• Journal of Positioning, Navigation, and Timing
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• 제8권3호
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• pp.119-127
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• 2019

COsmicheskaya Sisteyama Poiska Avariynich Sudov Search and Rescue Satellite-Aided Tracking (COSPAS-SARSAT) is an international communication support program to perform search and rescue (SAR) operations in emergency situations by using satellite signals relayed from a beacon. The legacy COSPAS-SARSAT was originally composed of low altitude and geostationary Earth orbit satellites; thus, a limited number of directional dish antennas was sufficient to cover the limited number of visible satellites at the local user terminal. However, the second generation COSPAS-SARSAT newly added the medium Earth orbit satellites, e.g., Global Navigation Satellite Systems (GNSS) to the existing system, so that the number of visible satellites increase dramatically, and the system upgrade to cover all the visible satellites is foreseen. The additional use of planned Korea Positioning System (KPS) to existing GNSS is envisaged to provide a better performance of their SAR service. This paper presents the benefits of the additional use of KPS together with the phased array antennas at the local user terminal of the COSPAS-SARSAT. This is to effectively response to the increase of the number of visible satellites. Numerical simulation is included to evaluate the performance improvement of COSPAS-SARSAT in terms of the number of visible satellites, geometry between satellites and user, and position estimation accuracy.

• 대한원격탐사학회지
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• 제29권1호
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• pp.115-121
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• 2013

천리안위성은 대한민국에서 개발한 최초의 정지궤도위성으로 궤도상 시험을 완료하고 통신, 해양, 기상임무에 대한 정상운영을 수행하고 있으며, 천리안위성의 기상탑재체는 지구 및 주변의 가시채널 및 적외채널 영상을 취득하고 있다. 본 논문에서는 천리안위성 가시채널 검출기의 성능 분석방법을 설명하고, 2년의 운영기간동안 성능 분석결과를 설명한다. 가시채널 검출기의 성능은 검출기에서 취득한 결과 및 ROLO 모델 기반의 결과를 이용해서 계산할 수 있으며, 분석을 통해서 검출기의 성능은 정상임을 확인하였다.

• 항공우주기술
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• 제12권1호
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• pp.152-162
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• 2013

달의 방사조도는 위성 가시채널 검출기의 성능을 감시하기 위해서 사용된다. 본 논문에서는 천리안위성 FDS (Flight Dynamics Subsystem)에서 생성한 태양, 달, 위성의 위치 정보를 이용하여 달의 방사조도를 계산하는 방법 및 결과를 설명한다. 계산 결과는 천리안위성 기상탑재체 가시채널 검출기의 성능저하를 검출하고 보상하기 위한 알고리즘에 적용되었다.

• 대한원격탐사학회지
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• 제37권1호
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• pp.169-176
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• 2021

The Global Space-based Inter-Calibration System (GSICS) is an international partnership sponsored by World Meteorological Organization (WMO) to continue and improve climate monitoring and to ensure consistent accuracy between observation data from meteorological satellites operating around the world. The objective for GSICS is to inter-calibration from pairs of satellites observations, which includes direct comparison of collocated Geostationary Earth Orbit (GEO)-Low Earth Orbit (LEO) observations. One of the GSICS inter-calibration methods, the Ray-matching technique, is a surrogate approach that uses matched, co-angled and co-located pixels to transfer the calibration from a well calibrated satellite sensor to another sensor. In Korea, the first GEO satellite, Communication Ocean and Meteorological Satellite (COMS), is used to participate in the GSICS program. The National Meteorological Satellite Center (NMSC), which operated COMS/MI, calculated the Radiative Transfer Model (RTM)-based GSICS coefficient coefficients. The L1P reproduced through GSICS correction coefficient showed lower RMSE and Bias than L1B without GSICS correction coefficient applied. The calculation cycles of the GSICS correction coefficients for COMS/MI visible channel are provided annual and diurnal (2, 5, 10, 14-day), but long-term evaluation according to these cycles was not performed. The purpose of this paper is to perform evaluation depending on the annual/diurnal cycles of COMS/MI GSICS correction coefficients based on the ray-matching technique using Suomi-NPP/Visible Infrared Imaging Radiometer Suite (VIIRS) data as reference data. As a result of evaluation, the diurnal cycle had a higher coincidence rate with the reference data than the annual cycle, and the 14-day diurnal cycle was the most suitable for use as the GSICS correction coefficient.

