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GPS-Based Orbit Determination for KOMPSAT-5 Satellite
황유라,Byoung-Sun Lee,김영록,Kyoung-Min Roh,Ok-Chul Jung,김해동 한국전자통신연구원 2011 ETRI Journal Vol.33 No.4
Korea Multi-Purpose Satellite-5 (KOMPSAT-5) is the first satellite in Korea that provides 1 m resolution synthetic aperture radar (SAR) images. Precise orbit determination (POD) using a dual-frequency IGOR receiver data is performed to conduct high-resolution SAR images. We suggest orbit determination strategies based on a differential GPS technique. Double-differenced phase observations are sampled every 30 seconds. A dynamic model approach using an estimation of general empirical acceleration every 6 minutes through a batch least-squares estimator is applied. The orbit accuracy is validated using real data from GRACE and KOMPSAT-2 as well as simulated KOMPSAT-5 data. The POD results using GRACE satellite are adjusted through satellite laser ranging data and compared with publicly available reference orbit data. Operational orbit determination satisfies 5 m root sum square (RSS) in one sigma, and POD meets the orbit accuracy requirements of less than 20 cm and 0.003 cm/s RSS in position and velocity, respectively.
Cross-coupling 효과를 고려한 해석적 방법에 의한 위치유지조정 전략
황유라,이병선 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11
정지궤도위성은 주기적으로 동서방향과 남북방향으로 위치유지 조정을 수행하여 위성이 임무 구간 내에 위치하도록 해야 한다. 동서방향 위치유지조정은 이심률 벡터와 경도 변화률에 의해 기동 시각과 속도 증분량을 계산하는 방법이고, 남북방향 위치유지조정은 경사각 벡터를 조정하여 수행한다. 이 논문에서는 남북 방향과 동서 방향 기동에 대한 crosscoupling 효과를 고려한 속도증분량을 계산하여 임무 구간 내에 위성이 유지 되는지 시뮬레이션 결과를 통하여 확인하였다. Geostationary satellites should keep the position within a given longitude mission boundary by performing stationkeeping (SK) periodically. East-West (EW) SK controls eccentricity vector and longitude drift by adding velocity increments in specific calculated time. North-South (NS) SK conducts inclination vector control. In this paper we demonstrate that the satellite is within mission boundary for EW and NS SK considering cross-coupling effect.
수용성 고분자 용액 처리 시 온도 및 첨가제가 토양 건조에 미치는 영향
황유라,심지연,배선영 서울여자대학교 자연과학연구소 2013 자연과학연구논문집 Vol.25 No.-
Dust particles have been generated from the soil exposed to the atmosphere via desiccation process. There are several ways to reduce dust generation from the exposed ground. Among various means, polymer solution has been received a great attention due to easy application and effectiveness of its results. In this study, the soil obtained from the ground in Seoul Women’s University was mixed with 3 different polymer solutions; polyacrylamide, polyacrylic acid and polyacrylamide copolymer with polyacrylic acid. In addition, sodium lauryl sulfate, a surfactant which helps the aqueous polymer molecules penetrate into the soil particles and adsorb to their surfaces and 1,6-diisocyanatohexane, which is an additive to solidify the soil particles for the strength enhancement were mixed to investigate their effects on soil desiccation. The desiccation durations were 44 days at room temperature and 12 days at 50oC, respectively. The half-lives and desiccation rate constant have been determined from the 1st order reaction. As a result of desiccation at room temperature, soil mixed with 1% polyacrylamide, surfactant and an additive showed 8.27 days while 3.33 days with water as a control. It was found that the surfactant enhanced the sorption of polymer molecules in aqueous phase to reduce the water evaporation from the surface.