Validation of Geostationary Earth Orbit Satellite Ephemeris Generated from Satellite Laser Ranging

오형직,박은서,임형철,이상률,최재동,박찬덕 한국우주과학회 2018 Journal of Astronomy and Space Sciences Vol.35 No.4

Validation of Geostationary Earth Orbit Satellite Ephemeris Generated from Satellite Laser RangThis study presents the generation and accuracy assessment of predicted orbital ephemeris based on satellite laser ranging (SLR) for geostationary Earth orbit (GEO) satellites. Two GEO satellites are considered: GEO-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) for simulational validation and Compass-G1 for real-world quality assessment. SLR-based orbit determination (OD) is proactively performed to generate orbital ephemeris. The length and the gap of the predicted orbital ephemeris were set by considering the consolidated prediction format (CPF). The resultant predicted ephemeris of GK-2B is directly compared with a pre-specified true orbit to show 17.461 m and 23.978 m, in 3D root-mean-square (RMS) position error and maximum position error for one day, respectively. The predicted ephemeris of Compass-G1 is overlapped with the Global Navigation Satellite System (GNSS) final orbit from the GeoForschungsZentrum (GFZ) analysis center (AC) to yield 36.760 m in 3D RMS position differences. It is also compared with the CPF orbit from the International Laser Ranging Service (ILRS) to present 109.888 m in 3D RMS position differences. These results imply that SLR-based orbital ephemeris can be an alternative candidate for improving the accuracy of commonly used radar-based orbital ephemeris for GEO satellites.ing This study presents the generation and accuracy assessment of predicted orbital ephemeris based on satellite laser ranging (SLR) for geostationary Earth orbit (GEO) satellites. Two GEO satellites are considered: GEO-Korea Multi-Purpose Satellite (KOMPSAT)-2B (GK-2B) for simulational validation and Compass-G1 for real-world quality assessment. SLR-based orbit determination (OD) is proactively performed to generate orbital ephemeris. The length and the gap of the predicted orbital ephemeris were set by considering the consolidated prediction format (CPF). The resultant predicted ephemeris of GK-2B is directly compared with a pre-specified true orbit to show 17.461 m and 23.978 m, in 3D root-mean-square (RMS) position error and maximum position error for one day, respectively. The predicted ephemeris of Compass-G1 is overlapped with the Global Navigation Satellite System (GNSS) final orbit from the GeoForschungsZentrum (GFZ) analysis center (AC) to yield 36.760 m in 3D RMS position differences. It is also compared with the CPF orbit from the International Laser Ranging Service (ILRS) to present 109.888 m in 3D RMS position differences. These results imply that SLR-based orbital ephemeris can be an alternative candidate for improving the accuracy of commonly used radar-based orbital ephemeris for GEO satellites.

정지궤도 위성의 자동운용을 위한 위치결정 시스템의 개념연구

이상철(Sang-Cherl Lee),주광혁(Gwanghyeok Ju),김방엽(Bang-Yeop Kim),박봉규(Bong-Kyu Park) 한국항공우주학회 2005 韓國航空宇宙學會誌 Vol.33 No.11

현재 240여기의 상업용 정지궤도 통신위성이 운용 중에 있지만, GPS 동의 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 정지궤도 위성의 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. Even more than 240 commercial geostationary communication satellites currently on orbit at the higher location than the GPS orbit altitude perform their own missions only by the support of the ground segment because of weak visibility from GPS. In addition, the orbit determination accuracy is very low without using two or more dedicated ground tracking antennas in intercontinental ground segment, since the satellite hardly moves with respect to the ground station. In this paper, we propose the GSPS(Geostationary Satellite Positioning System) in circular orbits of two sidereal days period higher than the geosynchronous orbit for orbit determination and autonomous satellite operation. The GSPS is conceived as a ranging system in that unknown positions of a geostationary satellite can be acquired from the known positions of the GSPS satellites. Each GSPS satellite transmits navigation data, clock data, correction data, and geostationary satellite command to control a geostationary satellite.

