• 한국항공우주학회지
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• 제33권11호
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• pp.41-47
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• 2005

현재 240여기의 상업용 정지궤도 통신위성이 운용 중에 있지만, GPS 등의 위치항법 위성의 고도보다 높을 뿐만 아니라 나쁜 가시성으로 인하여 중궤도 위치항법시스템을 사용할 수 없으므로 반드시 지상관제소에 의해 추적되어야 한다. 또한 지상관제소에서 관측할 경우 정지궤도 위성은 거의 움직이지 않는 것처럼 보이기 때문에 수 미터급의 정지궤도위성의 위치결정 정밀도를 높이기 위해서 충분히 멀리 떨어진 2곳 이상의 추적안테나를 사용하여야 한다. 따라서 본 논문에서는 정지궤도 위성의 궤도결정과 자동운용을 위해서 정지궤도 고도보다 높은 2일 주기의 원형궤도를 사용하는 GSPS(Geostationary Satellite Positioning System)을 제안하였다. GSPS는 지상추적소에서 정밀하게 위치가 결정된 자기 자신의 위치정보 및 시각정보, 보정데이터와 정지궤도 위성의 운용을 위한 명령을 GSPS 위성에 전송하여 정지궤도위성에 위치정보를 제공하는 기능을 한다.

• Journal of Positioning, Navigation, and Timing
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• 제13권1호
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• pp.25-34
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• 2024

The Satellite Based Augmentation System (SBAS) improves the accuracy and reliability of user positioning by transmitting the error correction and integrity information of the global navigation satellite system signal from geostationary satellites in real time. For this reason, SBAS was designed for aircraft operations and approach procedures and is now in operational or development stages in many countries. Time has passed since the construction of SBAS and many changes have occurred in the composition of the monitoring stations and the geostationary satellites. These changes have been investigated and the current operation and development status of SBAS globally are surveyed. The development and test schedules for the transition to dual frequency multi-constellation, an important topic in SBAS, are discussed.

• Journal of Positioning, Navigation, and Timing
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• 제3권4호
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• pp.149-154
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• 2014

The BeiDou is a satellite-based positioning and navigation system, which is under construction by the China Satellite Navigation Office. Until the June of 2014, the constellation of BeiDou navigation satellite system consists of 14 satellites including five geostationary earth orbit (GEO), five inclined geosynchronous earth orbit (IGSO) and four medium earth orbit (MEO). In this paper, we present the positioning results using BeiDou B1 code measurements obtained from three GNSS reference stations (BHAO, SKMA, MKPO). Combined Beidou/GPS positioning results are also compared to BeiDou and GPS only. BeiDou-only positioning errors for the east-west and north-south direction had less than 2 meter with root mean square (RMS) value. However, the positioning error for the up-down direction had larger than 10 meter at a 95% confidence level. Our results also suggest that the position precision is improved by combined BeiDou/GPS compared to BeiDou-only.

• 대한원격탐사학회지
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• 제19권3호
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• pp.181-190
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• 2003

Since the operation of the first satellite-based navigation service, satellite positioning has played an increasing role in both surveying and geodesy, and has become an indispensable tool for precise relative positioning. However, in some situations, e.g. at a low angle of elevation, the use of satellites for navigation is seriously restricted because obstacles like buildings and mountains can block signals. As a mean to resolve this problem, the quasi-zenith satellite system has been proposed as a next-generation satellite navigation system. Quasi-zenith satellite is a system which simultaneously deploys several satellites in a quasi-zenith geostationary orbit so that one of the satellites always stay close to the zenith if viewed from a specific point on the ground of East Asia. Thus, if a position measurement function compatible with CPS is installed in the quasi-zenith and stationary satellites, and these satellites are utilized together with the CPS, four satellites can be accessed simultaneously nearly all day long and a substantial improvement in position measurement, especially in metropolitan areas, can be achieved. The purpose of this paper is to evaluate the effectiveness of quasi-zenith satellite system on positioning accuracy improvement through simulation by using precise orbital information of the satellites and a three-dimensional digital map. Through this developed simulation system, it is possible to calculate the number of simultaneously visible satellites and available area for positioning without the need of actual observation. Furthermore, this system can calculate the Dilution Of Precision (DOP) and the error distribution.

