• Journal of Astronomy and Space Sciences
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• v.36 no.3
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• pp.169-180
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• 2019

In this study, a batch least square estimator that utilizes optical observation data is developed and utilized to determine geostationary orbits (GEO). Through numerical simulations, the effects of error sources, such as clock errors, measurement noise, and the a priori state error, are analyzed. The actual optical tracking data of a GEO satellite, the Communication, Ocean and Meteorological Satellite (COMS), provided by the optical wide-field patrol network (OWL-Net) is used with the developed batch filter for orbit determination. The accuracy of the determined orbit is evaluated by comparison with two-line elements (TLE) and confirmed as proper for the continuous monitoring of GEO objects. Also, the measurement residuals are converged to several arcseconds, corresponding to the OWL-Net performance. Based on these analyses, it is verified that the independent operation of electro-optic space surveillance systems is possible, and the ephemerides of space objects can be obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.805-808
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• 2005

This paper is a study on an optical bench satisfying stiffness and thermal pointing error requirements for LEO earth observation satellite. According to shape and stiffness requirements, optical bench type 1 is designed. Because type 1 does not satisfy the thermal pointing error requirement, an optical bench type 2 is suggested. Although the type 2 has better results than type 1, it still does not meet the thermal pointing error requirement. Using the results of optical bench type 1&2, the optical bench type 3 is finally designed, which satisfies both the stiffness and thermal pointing error requirements.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.319-332
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• 2011

The objectives of this study are to analyze the satellite visibility at the randomly established ground sites, to determine the five optimal ground sites to perform the optical surveillance and tracking of domestic satellites, and to verify the acquisition of the optical observation time sufficient to maintain the precise ephemeris at optimal ground sites that have been already determined. In order to accomplish these objectives, we analyzed the visibility for sun-synchronous orbit satellites, low earth orbit satellites, middle earth orbit satellites and domestic satellites as well as the continuous visibility along with the fictitious satellite ground track, and calculate the effective visibility. For the analysis, we carried out a series of repetitive process using the satellite tool kit simulation software developed by Analytical Graphics Incorporated. The lighting states of the penumbra and direct sun were set as the key constraints of the optical observation. The minimum of the observation satellite elevation angle was set to be 20 degree, whereas the maximum of the sun elevation angle was set to be -10 degree which is within the range of the nautical twilight. To select the candidates for the optimal optical observation, the entire globe was divided into 84 sectors in a constant interval, the visibility characteristics of the individual sectors were analyzed, and 17 ground sites were arbitrarily selected and analyzed further. Finally, five optimal ground sites (Khurel Togoot Observatory, Assy-Turgen Observatory, Tubitak National Observatory, Bisdee Tier Optical Astronomy Observatory, and South Africa Astronomical Observatory) were determined. The total observation period was decided as one year. To examine the seasonal variation, the simulation was performed for the period of three days or less with respect to spring, summer, fall and winter. In conclusion, we decided the optimal ground sites to perform the optical surveillance and tracking of domestic satellites and verified that optical observation time sufficient to maintain the precise ephemeris could be acquired at the determined observatories.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.207-210
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• 2005

In this paper, technical issues for an optical bench of high precision LEO Earth observation satellite are described. The optical bench should be stable for thermal and dynamic environment. In this point of view, an intermediate type of optical bench is developed. Thermal deformation analysis and modal analysis are performed for two types of FE model. Modal test are performed to verify the analysis results. The test results fit well the analysis results.

• Proceedings of the KSRS Conference
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• 2007.10a
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• pp.349-352
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• 2007

The Fourth Assessment Report of IPCC predicted that global warming is already happening and it should be caused from the increase of greenhouse gases by the extension of human activities. These global changes will give a serious influence for human society. Global environment can be monitored by the earth observation using satellite. For the observation of global climate change and resolving the global warming process, satellite should be useful equipment and its detecting data contribute to social benefits effectively. JAXA (former NASDA) has made a new plan of the Global Change Observation Mission (GCOM) for monitoring of global environmental change. SGLI (Second Generation GLI) onboard GCOM-C (Climate) satellite, which is one of this mission, provides an optical sensor from Near-DV to TIR. Characteristic specifications of SGLI are as follows; 1) 250 m resolutions over land and area along the shore, 2) Three directional polarization observation (red and NIR), and 3) 500 m resolutions temperature over land and area along shore. These characteristics are useful in many fields of social benefits. For example, multi-angular observation and 250 m high frequency observation give new knowledge in monitoring of land vegetation. It is expected that land products with land aerosol information by polarization observation are improved remarkably. We are studying these possibilities by ground data and satellite data.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.201-207
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• 2015