• 한국전자통신학회논문지
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• 제17권5호
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• pp.995-1002
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• 2022

위성항법시스템은 전지구에서 어디에서나 위성신호만 수신하면 수신기의 위치와 시간 정보를 획득할 수 있는 편리한 시스템이다. 하지만 항법신호는 오차를 포함하고 있고 신호의 수신 상태에 따라 수신기의 위치 오차가 발생한다. 또한, 위성들의 기하학적 배치에도 위치 오차는 영향을 받는다. 그러므로 가시위성의 개수와 상태에 따라 수신기의 위치 성능은 변화한다. 특히, 위성이 뜨거나 지는 시각에는 해당 위성의 신호 상태가 좋지 않으며 도심지에서 건물 등의 장애물로 인해 신호가 차단되는 경우에는 수신기의 위치가 변화하여 나타난다. 본 논문에서는 보정량을 추정하여 수신기가 측정한 의사거리에 반영하는 기법과 가시위성을 조정하는 기법을 이용하여 위성항법 성능을 향상하는 방법을 제안하였다. 제안된 기법을 가시위성의 개수가 빈번하게 변화하는 환경에 적용하여 위성항법 시스템의 성능향상을 검증하였다.

• 항공우주산업기술동향
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• 제7권1호
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• pp.89-96
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• 2009

이 논문에서는 지구관측용 가시광선 및 적외선 위성센서의 검보정 방법들을 소개하였다. 먼저 지구관측용으로 쓰이는 위성용 센서들에 대해 간단히 살펴보고, 이들의 검보정 방법들을 정리하였다. 위성센서 중 특히 가시광선 및 적외선 광학센서의 보정장치들을 예로 들어 이들 장치의 원리에 대해서 간략하게 설명함으로써 센서레벨에서 이루어지는 1차적인 보정원리에 중점을 두었다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.1261-1263
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• 2003

Based on twelve observational stations low meteorological visibility (LMV) data during November 2002 to April 2003, the spatial distribution of LMV over Hongkong area (113.8$^{\circ}$ E-114.4$^{\circ}$ E, 22.1$^{\circ}$ N-22.4$^{\circ}$ N) is studied, using a PCA method. Optical spectrum of NOAA-16 associated with LMV shows that the significant effect factors correlated with LMV in the leading mode are the difference or rate between the visible and near-IR channels and single visible channel. A successful retrieval of LMV is done and a regression equation with a multiple correlation coefficient of 0.67 is obtained.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.232-235
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• 2006

Using 30 days of hourly visible channel data and DIScrete Ordinate Radiative Transfer (DISORT) model (6S), Aerosol optical depth (AOD) at $0.55{\mu}m$ was retrieved over the East Asia. In contrast with the AOD retrieval using low-earth-orbit satellites such as MODIS (Moderate-Res olution Spectroradiometer) or MISR (Multiangle Imaging SpectroRadiometer), this algorithm with geostationary satellite can improve the monitoring of AOD without the limitation of temporal resolution. Due to the limited number of channels in the conventional meteorological imager onboard the geostationary satellite, an AOD retrieval algorithm utilizing a single visible channel has been introduced. This single channel algorithm has larger retrieval error of AOD than other multiple-channel algorithm due to errors in surface reflectance and atmospheric property. In this study, the effects of manifold atmospheric and surface properties on the retrieval of AOD from the geostationary satellite, are investigated and compared with the AODs from AERONET and MODIS. To improve the accuracy of retrieved AOD, efforts were put together to minimize uncertainties through extensive sensitivity tests. This algorithm can be utilized to retrieve aerosol information from previous geostationary satellite for long-term climate studies.

• Journal of Positioning, Navigation, and Timing
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• 제12권1호
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• pp.11-22
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• 2023

In this paper, we propose an efficient satellite selection method for multi-constellation GNSS. The number of visible satellites has increased dramatically recently due to multi-constellation GNSS. By the increased availability, the overall GNSS performance can be improved. Whereas, due to the increase of the number of visible satellites, the computational burden in implementing advanced processing such as integer ambiguity resolution and fault detection can be increased considerably. As widely known, the optimal satellite selection method requires very large computational burden and its real-time implementation is practically impossible. To reduce computational burden, several sub-optimal but efficient satellite selection methods have been proposed recently. However, these methods are prone to the local optimum problem and do not fully utilize the information redundancy between different constellation systems. To solve this problem, the proposed method utilizes the inter-system biases and geometric assignments. As a result, the proposed method can be implemented in real-time, avoids the local optimum problem, and does not exclude any single-satellite constellation. The performance of the proposed method is compared with the optimal method and two popular sub-optimal methods by a simulation and an experiment.

• 한국위성정보통신학회논문지
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• 제11권2호
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• pp.65-68
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• 2016

본 논문에서는 해양 환경에서 기후에 따른 가시광 무선통신 시스템에 대해 연구한다. 해양 환경에 적합한 대기 채널 모델인 Kim 모델을 이용하여 가시광 선명도에 따른 기후 조건을 맑음, 비, 폭풍, 안개로 구분하였고, OOK-NRZ 변조기법을 적용한 모의실험을 통해 기후 조건에 따른 BER 성능을 비교하였다. 또한 현장실험을 통해 실제로 가시광 통신에서 에러 비트를 측정하고 모의실험과 비교 분석을 통하여 해양 환경에서의 가시광 통신 유효성을 입증하였다.