• International Journal of Aeronautical and Space Sciences
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• 제17권4호
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• pp.622-630
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• 2016

In the operation of a low earth orbit satellite, a series of antenna commands are transmitted from a ground station to the satellite within a visibility window (i.e., the time period for which an antenna of the satellite is visible from the station) and executed to control the antenna. The window is a limited resource where all data transmission is carried out. Therefore, minimizing the transmission time for the antenna commands by reducing the data size is necessary in order to provide more time for the transmission of other data. In this paper, we propose a geometric compression method based on B-spline curve fitting using dominant points in order to compactly represent the antenna commands. We transform the problem of command size reduction into a geometric problem that is relatively easier to deal with. The command data are interpreted as points in a 2D space. The geometric properties of the data distribution are considered to determine the optimal parameters for a curve approximating the data with sufficient accuracy. Experimental results demonstrate that the proposed method is superior to conventional methods currently used in practice.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.158-165
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• 1997

The Sun interference event predictions for the KOMPSAT TT&C station were performed to analyze the frequency of the event and the impact on the TT&C link. The KOMPSAT orbit was propagated including only J2 geopotential term for maintaining the Sun-synchronism and no other perturbations were included. Local time of ascending node of the KOMPSAT satellite was set to 10h50m00s. The TT&C station was assumed to locate in Taejon and have 9 meter antenna for S-band link. One year of simulation from 1999/07/01 were performed out of 3 year of mission lifetime of KOMPSAT satellite. Total four times of Sun interference events were occurred during 1 year of simulation and those lasted about 50 seconds altogether. The C/N degradation of the TT&C system was calculated about 4dB. The Sun interference event of 50 seconds of year are 0.0076 percents of the S-band contact time when the 30 minute of contact time is assumed in a day.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2022년도 추계학술대회
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• pp.556-558
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• 2022

본 논문에서는 인공지능 알고리즘을 운용할 수 있는 고성능 소형 컴퓨터인 젯슨 나노를 기반으로 차량 추적 기능을 가진 캔위성 시스템을 제안한다. 캔위성 시스템은 캔위성과 지상국으로 구성되며, 캔위성은 대기권 내에서 낙하하며 장착된 센서를 통해 얻은 데이터를 무선통신을 이용해 지상국으로 전송한다. 기존 캔위성은 단순히 수집된 정보를 지상국에 전송하는 임무로 제한되며, 제한된 낙하 시간과 무선통신의 대역폭 제한으로 효율적인 임무 수행에는 한계가 있었다. 본 논문에서 제안하는 젯슨 나노 기반의 캔위성은 사전에 학습된 신경망 모델을 이용하여 공중에서 촬영한 영상에서 차량의 위치를 실시간으로 탐지 후, 2축 모터를 이용하여 카메라를 움직여 차량을 추적한다.

• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.51-61
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• 2014

In this work, the preliminary analysis on both the tracking schedule and measurements characteristics for the spacecraft on the phase of lunar transfer and capture is performed. To analyze both the tracking schedule and measurements characteristics, lunar transfer and capture phases' optimized trajectories are directly adapted from former research, and eleven ground tracking facilities (three Deep Space Network sties, seven Near Earth Network sites, one Daejeon site) are assumed to support the mission. Under these conceptual mission scenarios, detailed tracking schedules and expected measurement characteristics during critical maneuvers (Trans Lunar Injection, Lunar Orbit Insertion and Apoapsis Adjustment Maneuver), especially for the Deajeon station, are successfully analyzed. The orders of predicted measurements' variances during lunar capture phase according to critical maneuvers are found to be within the order of mm/s for the range and micro-deg/s for the angular measurements rates which are in good agreement with the recommended values of typical measurement modeling accuracies for Deep Space Networks. Although preliminary navigation accuracy guidelines are provided through this work, it is expected to give more practical insights into preparing the Korea's future lunar mission, especially for developing flight dynamics subsystem.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.207-210
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• 2007

A part of the big differences between LEO(Low Earth Orbit) and GEO(Geostationary Earth Orbit) satellite is that transfer orbit is used or not or what tolerance of the position on the mission orbit is permitted. That is to say, the transfer orbit is not used and the constraint of orbit position is not adapted on LEO satellite. Whereas for GEO satellite case, the transfer orbit shall be used due to the very high altitude and the satellite shall be stayed in the station keeping box which is permitted on the mission orbit. These phases are functions for AOCS mission. The aim of this paper is to introduce the AOCS hardware configuration for COMS (Communication, Ocean and Meteorological Satellite). The AOCS hardware of COMS consist of 3 Linear Analogue Sun Sensors (LIASS), 3 Bi-Axis Sun Sensors (BASS), 2 Infra-Red Earth Sensors (IRES), 3 Fiber Optical Gyroscopes (FOG), 5 momentum wheels and 14 thrusters. In this paper, each component is explained how to be used, how to locate and what relation between the AOCS algorithm and these components.