Satellite-based In-situ Monitoring of Space Weather: KSEM Mission and Data Application

오대현,김지영,이혜숙,장근일 한국우주과학회 2018 Journal of Astronomy and Space Sciences Vol.35 No.3

Many recent satellites have mission periods longer than 10 years; thus, satellite-based local space weather monitoring is becoming more important than ever. This article describes the instruments and data applications of the Korea Space wEather Monitor (KSEM), which is a space weather payload of the GeoKompsat-2A (GK-2A) geostationary satellite. The KSEM payload consists of energetic particle detectors, magnetometers, and a satellite charging monitor. KSEM will provide accurate measurements of the energetic particle flux and three-axis magnetic field, which are the most essential elements of space weather events, and use sensors and external data such as GOES and DSCOVR to provide five essential space weather products. The longitude of GK-2A is 128.2° E, while those of the GOES satellite series are 75° W and 135° W. Multi-satellite measurements of a wide distribution of geostationary equatorial orbits by KSEM/GK-2A and other satellites will enable the development, improvement, and verification of new space weather forecasting models. KSEM employs a service-oriented magnetometer designed by ESA to reduce magnetic noise from the satellite in real time with a very short boom (1 m), which demonstrates that a satellite-based magnetometer can be made simpler and more convenient without losing any performance.

정지궤도복합위성 개발 현황

최재동,박종석,장성수,박봉규,김정아,이상률 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

정지궤도복합위성개발은 천리안위성의 임무연속성 유지 및 지속적인 국내 정지궤도 위성수요에 대한 독자개발기술 확보를 위해 2011년부터 시작되었으며, 2017년 발사예정인 2A위성과 2018년 발사예정인 2B위성 2기를 동시에 개발한다. 정지궤도복합위성 2A는 천리안위성 기상관측임무의 연속성유지, 실시간 예보를 위한 짧은 관측주기, 고해상도 영상데이터 확보 및 위험기상 조기탐지등의 기상관측임무를 갖는다. 정지궤도복합위성 2B는 한반도 주변의 지속적인 해양환경 관측 및 환경오몀 관측임무를 갖는다. 해양탑재체(GOCI-Ⅱ)는 한반도 주변 해양 환경의 연속적인 관측임무를 가지며, 환경탑재체(GEMS)는 기후변화에 의해 발생되는 장ㆍ단기 환경영향 감시 및 에어로졸 및 가스등의 이동경로 추적을 통한 지구환경 오염분석을 주목적으로 한다. 본 논문에서는 현재 개발중인 정지궤도복합위성의 각 탑재체별 주요임무 분석과 위성체 및 탑재체 성능요구조건을 만족시키기 위하여 현재까지 진행된 2A/2B위성의 시스템 설계결과가 제시되었다. The GEO-KOMPSAT-2 program has been started in 2011 for the continuity of the COMS mission and to secure independent development capability to meet domestic Geostationary satellite demands. This program develop two satellites with target launch dates 2017 for GEO-KOMPSAT-2A satellite and 2018 for GEO-KOMPSAT-2B satellite simultaneously. The GEO-KOMPSAT-2A satellite has meteorological mission to maintain continuous monitoring of imagery, the high temporal resolution to improve now-casting capability, monitoring of imagery, and extracting of meteorological products with multi-spectral imager, early detection of special weather. The GEO-KOMPSAT-2B satellite have ocean monitoring mission and earth environment monitoring mission. The Geostationary Ocean Color Imager-Ⅱ(GOCI-Ⅱ) payload for ocean monitoring mission have continuous monitoring of marine environments around Korean peninsular, and Geostationary Environment Monitoring Spectrometer(GEMS) for Earth environment monitoring mission is to monitor of long-term/short-term environmental impacts driven by climate change, by tracking of transport of aerosol and gases etc. In this study, the genetic algorithm was used to get the maneuver time and delta-V for decreasing a collision probability from the approaching uncontrolled object with considering of orbit determination accuracy. In this study, it provide the mission analysis results for each payload, and also it provide the system concept design results which have been studied to meet the performance requirement specification for the 2A/2B satellites.

Availability Assessment of GPS Augmentation System Using Geostationary Satellite and QZSS in Seoul Urban Area

YOO, Kyungho,SUNG, Sangkyung,LEE, Eunsung,LEE, Sanguk,KIM, Jaehoon,LEE, Ho-Jin,LEE, Young Jae THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIEN 2009 Transactions of the Japan Society for Aeronautical Vol.52 No.177

<P>Today Global Navigation Satellite Systems (GNSS) are widely used for determining position. Within the city environment, however, in which there are many tall buildings, GNSS signals are frequently interrupted, making it difficult for users to obtain information on their exact position. This paper analyzed the availability and positioning performance of a GPS augmented system within the Seoul urban area using the Japanese QZSS (Quasi-Zenith Satellite System) and a geostationary satellite. A 3-dimensional reproduction of Seoul that was based on the 3D GIS (Geographic Information System) Digital Map and a satellite tracking algorithm using Ray-Triangle Intersection algorithm were discussed. A satellite tracking algorithm was verified through filed testing and the QZSS orbit simulator was realized using Keplerian parameter. DOP (Dilution of Precision) and availability in the urban area of Seoul were analyzed using a GPS/QZSS/geostationary satellite separately and simultaneously.</P>

