | |
| Little | A diffraction theory of the scintillation of stars on optical and radio wave-lengths | |
| CN106289524A (en) | Spectrum imaging system based on free form surface | |
| CN116243470A (en) | Focusing ultra-long wave infrared optical imaging system used under low temperature condition | |
| CN101881844B (en) | Girdle photon sieve and manufacturing method thereof | |
| CN101398493A (en) | Amplitude type zone plate photonsieve | |
| Baez et al. | Panchromatic HST/WFC3 Imaging Studies of Young, Rapidly Evolving Planetary Nebulae. II. NGC 7027 | |
| CN114137721A (en) | High-contrast imaging coronagraph micro-point density modulation system and working method | |
| US3200253A (en) | System for obtaining parallel radiant energy rays of uniform illumination and uniform energy distribution | |
| CN105092031B (en) | A kind of infrared high spectrum imaging system with cold stop | |
| CN113639863B (en) | Space broadband ultra-high contrast imaging method and star crown instrument system | |
| CN113325483B (en) | Space-based multi-mode extrasystematic and extraterrestrial planet comprehensive detection method and system | |
| US20090302240A1 (en) | Solar photon filter | |
| CN107065174B (en) | A kind of big visual field thin film diffraction achromatic optical system and infrared light bearing calibration | |
| CN113639864B (en) | Space full-area ultrahigh contrast imaging method and star crown instrument system | |
| Benvenuti et al. | Optical investigation of the spiral galaxy NGC 660 | |
| CN114137720A (en) | Pupil modulation coronagraph system for high-contrast imaging and working method | |
| CN108168702B (en) | Full-aperture back scattered light measurement system based on scattering plate scattering sampling | |
| Rabl et al. | Iterative algorithm for reflector design for nonisotropic sources | |
| CN115826075B (en) | Device and method for identifying strong and weak daytime light background targets | |
| CN114594587B (en) | Optical imaging system for ultraviolet night-time | |
| Snow et al. | Experimental measurements of light emissions from Ontario greenhouses using supplemental lighting at night | |
| CN221037678U (en) | Imaging spectrometer optical system based on dichroic prism | |
| Perryman et al. | Report by the ESA-ESO Working Group on Extra-Solar Planets |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| CB02 | Change of applicant information |
Country or region after: China Address after: No. 188, Bancang street, Xuanwu District, Nanjing, Jiangsu Province, 210042 Applicant after: Nanjing Institute of Astronomical Optics, Chinese Academy of Sciences Address before: No. 188, Bancang street, Xuanwu District, Nanjing, Jiangsu Province, 210042 Applicant before: NANJING INSTITUTE OF ASTRONOMICAL OPTICS & TECHNOLOGY, NATIONAL ASTRONOMICAL OBSERVATORIES, CAS Country or region before: China |