• Journal of Advanced Navigation Technology
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• v.21 no.5
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• pp.428-434
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• 2017

In recent years, owing to the growing user demand for the two-way internet service based on the mobile global broadband communications, a new type of satellite terminal has been developed, known as ESIM(Earth Station in Motion). This service was required by Resolution 158(WRC-15) to study on the coexistence with the co-primary FS(Fixed Service) in 27.5-29.5 GHz as a FSS(Fixed Satellite Service) uplink. In this paper, the average received power on ESIM within -10 dB of beam width of FS and its outage probability was analyzed theoretically and also simulated to account for the azimuth angle with uniform distribution. From the results, it can be concluded that this theoretical analysis is very useful to analyze the interference from ESIM into FS based on the statistical and probabilistic method. Therefore, it is necessary to control the azimuth angle due to a moving terminal as well as the inclination angle of moving path, the operation hours, and the speed of ESIM to protect the co-primary FS.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.503-510
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• 2016

In recent years, owing to the growing user demand for the two-way internet service based on the move global broadband communications, a new type of satellite terminal has developed, known as earth station in motion (ESIM). This service was required by Resolution 158 (WRC-15) to study on the coexistence with the co-primary fixed service (FS) in 27.5-29.5 GHz as a FSS uplink. In this paper, four scenarios was introduced to account for the antenna pointing error and the azimuth for an analysis on the sharing between ESIM and FS. From analysis results, the required separation distance between two systems should be about 32~52 km according to the elevation angles of $20^{\circ}{\sim}40^{\circ}$ using thresholds of 5% and 10% outage probability. Therefore, it is necessary to control the azimuth angle due to a moving terminal as well as the pointing error of ESIM to minimize the required separation distance and to protect the co-primary FS.

• Journal of the Korean earth science society
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• v.38 no.6
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• pp.427-441
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• 2017

Theory of Earth's free oscillation is revisited. Firstly, we summarized the underlying formulations, such as the equation of motion and its conversion into numerically integrable form and then explained computational procedures including the treatment of inner core-outer core boundary and core-mantle boundary, while the latter information has not been explicitly given in most publications. Secondly, we re-calculated the periods of Earth's free oscillation modes (period >200 s) for PREM model. In doing so we acquired the values of modes missing in Dziewonski and Anderson (1981). As a case observation, one seismogram after 2011 Tohoku earthquake recorded at Daejeon, Korea (KIGAM seismic station) was briefly analyzed to identify free oscillation mode excitations on its spectra. The material in this article will be most clear guide for those on calculating the Earth's free oscillation mode.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.485-488
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• 2005

The 2nd KOrea Multi-Purpose Satellite (KOMPSAT -2) has been developed by Korea Aerospace Research Institute (KARI) since 2000. Multi Spectral Camera (MSC) is the payload for KOMPSAT -2, which will provide the observation imagery around Korean peninsula with high resolution. KOMPSAT-2 has adopted X-band Tracking System (XTS) for transmitting earth observation data to ground station. For this, data which describes and controls the pre-defined motion of each on-board X-Band antenna in XTS, must be transmitted to the spacecraft as S-Band command and it is called as Tracking Parameter Files (TPF). In this paper, the result of the development of TPF Generation S/W for KOMPSAT-2 X-Band Antenna Motion Control.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.11-18
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• 2013

Human spaceflight experience in extra-vehicular activity (EVA) is limited to two regimes: the micro-gravity environment of Earth orbit, and the lunar surface environment at one-sixth of Earth's gravity. Future human missions to low-gravity bodies, including asteroids, comets, and the moons of Mars, will require EVA techniques that are beyond the current experience base. In order to develop robust approaches for exploring these small bodies, the dynamics associated with human exploration on low-gravity surface must be characterized. This paper examines the translational and rotational motion of an astronaut on the surface of a small body, and it is shown that the low-gravity environment will pose challenges to the surface mobility of an astronaut, unless new tools and EVA techniques are developed. Possibilities for addressing these challenges are explored, and utilization of the International Space Station to test operational concepts and hardware in preparation for a low-gravity surface EVA is discussed.