• Journal of Positioning, Navigation, and Timing
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• 제9권4호
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• pp.347-356
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• 2020

In this study, Inclined Geosynchronous Orbit (IGSO) and Geostationary Orbit (GEO) of BeiDou System (BDS) and Quasi Zenith Satellite System (QZSS) satellites positions and clock errors calculated by broadcast ephemeris and compared with Multi-GNSS Experiment (MGEX) products provided by five Analysis Centers (ACs). Root Mean Square Errors (RMSE) calculated for satellite position error. The IGSO results showed that 1.82 m, 0.91 m, 1.28 m in BDS and 1.34 m 0.36 m 0.49 m in QZSS and the GEO results showed that 2.85 m, 6.34 m, 6.42 m in BDS and 0.47 m, 4.79 m, 5.82 m in QZSS in the direction of radial, along-track and cross-track respectively. RMS calculated for satellite clock error. The IGSO result showed that 2.08 ns and 1.24 ns and the GEO result showed that 1.28 ns and 1.12 ns in BDS and QZSS respectively.

• Journal of Positioning, Navigation, and Timing
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• 제5권4호
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• pp.181-191
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• 2016

A Satellite Based Augmentation System (SBAS) provides differential correction and integrity information through geostationary satellite to users in order to reduce Global Navigation Satellite System (GNSS)-related errors such as ionospheric delay and tropospheric delay, and satellite orbit and clock errors and calculate a protection level of the calculated location. A SBAS is a system, which has been set as an international standard by the International Civilian Aviation Organization (ICAO) to be utilized for safe operation of aircrafts. Currently, the Wide Area Augmentation System (WAAS) in the USA, the European Geostationary Navigation Overlay Service (EGNOS) in Europe, MTSAT Satellite Augmentation System (MSAS) in Japan, and GPS-Aided Geo Augmented Navigation (GAGAN) are operated. The System for Differential Correction and Monitoring (SDCM) in Russia is now under construction and testing. All SBASs that are currently under operation including the WAAS in the USA provide correction and integrity information about the Global Positioning System (GPS) whereas the SDCM in Russia that started SBAS-related test services in Russia in recent years provides correction and integrity information about not only the GPS but also the GLONASS. Currently, LUCH-5A(PRN 140), LUCH-5B(PRN 125), and LUCH-5V(PRN 141) are assigned and used as geostationary satellites for the SDCM. Among them, PRN 140 satellite is now broadcasting SBAS test messages for SDCM test services. In particular, since messages broadcast by PRN 140 satellite are received in Korea as well, performance analysis on GPS/GLONASS Multi-Constellation SBAS using the SDCM can be possible. The present paper generated correction and integrity information about GPS and GLONASS using SDCM messages broadcast by the PRN 140 satellite, and performed analysis on GPS/GLONASS Multi-Constellation SBAS performance and APV-I availability by applying GPS and GLONASS observation data received from multiple reference stations, which were operated in the National Geographic Information Institute (NGII) for performance analysis on GPS/GLONASS Multi-Constellation SBAS according to user locations inside South Korea utilizing the above-calculated information.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.751-756
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• 2002