천리안위성의 궤도 및 주파수 국제등록과 우주물체 등록

박응식,백명진 한국항공우주연구원 2012 항공우주산업기술동향 Vol.10 No.1

국내 독자적인 기상 및 해양관측의 필요성 증대, 통신위성의 수요충족 및 정지궤도위성 기술확보를 위하여 지난 2003년부터 천리안위성의 개발이 시작되었고 지난 2010년 6월 27일(한국시간)에 성공적으로 발사되었다. 이로써 우리나라는 세계 7번째 기상위성 보유국이면서 세계 10번째 통신위성 자체개발국이고 세계 최초의 정지궤도 해양관측위성 개발국이 되는 쾌거를 이루었다. 이러한 천리안위성의 성공적인 임무수행을 위해 사전에 소요되는 궤도 및 주파수 자원의 사전 확보가 이루어져야 하며 이와 관련된 국제등록업무를 필수적으로 수행하여야 한다. 본 논문에서는 이러한 일반적인 정지궤도위성의 궤도 및 주파수 등록절차를 소개하고, 천리안위성의 국제 위성망 등록을 위하여 지난 2004년의 사전공표자료 국제전기통신연합(ITU) 제출부터, 주변국과의 위성망 조정, 위성망 조정자료 국제등록, 위성망 통고서 등록 및 공표 현황까지의 전과정을 소개하고 추가적으로 국내외 우주물체등록 현황도 소개한다. COMS (Communication, Ocean and Meteorological Satellite) satellite development program had been started in 2003 for the enlargement of meteorological & ocean observation demand, satisfying the need of communication satellite, and the improvement of geostationary satellite technology, and had been successfully launched in 27 June 2010(korea time). Now Korea is the 7th country of owing geostationary meteorological satellite in the world, the 10th country of developing communication satellite locally in-house in the world and the first country of developing ocean monitoring geostationary satellite.COMS orbit and frequency must be secured in advance and its registration at ITU is essential for its successful mission. In this paper, general registration process for orbit and frequency and Advanced Publication Information submitted in 2004 to ITU is introduced, and the status of satellite network coordination with neighboring countries, registration of Coordination Document, Notification, and Publication is introduced. Additionally, domestic and international registration of objects launched into outer space is introduced.

GOCI와 AHI 자료를 활용한 에어로졸 광학두께 합성장 산출 연구

강형우 ( Hyeongwoo Kang ),최원이 ( Wonei Choi ),박정현 ( Jeonghyun Park ),김세린 ( Serin Kim ),이한림 ( Hanlim Lee ) 대한원격탐사학회 2021 大韓遠隔探査學會誌 Vol.37 No.5

본 연구에서는 COMS (Communication, Oceanography and Meteorology Satellite) 위성의GOCI (Geostationary Ocean Color Imager) 센서와 Himawari-8 위성의 AHI (Advanced Himawari Imager) 센서에서 산출되는 에어로졸 광학두께 (Aerosol Optical Depth; AOD)를 활용하여 단일화된 AOD 합성장을 생산하였다. 위성 간의 공간해상도와 위치좌표계가 다르기 때문에 이를 맞춰주는 전처리 작업을 선행하였다. 이후 지상관측 기반인 AERONET (AErosol RObotic NETwork)의 레벨 1.5 AOD 자료를 사용하여 각 위성과 AERONET과의 상관관계 분석 및 추세를 보간하여 기존 위성 AOD 보다 정확한 위성 AOD 자료를 생산하였다. 이후 합성과정을 진행하며 최종적으로 시공간적으로 더 완벽하고 정확한 AOD 합성장을 생산하였다. 생산된 AOD 합성장의 제곱근 평균 오차(Root Mean Square Error; RMSE)는 0.13, 평균 편향(mean bias)는 0.05로, 기존의 GOCI AOD (RMSE: 0.15, Mean bias: 0.11)와 AHI AOD (RMSE: 0.15, Mean bias: 0.05) 보다 나은 성능을 보였다. 또한 합성된 AOD는 단일위성에서 구름으로 인하여 관측되지 못한 지역에서 시공간적으로 보다 완벽하게 생산되었음을 확인하였다. In this study, fused Aerosol Optical Depth (AOD) data were produced using AOD products from the Geostationary Ocean Color Imager (GOCI) onboard Communication, Oceanography and Meteorology Satellite (COMS) satellite and the Advanced Himawari Imager (AHI) onboard Himawari-8. Since the spatial resolution and the coordinate system between the satellite sensors are different, a preprocessing was first preceded. After that, using the level 1.5 AOD dataset of AErosol RObotic NETwork (AERONET), which is ground-based observation, correlations and trends between each satellite AOD and AERONET AOD were utilized to produce more accurate satellite AOD data than the original satellite AODs. The fused AOD were found to be more accurate than the original satellite AODs. Root Mean Square Error (RMSE) and mean bias of the fused AODs were calculated to be 0.13 and 0.05, respectively. We also compared errors of the fused AODs against those of the original GOCI AOD (RMSE: 0.15, mean bias: 0.11) and the original AHI AOD (RMSE: 0.15, mean bias: 0.05). It was confirmed that the fused AODs have better spatial coverage than the original AODs in areas where there are no observations due to the presence of cloud from a single satellite.