An algorithm to automatically extract coordinate and time information from optical observation data of geostationary orbit satellites (GEO satellites) or geosynchronous orbit satellites (GOS satellites) is developed. The optical wide-field patrol system is capable of automatic observation using a pre-arranged schedule. Therefore, if this type of automatic analysis algorithm is available, daily unmanned monitoring of GEO satellites can be possible. For data acquisition for development, the COMS1 satellite was observed with 1-s exposure time and 1-m interval. The images were grouped and processed in terms of "action", and each action was composed of six or nine successive images. First, a reference image with the best quality in one action was selected. Next, the rest of the images in the action were geometrically transformed to fit in the horizontal coordinate system (expressed in azimuthal angle and elevation) of the reference image. Then, these images were median-combined to retain only the possible non-moving GEO candidates. By reverting the coordinate transformation of the positions of these GEO satellite candidates, the final coordinates could be calculated.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.382-385
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• 2004

Communication Ocean Meteorological Satellite (COMS) for the hybrid mission of meteorological observation, ocean monitoring, and telecommunication service is planned to be launched onto Geostationary Earth Orbit in 2008 according to the Korea national space program. A feasibility study on the solar constraint in the operation of the COMS meteorological imager (MI) is performed using the GOES imager hardware operation characteristics. The Earth observation areas of the MI are introduced and the observation time of the MI observation area is calculated. The sun light can enter into the MI optical system around the local midnight and impinge on the performance of the MI. The solar eclipse viewed from the satellite occurs near local midnight around the equinox. This study discusses the restriction of imaging operation time that should be considered in order to avoid the solar intrusion about local midnight and to keep acceptable image quality for the MI observation areas. This study could be useful to build the operation concept of the MI during the development of the MI.

• Journal of Astronomy and Space Sciences
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• v.28 no.4
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• pp.333-344
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• 2011

An optical tracking system has advantages for observing geostationary earth orbit (GEO) satellites relatively over other types of observation system. Regular surveying for unidentified space objects with the optical tracking system can be an early warning tool for the safety of five Korean active GEO satellites. Two strategies of positioning on the observed image of Communication, Ocean and Meteorological Satellite 1 are tested and compared. Photometric method has a half root mean square error against streak method. Also eccentricity method for initial orbit determination (IOD) is tested with simulation data and real observation data. Under 10 minutes observation time interval, eccentricity method shows relatively better IOD results than the other time interval. For follow-up observation of unidentified space objects, at least two consecutive observations are needed in 5 minutes to determine orbit for geosynchronous orbit space objects.

• Journal of Astronomy and Space Sciences
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• v.27 no.4
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• pp.337-343
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• 2010

Optical observation system provides angle-only measurement for orbit determination of space object. Range measurement can be directly acquired using laser ranging or tone ranging system. Initial orbit determination (IOD) by using angle- only data set shows discrepancy according to the measurement time interval. To solve this problem, range measurement data should be added for IOD. In this study, two-site optical observation was used to derive the range information. We have observed nine geostationary earth orbit satellites by using two-site optical observation system. The determination result of the range shows the accuracy over 99.5% compared to the results from the satellite tool kit simulation. And we confirmed that the orbit determination by the Herrick-Gibbs method with the range information obtained from the two-site observation is more accurate than the orbit determination by Gauss method with the one-site observation. For more accurate two-site optical observation, a baseline should satisfy an optimal condition of length and more precise observation system needed.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.12
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• pp.9-14
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• 2010

Using an IR (infrared) optical system of observation and research were performed long before. Nowadays satellites equipped with IR optical system observe the earth and universe. In this paper, we developed the IR optical system for main payload of the STSAT-3 (Science and Technology Satellite -3). We studied the ultra precision machining technique to fabricate FPL-53 lenses which is the IR optical material for space observation camera of the STSAT-3. DOE (Design of Experiment) was used to find best machining characteristic for FPL-53. Finally we fabricated FPL-53 aspheric lens with the form accuracy of P-V $0.36\;{\mu}m$.