• Journal of the Korean Geophysical Society
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• v.3 no.3
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• pp.193-200
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• 2000

The attenuation characteristics($Q^{-1}$) are important factors representing the physical properties of the Earth interiors, and are essential for the quantitative prediction of strong ground-motion. Based on 156 earthquakes including 76 single-station record on the seismic station located Deok-jung Ri, southeastern Korea, we made the simultaneous measurement of P and S wave attenuation($Q_P^{-1}\;and\;Q_S^{-1}$) by means of extended coda-normalization method. Estimated $Q_P^{-1}\;and\;Q_S^{-1}$ decreased from $1{\times}10^{-2}\;and\;9{\times}10^{-3}$ at 1.5 Hz to $6{\times}10^{-4}\;and\;5{\times}10^{-4}$ at 24 Hz, respectively. This can be expressed by $Q_P^{-1}=0.01\;f^{-1.07}\;and\;Q_S^{-1}=0.01\;f^{-1.03}$ which indicate strong frequency dependence.

• The Journal of Engineering Geology
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• v.31 no.3
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• pp.257-267
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• 2021

Constraints on the structure and composition of the active layer are important for understanding permafrost evolution. Soil convection owing to repeated moisture-induced freeze-thaw cycles within the active layer promotes the formation of self-organized patterned ground. Here we present the results of ground penetrating radar (GPR) surveys across a selected sorted circle near King Sejong Station, Antarctica, to better delineate the active layer and its relation to the observed patterned ground structure. We acquire GPR data in both bistatic mode (common mid-points) for precise velocity constraints and monostatic mode (common-offset) for subsurface imaging. Reflections are derived from the active layer-permafrost boundary, organic layer-weathered soil boundary within the active layer, and frozen rock-fracture-filled ice boundary within the permafrost. The base of the imaged sorted circle possesses a convex-down shape in the central silty zone, which is typical for the pattern associated with convection-like soil motion within the active layer. The boundary between the central fine-silty domain and coarse-grained stone border is effectively identified in a radar amplitude contour at the assumed active layer depth, and is further examined in the frequency spectra of the near- and far-offset traces. The far-offset traces and the traces from the lower frequency components dominant on the far-offset traces would be associated with rapid absorption of higher frequency radiowave due to the voids in gravel-rich zone. The presented correlation strategies for analyzing very shallow, thin-layered GPR reflection data can potentially be applied to the various types of patterned ground, particularly for acquiring time-lapse imaging, when electric resistivity tomography is incorporated into the analysis.

• Aerospace Engineering and Technology
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• v.11 no.1
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• pp.27-41
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• 2012

In this paper, there is analyzed the disturbances to impact on COMS attitude and the attitude error using the received telemetries in KARI ground station during normal mode of COMS. COMS was launched successfully at Kourou, French Guiana on the 26th of June, 2010. Up to now after IOT(in-orbit test), COMS is performing well the main mission to measure meteorology and ocean during about half and one year. The disturbances to impact on COMS attitude are mostly by the Sun, by the motion of payload mirror and by the spike happened during operation of earth sensor mirror and wheel. The analysis result on the other cases happened rarely during the nominal operation, is summarized.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.1
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• pp.31-37
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• 2010

Based on the analyses of satellite range measurement, the optimal operation for satellite range measurement of KOMPSAT II, which operates in the low-earth orbit, was proposed in this paper. The orbital motion of the satellite was analyzed in viewpoints of radial velocity, acceleration and speed of acceleration. Correspondingly the effects for satellite ranging signal due to satellite motion were analyzed in viewpoints of doppler phenomena, which are doppler frequency, doppler rate and speed of doppler rate. The accuracy and ambiguity probability of the satellite range measurement were quantitatively analyzed under various circumstances. The optimal operation parameters for satellite range measurement were also analyzed based on the analyzed results. The analyzed results in this paper can be utilized in design of small-sized ground station for satellite range measurement.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.388-392
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• 1996

Orbit Determination is process of obtaining values of those parameter which completely specify the motion of an orbiting body through space, based on a set of observation of the body. For the narrow land of Korea, the ground tracking system has very limited time of operation. In this connection the use of GPS for orbit determination has advantage of full autonomy on the ground station. It would be more powerful economical method for near-earth satellites. Therfore we have better to pay attention to the research of satellites of orbit determination by use of GPS. So in this research, we studied themotion of the satellites with estimation using GPS. As a result, the result of computer simulation show that good convergence and indicated effective for real operation.