Characteristics of the Real-Time Operation For COMS Normal Operation

조영민,박철민,김방엽,이상철,Cho, Young-Min,Park, Cheol-Min,Kim, Bang-Yeop,Lee, Sang-Cherl Korea Society of Satellite Technology 2013 한국위성정보통신학회논문지 Vol.12 No.1

Communication Ocean Meteorological Satellite (COMS) has the hybrid mission of meteorological observation, ocean monitoring, and telecommunication service. The COMS is located at $128.2{\circ}$ east longitude on the geostationary orbit and currently under normal operation service since April 2011. In order to perform the three missions, the COMS has 3 separate payloads, the meteorological imager (MI), the Geostationary Ocean Color Imager (GOCI), and the Ka-band communication payload. The satellite controls for the three mission operations and the satellite maintenance are done by the real-time operation which is the activity to communicate directly with the satellite through command and telemetry. In this paper the real-time operation for COMS is discussed in terms of the ground station configuration and the characteristics of daily, weekly, monthly, seasonal, and yearly operation activities. The successful real-time operation is also confirmed with the one year operation results for 2011 which includes both the latter part of the In-Orbit-Test (IOT) and the first year normal operation of the COMS. 통신, 해양, 기상의 세 분야 복합 임무를 수행하는 천리안위성(Communication Ocean Meteorological Satellite: COMS)은 정지궤도 동경 $128.2{\circ}$에서 2011년 4월부터 현재 정상 운영 임무를 수행하고 있다. 세 임무를 수행하기 위해 천리안위성에는 3가지 탑재체인 기상탑재체(Meteorological Imager: MI), 해양탑재체(Geostationary Ocean Color Imager: GOCI), 통신탑재체(Ka-band communication payload)가 실려 있다. 세 가지 임무 운영과 위성 유지 관리를 위해 위성 관제가 실시간 운영으로 수행된다. 위성 실시간 운영은 명령과 원격측정자료를 통해 위성과 직접 통신하는 업무이다. 본 논문에서는 천리안위성의 실시간 운영 특성으로 지상국 장비 구성과 일일, 주간, 월간, 계절별, 연간 운영 업무 특성을 논하였다. 천리안위성의 궤도상 시험(In-Orbit-Test: IOT) 말기와 정상 운영 첫 해가 포함되는 2011년의 1년간 운영 결과에 대한 토의를 통해 성공적인 실시간 운영 결과 확인도 제시하였다.

정지궤도 위성자료를 이용한 지표면 도달 태양복사량 연구

지준범 ( Joon Bum Jee ),조일성 ( Il Sung Zo ),이규태 ( Kyu Tae Lee ) 대한원격탐사학회 2013 大韓遠隔探査學會誌 Vol.29 No.1

