Identification Studies of Geostationary Orbit Satellites by Using Optical Observation and Light Curve Simulation

다국어 초록 (Multilingual Abstract)

As forays into outer space have increased and become more diversified, space debris, too, has increased. Now, many countries operate a space surveillance system in order to protect its space technology and government. Even though Korea has started to utilize space surveillance system, its purpose does not go beyond simply obtaining information about satellite orbit. Henceforth, a space debris identification study is necessary in order to achieve the ultimate goals of Data Base (DB) establishment and continuous surveillance through space debris identification.
For this reason, this study, through visible light observation, has been conducted by targeting a geostationary orbit (GEO) satellite that obtains identification information. Specifically, the FENGYUN-2E satellite, Communication Ocean and Meteorological Satellite-1 (COMS-1), and Asia Broadcasting Satellite-7(ABS-7) were the focus of the study, and the observational data were utilized at Kyung Hee Astronomical Observatory, at Sobaeksan Optical Astronomy Observatory and at Chungbuk Astronomical Observatory.
The FENGYUN-2E satellite's brightness variation was analyzed through tracking mode observation, and its spinning rate was determined to be 98 rpm. The light curves of COMS-1 and ABS-7 were determined by stare mode observation, and these were compared to the light curves obtained through simulation and observations. For the light curve simulation, a rendering simulation that uses the satellites' 3D models was used. During this study, we considered satellite shape, attitude, and the material properties of the satellite surface with bidirectional scattering distribution function (BSDF) model rendering. When the observational and simulation results were compared, the two light curves showed a peak for COMS-1 and two peaks for ABS-7.
Based on the study results above, light variation analysis through stationary orbit satellite observation and simulation proved to be useful in the identification of space debris.

국문 초록 (Abstract)

우주공간에 대한 활용이 다변화 되면서 우주물체가 증가하였고 각국에서는 자국의 우주재산 보호와 정보 보호를 위해 우주물체 감시시스템을 운영한다. 우리나라 역시 우주 물체 감시시스템을 운용하기 시작하였지만 그 목적이 궤도 정보 획득에만 머물러 있다. 향후 우주물체 감시를 통한 DB구축 및 지속적 인 감시라는 최종 목표에 도달하기 위해서는 우주물체 식별 연구가 필수 적이다.
이에 본 연구에서는 광학관측을 통해 식별정보를 획득할 수 있는 정지궤도 위성을 대상으로 연구를 진행하였다. 구체적으로 FENGYUN-2E 위성과 COMS-1, ABS-7을 대상으로 연구를 진행하였으며, 관측자료는 경희대학교 천문대와 소백산 천문대 그리고 충북대 천문대의 자료를 활용하였다.
FENGYUN-2E 위성은 추적 모드 관측을 통해 광도 변화를 분석하였고, 회전율이 98 rpm 임을 확인하였다. COMS-1과 ABS-7 위성은 정지모드 관측을 통해 광도곡선을 얻었고, 동시에 광도곡선 시뮬레이션과 관측 결과를 비교하였다. 광도곡선 시뮬레이션을 위해 위성의 3차원 모델을 사용하여 렌더링 시뮬레이션을 진행하였다. 이때 위성의 구조와 자세, 그리고 재질에 따른 반사 정도를 고려하였다. 관측과 시뮬레이션 비교결과 두 광도곡선 모두 COMS-1 위성의 경우 한 개의 피크점이 나타나는 것을, ABS-7 위성의 경우 두개의 피크점이 나타나는 것을 확인할 수 있었다.
이상의 연구 결과를 통해 정지궤도 위성의 관측 및 시뮬레이션을 통한 광도곡선 분석이 우주물체를 식별하는데 유용하게 활용될 수 있음을 확인하였다.

목차 (Table of Contents)

• Chapter 1 Introduction 1
• 1.1 The necessity of identification study of space debris 1
• 1.2 Background 3
• 1.3 Scope of the study 4
• Chapter 2 Study Method 5
• 2.1 Selection of study target 5
• 2.1.1 FENGYUN series satellite 7
• 2.1.2 Communication Ocean and Meteorological Satellite-1 (COMS-1) 9
• 2.1.3 Asia Broadcasting Satellite-7 (ABS-7) 10
• 2.2 Observation Information 11
• 2.2.1 observation system 11
• 2.2.2 Observational method 13
• 1) Sidereal tracking mode 14
• 2) Stare mode 16
• 2.2.3 Date of observation 17
• 2.3 Satellite's light curve study through optical observation 18
• 2.3.1 Light curve of spin stabilization satellite 18
• 2.3.2 Light curve of three-axis stabilization satellite 19
• 2.4 Satellite's light curve study through simulation 21
• 2.4 1 Introduction of simulation 21
• 2.4.2 Satellite modeling 22
• 1) COMS-1 22
• 2) ABS-7 23
• 2.4.3 Light curve simulation 25
• 1) Initial Parameter Setting 26
• 2) Time span setting 29
• 3) Acquisition of light curve 31
• Chapter 3 Study Results 32
• 3.1 FUNGYUN satellite's brightness variation 32
• 3.2 Observed light curve of COMS-1, ABS-7 33
• 3.3 Simulated light curve of COMS-1, ABS-7 35
• Chapter 4 Discussion 36
• 4.1 Spin rate analysis of the spin stabilization satellite 36
• 4.1.1 FENGYUN-2E satellite 36
• 4.1.2 Unidentified satellite 38
• 4.2. Comparison of light curve between observation and simulation 40
• Chapter 5 Summary and Conclusion 42