Since the operation of the first satellite-based navigation services, satellite positioning has played an increasing role in both surveying and navigation, and has become an indispensable tool for precise relative positioning. However, in some situations, e.g. at a low angle of elevation, the use of satellites for navigation is seriously restricted because obstacles like buildings and mountains can block signals. As a mean to resolve this problem, the quasi-zenith satellite system has been proposed as a next-generation satellite navigation system. Quasi-zenith satellite is a system which simultaneously deploys several satellites in a quasi-zenith geostationary orbit so that one of the satellites always stay close to the zenith if viewed from a specific point on the ground of East Asia. Thus, if a position measurement function compatible with GPS is installed in the quasi-zenith and stationary satellites, and these satellites are utilized together with the GPS, four satellites can be accessed simultaneously nearly all day long and a substantial improvement in position measurement, especially in metropolitan areas, can be achieved. The purpose of this paper is to evaluate the effectiveness of quasi-zenith satellite system on positioning accuracy improvement through simulation by using precise orbital information of the satellites and a three-Dimensional digital map. Through this simulation system, it is possible to calculate the number of simultaneously visible satellites and available area of the positioning without the need of actual observation.

• ETRI Journal
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• 제30권6호
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• pp.774-782
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• 2008

An operational orbit determination (OD) and prediction system for the geostationary Communication, Ocean, and Meteorological Satellite (COMS) mission requires accurate satellite positioning knowledge to accomplish image navigation registration on the ground. Ranging and tracking data from a single ground station is used for COMS OD in normal operation. However, the orbital longitude of the COMS is so close to that of satellite tracking sites that geometric singularity affects observability. A method to solve the azimuth bias of a single station in singularity is to periodically apply an estimated azimuth bias using the ranging and tracking data of two stations. Velocity increments of a wheel off-loading maneuver which is performed twice a day are fixed by planned values without considering maneuver efficiency during OD. Using only single-station data with the correction of the azimuth bias, OD can achieve three-sigma position accuracy on the order of 1.5 km root-sum-square.

• Journal of Positioning, Navigation, and Timing
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• 제8권4호
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• pp.215-223
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• 2019

This paper analyzes navigation performances of the Korean Positioning System (KPS) constellation with respect to the orbit parameters which fulfills the specification requirements. Specifically, the satellite configuration and navigation requirements of KPS are explained, and the daily mean horizontal dilution of precision (HDOP) and satellite visibility on KPS coverage are analyzed to confirm the adequate orbit parameters. However, due to orbital slot saturation, geostationary-orbit (GEO) satellites may not be allocated in the original orbit as specified in the KPS requirements. Therefore, in a spanned window of 4 degrees from the reference longitude the navigation performance of each GEO satellite orbit is investigated.

• 한국위성정보통신학회논문지
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• 제10권4호
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• pp.95-100
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• 2015

오늘날 위성핵심기술은 동보성, 광역성, 고 정밀성, 항 재난성 등을 고려하여 다양한 정보를 제공할 수 있는 방향으로 개발되고 있다. 또한 분야별로 우주발사체, 위성 버스, 위성 탑재체, 지상국시스템 이외에 측위, 영상 등의 기술이 융합되는 방향으로 진화되고 있다. 특히 우주기술 기반 지구관측 정보서비스를 위해서는 막대한 초기 투자비용이 요구된다. 우주개발 분야와 연계되는 특성에 따라 세계 주요국은 우주개발프로그램을 통해 위성기술을 확보하고 있다. 이러한 위성기술동향 및 변화에 따라 우리나라는 차세대 정지궤도 지구관측위성 국내 자립 개발에 대한 필요성을 인정하고 효율적인 사업 추진을 위한 제반 세부추진 계획 등의 기반사항을 마련하고 있다. 우리나라에서도 위성 선진국들처럼 정지궤도 지구관측위성 개발과 관련한 개발목표의 효율적인 추진, 기술 감리 및 품질보증체계의 확립, 우주기술의기획, 평가 및 관리를 통해 위성 개발 프로그램의 추진계획, 진행과정 및 결과가 투명하게 수행되어야 한다. 이를 위해 체계적이고 지속적으로 정지궤도 지구관측위성 개발 사업을 일원화하여 관리할 수 있는 부처별 전문 조직 체계의 운영이 필요하다. 따라서 본 논문에서는 국내 외 정지궤도 위성 개발 사업의 관리체계를 기반으로 우리나라 차세대 정지궤도 지구관측위성 개발 사업관리 개선 방안을 제시한다.