정지기상 위성의 가시채널에서 관측되는 반사도는 지상의 일사량 관측자료와 비교하여 구름량 계산이 가능하며 이를 이용하여 지표면에 도달되는 일사량을 추정할 수 있다. 기상 센서(MI)의 경우는 675 nm 파장으로 관측된 반사도를 이용하며 해양 센서(GOCI)는 기상 센서(MI)의 관측파장과 유사한 660 nm, 680 nm 파장으로 관측된 자료를 이용할 수 있다. 연구를 위하여 태풍이 있었던 흐린 날과 맑은 날을 선정하였으며 정지위성으로부터 관측된 자료들을 이용하였다. 위성영상의 반사도가 40%이상 높은 화소들은 0.3이하의 청천지수가 나타났으며 70%이상의 태양에너지가 차폐되었다. 또한 15%이하의 반사도가 나타나는 화소들은 0.9 이상의 청천지수가 나타났으며 90%이상의 태양에너지가 지표면에 도달되었다. 계산된 일누적 일사량은 기상청 22개 관측소의 관측 일누적 일사량과 비교하였다. COMS와 MTSAT의 MI센서의 경우 관측값과 비교하여 다소 작게 계산되었으며 GOCI센서를 이용한 계산결과인 상관계수 0.96보다 낮은 0.94와 0.93의 상관성을 보였다. 그리고 일사량 관측값에 대한 RMSE는 MTSAT, COMS MI, GOCI순으로 2.21, 2.09, 2.02 MJ/m2로 나타났다. 또한 COMS GOCI센서의 일누적 계산결과를 지상 관측자료와 비교하였을 때 흐린 날과 맑은 날의 상관성은 각각 0.96과 0.86이었으며 RMSE는 1.82 MJ/m2와 2.27 MJ/m2로서 흐린 날의 상관성이 높게 나타났다. COMS 위성의 해양 센서는 기상센서와 비교하여 관측시각이 한정적이고 관측의 불연속이 있으나 높은 해상도의 이점이 있기 때문에 태양에너지 분석 등의 연구에 유용할 것으로 사료된다. The reflectance observed in the visible channels of a geostationary meteorological satellite can be used to calculate the amount of cloud by comparing the reflectance with the observed solar radiation data at the ground. Using this, the solar radiation arriving at the surface can be estimated. This study used the Meteorological Imager (MI) reflectance observed at a wavelength of 675 nm and the Geostationary Ocean Color Imager (GOCI) reflectance observed at similar wavelengths of 660 and 680 nm. Cloudy days during a typhoon and sunny days with little cloud cover were compared using observation data from the geostationary satellite. Pixels that had more than 40% reflectance in the satellite images showed less than 0.3 of the cloud index and blocked more than 70% of the solar energy. Pixels that showed less than 15% reflectance showed more than 0.9 of the cloud index and let through more than 90% of the solar energy to the surface. The calculated daily accumulated solar radiation was compared with the observed daily accumulated solar radiation in 22 observatories of the Korean Meteorological Administration. The values calculated for the COMS and MTSAT MI sensors were smaller than the observation and showed low correlations of 0.94 and 0.93, respectively, which were smaller than the 0.96 correlation coefficient calculated for the GOCI sensor. The RMSEs of MTSAT, COMS MI and GOCI calculation results showed 2.21, 2.09, 2.02 MJ/m2 in order. Comparison of the calculated daily accumulated results from the GOCI sensor with the observed data on the ground gave correlations and RMSEs for cloudy and sunny days of 0.96 and 0.86, and 1.82 MJ/m2 and 2.27 MJ/m2, respectively, indicating a slightly higher correlation for cloudy days. Compared to the meteorological imager, the geostationary ocean color imager in the COMS satellite has limited observation time and observation is not continuous. However, it has the advantage of providing high resolution so that it too can be useful for solar energy analysis.

GOCI-II 및 극궤도 위성 자료를 병합한 Chlorophyll-a 산출물생산방법 소개 및 활용 가능성 평가

신혜경,권재엽,김평중,김태호 대한원격탐사학회 2023 大韓遠隔探査學會誌 Vol.39 No.6

Satellite-based chlorophyll-a concentration, produced as a long-term time series, is crucialfor global climate change research. The production of data without gaps through the merging of timesynthesizedor multi-satellite data is essential. However, studies related to satellite-based chlorophyll-aconcentration in the waters around the Korean Peninsula have mainly focused on evaluating seasonalcharacteristics or proposing algorithms suitable for research areas using a single ocean color sensor. In this study, a merging dataset of remote sensing reflectance from the geostationary sensor GOCI-IIand polar-orbiting sensors (MODIS, VIIRS, OLCI) was utilized to achieve high spatial coverage ofchlorophyll-a concentration in the waters around the Korean Peninsula. The spatial coverage in theresults of this study increased by approximately 30% compared to polar-orbiting sensor data, effectivelycompensating for gaps caused by clouds. Additionally, we aimed to quantitatively assess accuracythrough comparison with global chlorophyll-a composite data provided by Ocean Colour Climate ChangeInitiative (OC-CCI) and GlobColour, along with in-situ observation data. However, due to the limitednumber of in-situ observation data, we could not provide statistically significant results. Nevertheless,we observed a tendency for underestimation compared to global data. Furthermore, for the evaluation ofpractical applications in response to marine disasters such as red tides, we qualitatively compared ourresults with a case of a red tide in the East Sea in 2013. The results showed similarities to OC-CCI ratherthan standalone geostationary sensor results. Through this study, we plan to use the generated data forfuture research in artificial intelligence models for prediction and anomaly utilization. It is anticipatedthat the results will be beneficial for monitoring chlorophyll-a events in the coastal waters around Korea.