• 항공우주기술
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• 제1권1호
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• pp.117-127
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• 2002

본 논문에서는 "3단형 과학로켓 (기본형)" 의 탑재부의 구조설계에 대하여 기술하였다. 탑재부는 KSR-III 기본형의 2단에 해당하며, 로켓의 임무수행과 관련한 과학탑재부, 지상국의 자료송수신을 위한 탑재부(전자), 로켓의 자세제어를 담당하는 탑재부(자세제어)의 세부분으로 구성된다. 로켓의 임무가 성공하려면 각 탑재물이 임무수행 기간 중에 안전하게 동작해야 하며, 이를 위해서는 각 탑재부의 요구조건을 만족해야 한다. 본 연구에서는 KSR-III의 탑재부의 기본설계를 바탕으로 상세한 탑재부의 구성과 탑재물 배치를 수행하였고, 요구조건을 만족하도록 설계를 변경/ 적용하였다.

• Journal of Astronomy and Space Sciences
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• 제40권3호
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• pp.123-129
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• 2023

This paper presents an analysis of the trans-lunar trajectory insertion performance of the Korea Pathfinder Lunar Orbiter (KPLO), the first lunar exploration spacecraft of the Republic of Korea. The successful launch conducted on August 4, 2022 (UTC), utilized the SpaceX Falcon 9 rocket from Cape Canaveral Space Force Station. The trans-lunar trajectory insertion performance plays a crucial role in ensuring the overall mission success by directly influencing the spacecraft's onboard fuel consumption. Following separation from the launch vehicle (LV), a comprehensive analysis of the trajectory insertion performance was performed by the KPLO flight dynamics (FD) team. Both orbit parameter message (OPM) and orbit determination (OD) solutions were employed using deep space network (DSN) tracking measurements. As a result, the KPLO was accurately inserted into the ballistic lunar transfer (BLT) trajectory, satisfying all separation requirements at the target interface point (TIP), including launch injection energy per unit mass (C3), right ascension of the injection orbit apoapsis vector (RAV), and declination of the injection orbit apoapsis vector (DAV). The precise BLT trajectory insertion facilitated the smoother operation of the KPLO's remainder mission phase and enabled the utilization of reserved fuel, consequently significantly enhancing the possibilities of an extended mission.

• 전자공학회논문지S
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• 제34S권7호
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• pp.39-47
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• 1997

The mission of the TTC system is to acquire and process the telemetry data from the satellite and to provide mission planning and satellite control for the target stellite system. In this paper, the transmission scheme for the Tracking, Telemetry and Command(TTC) system of satelliteis described and determined according to the recommendation of CCSDS, and the channel characteristics are analyzed according to modulation method. Expecially, we introduced the concepts of carrier vs. telemetry data power ratio which causes the channel performance to degrade, and analyzed the effects of transmission performance according to the power ratio of carrier vs. telemetry data and the modulation index. The channel of the LEO TTC sytem is different with usual satellite communication system. So, we have generalized the link budget of TTC sytem for using the link budget of ground station well-known and proposed the determination method of modultion indices for improveing channel performance.

• International Journal of Aeronautical and Space Sciences
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• 제4권2호
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• pp.61-68
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• 2003

The space systems are being operated in a uncertain space environment and are desired to have autonomous capability for long periods of time without frequent telecommunications with the ground station. At the same time, requirements for new set of satellite system set of projects/systems calling for "autonomous" operations for long unattended periods of time are emerging. Since, by the nature of space systems, it is desired to perform its mission flawlessly and also it is of extreme importance to have fault-tolerant sensors and actuators for the purpose of validating science measurement data for the mission success. This studies focused on the identification/demonstration of critical technology innovations that will be applied to the Validation Control System.

• Journal of Astronomy and Space Sciences
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• 제22권3호
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• pp.243-248
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• 2005

NORAD Two Line Element (TLE) is very useful to simplify the ground station antenna pointing and mission operations. When a satellite operations facility has the capability to determine NORAD type TLE which is independent of NORAD, it is important to analyze the applicable tracking data arcs for obtaining the best possible orbit. The applicable tracking data arcs for NORAD independent TLE orbit determination of the KOMPSAT-1 using GPS navigation solutions was analyzed for the best possible orbit determination and propagation results. Data spans of the GPS navigation solutions from 1 day to 5 days were used for TLE orbit determination and the results were used as Initial orbit for SGP4 orbit propagation. The operational orbit determination results using KOMPSAT-1 Mission Analysis and Planning System(MAPS) were used as references for the comparisons. The best-matched orbit determination was obtained when 3 days of GPS navigation solutions were used. The resulting 4 days of orbit propagation results were within 2 km of the KOMPSAI-1 MAPS results.