Hyung-Chul Lim

Horizontal deformation in South Korea from permanent GPS network data, 2000–2003

Analysis of continuous GPS data 2000–2003 at 50 stations of the Korean GPS Network (KGN) suggests that the southern part of the Korean peninsula is tectonically more stable than other regions in the Eastern Asia. The average velocity was ∼1.5 mm/yr and the average overall strain rate was around −0.3 × 10−9str/yr. The obtained velocity field indicates the presence of anticlockwise rotation of the whole region with respect to Daejeon station (DAEJ), in the central part of South Korea. It also showed that KM-OB (Kyonggi Massif and the Okchon Basin) and YM-TB (Yeongnam Massif and Taebaeksan Basin) have left-lateral shearing movements. Both movements were confirmed by the deformation analysis of the KGN horizontal velocity field using the infinitesimal plate theory. The results show that South Korea moves toward the WNW direction with a velocity of 0.9 mm/yr with a slow anticlockwise rotation. The strain field in South Korea indicates the existence of both compression and tension. The compression and extension axes have WSW-EWE and NNW-SSE directions, respectively.

Tracking Capability Analysis of ARGO-M Satellite Laser Ranging System for STSAT-2 and KOMPSAT-5

Korea Astronomy and Space Science Institute (KASI) has developed a mobile satellite laser ranging (SLR) system called ARGO-M since 2008 for space geodesy research and precise orbit determination technologies using SLR with mm level accuracy. ARGO-M is capable of night tracking and daylight tracking for which requires spatial, spectral and time filters due to high background noises. In this study, characteristics and specifications of ARGO-M are discussed and its tracking capabilities of night and daylight tracking are analyzed for STSAT-2B and KOMPSAT-5 through link budget. Additionally false alarm and signal detection probabilities are also analyzed depending on spectral and time filters for daylight tracking for these satellites.

Analysis of Scaling Parameters of the Batch Unscented Transformation for Precision Orbit Determination using Satellite Laser Ranging Data

Korea Astronomy and Space Science Institute, Daejeon 305-348, KoreaThe current study analyzes the effects of the scaling parameters of the batch unscented transformation on precision satellite orbit determination. Satellite laser ranging (SLR) data are used in the orbit determination algorithm, which consists of dynamics model, observation model and filtering algorithm composed of the batch unscented transforma-tion. TOPEX/Poseidon SLR data are used by utilizing the normal point (NP) data observed from ground station. The filtering algorithm includes a repeated series of processes to determine the appropriate scaling parameters for the batch unscented transformation. To determine appropriate scaling parameters, general ranges of the scaling parameters of α, β, κ, λ are established. Depending on the range settings, each parameter was assigned to the filtering algorithm at regular intervals. Appropriate scaling parameters are determined for observation data obtained from several observatories, by analyzing the relationship between tuning properties of the scaling parameters and estimated orbit precision. The orbit determination of satellite using the batch unscented transformation can achieve levels of accuracy within several tens of cm with the appropriate scaling parameters. The analyses in the present study give insights into the roles of scaling parameters in the batch unscented transformation method.

Present-day relative displacements between the Jeju Island and the Korean peninsula as seen from GPS observations

We use three years data from six permanent GPS stations, in the Korean peninsula and Jeju Island, to examine the relative displacement between Jeju Island and the Korean peninsula and whether the Jeju Island lies on the Amurian Plate or not. Out of these stations, three sites, considered to be on the stable interior of the Amurian Plate (the Korean peninsula), showed relative velocities less than 1.3 mm/yr. On the other hand, the maximum velocity of the Jeju Island stations was 2.1 mm/yr with respect to DAEJ station, and the average relative velocity between the island stations and those in the main land are less than 1.7 mm/yr. By comparing these results with other velocities within the Amurian Plate, we found that the observed velocities are intra-plate. Our results are supported by geological evidences and seismological records, which claimed that the Korean peninsula and the Jeju Island are on the same plate. Hence, the Amurian Plate boundary line is considered to lie somewhere to the south of Jeju Island.

STATUS AND PROGRESS OF ARGO-M SYSTEM DEVELOPMENT

KASI (Korea Astronomy and Space Science Institute) has developed an SLR (Satellite Laser Ranging) system since 2008. The name of the development program is ARGO (Accurate Ranging system for Geodetic Observation). ARGO has a wide range of applications in the satellite precise orbit determination and space geodesy research using SLR with mm-level accuracy. ARGO-M (Mobile, bistatic 10 cm transmitting/40 cm receiving telescopes) and ARGO-F (Fixed stationary, about 1 m transmitting/receiving integrated telescope) SLR systems development will be completed by 2014. In 2011, ARGO-M system integration was completed. At present ARGO-M is in the course of system calibration, functionality, and performance tests. It consists of six subsystems, OPS (Optics System), TMS (Tracking Mount System), OES (Opto-Electronic System), CDS (Container-Dome System), LAS (Laser System) and AOS (ARGO Operation System). In this paper, ARGO-M system structure and integration status are introduced and described.

The Design Concept of the First Mobile Satellite Laser Ranging System (ARGO-M) in Korea

Korea Astronomy and Space Science Institute (KASI) launched the development project of two satellite laser ranging (SLR) systems in early 2008 after the government fund approval of the SLR systems in 2007. One mobile SLR system and one permanent SLR station will be developed with the completion of the project. The main objectives of these systems will be focused on the Space Geodetic researches. A system requirement review was held in the second half of the same year. Through the following system design review meeting and other design reviews, many unsolved technical and engineering issues would be discussed and resolved. However, the design of the mobile SLR system is a corner stone of whole project. The noticeable characteristics of Korea`s first SLR system are 1) use of light weight main mirror, 2) design of compact optical assembly, 3) use of KHz laser pulse, 4) use of commercial laser generator, 5) remote operation capability, 6) automatic tracking, 7) state of art operation system, etc. In this paper, the major user requirement and pre-defined specification are presented and discussed.

ORBIT DETERMINATION OF GPS AND KOREASAT 2 SATELLITE USING ANGLE-ONLY DATA AND REQUIREMENTS FOR OPTICAL TRACKING SYSTEM

Gauss method for the initial orbit determination was tested using angle-only data obtained by orbit propagation using TLB and SGP4/SDP4 orbit propagation model.. As the analysis of this simulation, a feasible time span between observation time of satellite resulting the minimum error to the true orbit was found. Initial orbit determination is performed using observational data of GPS 26 and Koreasat 2 from 0.6m telescope of KAO(Korea Astronomy Observatory) and precise orbit determination is also performed using simulated data. The result of precise orbit determination shows that the accuracy of resulting orbit is related to the accuracy of the observations and the number of data.

TRACKING CONTROL DESIGN USING SLIDING MODE TECHNIQUES FOR SATELLITE FORMATION FLYING

Satellite formation flying is currently an active area of research in the aerospace engineering. So it has been researched by various authors. In this study, a tracking controller using sliding mode techniques was designed to control a satellite for the satellite formation flying. In general, Hill`s equations are used to describe the relative motion of the follower satellite with respect to the leader satellite. However the modified Hill`s equations considering the perturbation were used for the design of sliding mode controller. The extended Kalman filter was applied to estimate the state vector based on the measurements of relative distance and velocity between two satellites. The simulation results show that the follower satellite tracks the desired trajectory well by thruster operations based on the sliding mode control law.

Study on the Optoelectronic Design for Korean Mobile Satellite Laser Ranging System

Korea Astronomy and Space Science Institute has been developing one mobile and one stationary satellite laser ranging system for the space geodesy research and precise orbit determination since 2008, which are called as ARGO-M and ARGO-F, respectively. They will be capable of daytime laser ranging as well as nighttime and provide the accurate range measurements with millimeter level precision. Laser ranging accuracy is mostly dependent on the optics and optoelectronic system which consists of event timer, optoelectronic controller and photon detectors in the case of ARGO-M. In this study, the optoelectronic system of ARGO-M is addressed and its critical design is also presented. Additionally, the experiment of the integrated optoelectronic system was performed in the laboratory to validate the functional operation of each component and its results are analyzed to investigate ARGO-M performance in advance.

Study on the Preliminary Design of ARGO-M Operation System

Korea Astronomy and Space Science Institute has been developing one mobile satellite laser ranging system named as accurate ranging system for geodetic observation-mobile (ARGO-M). Preliminary design of ARGO-M operation system (AOS) which is one of the ARGO-M subsystems was completed in 2009. Preliminary design results are applied to the following development phase by performing detailed design with analysis of pre-defined requirements and analysis of the derived specifications. This paper addresses the preliminary design of the whole AOS. The design results in operation and control part which is a key part in the operation system are described in detail. Analysis results of the interface between operation-supporting hardware and the control computer are summarized, which is necessary in defining the requirements for the operation-supporting hardware. Results of this study are expected to be used in the critical design phase to finalize the design process.