Woo-Kyoung Lee

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.

OPTIMAL FORMATION TRAJECTORY-PLANNING USING PARAMETER OPTIMIZATION TECHNIQUE

The present work was upported by National Research Lab(NRL) Program(2002) by the Ministry of Science and Technology, Korea. Authors fully appreciate the financial support.

RETRIEVAL OF ELECTRON DENSITY PROFILE FOR KOMPSAT-5 GPS RADIO OCCULTATION DATA PROCESSING SYSTEM

The AOPOD (Atmosphere Occultation and Precision Orbit Determination) system, the secondary payload of KOMPSAT (KOrea Multi-Purpose SATellite)-5 scheduled to be launched in 2010, shall provide GPS radio occultation data. In this paper, we simulated the GPS radio occultation characteristic of KOMPSAT-5 and retrieved electron density profiles using KROPS (KASI Radio Occultation Processing Software). The electron density retrieved from CHAMP (CHAllenging Minisatellite Payload) GPS radio occultation data on June 20, 2004 was compared with IRI (International Reference Ionosphere) - 2001, PLP (Planar Langmuir Probe), and ionosonde measurements. When the result was compared with ionosonde measurements, the discrepancies were 5 km on the peak height () and on the electron density of the peak height (). By comparing with the Laugmuir Probe measurements of CHAMP satellite (PLP), both agrees with at the height of 365.6 km.

RF ENVIRONMENT TEST ON A PROPOSED SITE FOR THE SENSOR STATION OF THE NEXT GENERATION SATELLITE NAVIGATION SYSTEM, GALILEO: I. THE RESULT OF THE TEST ON THE VICINITY OF KVN TAMLA SITE IN THE YEAR OF 2006 BY KASI

As the next generation of global satellite navigation system, the Galileo project is about to witness an initial orbit validation stage as the successful test of navigation message transmission from Giove-A in 2007. The Space Geodesy division ana the Radio Astronomy division of the Korea Astronomy & Space Science Institute had collaborated on the field survey for the Galileo Sensor Station (GSS) RF environment of the proposed site near Jeju Tamla University from August 3rd to August 5th, 2006. The power spectrums were measured in full-band and in-band (E5, E6 and L1 band) in frequency domain for 24 hours respectively. Finally, we performed a time domain analysis to characterize strong in-band interference source based on the result of the previous step.

The First Measurement of Seasonal Trends in the Equatorial Ionospheric Anomaly Trough at the CHUK GNSS Site During the Solar Maximum in 2014

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Operation of the Radio Occultation Mission in KOMPSAT-5

Korea multi-purpose satellite-5 (KOMPSAT-5) is a low earth orbit (LEO) satellite scheduled to be launched in 2010. To satisfy the precision orbit determination (POD) requirement for a high resolution synthetic aperture radar image of KOMPSAT-5, KOMPSAT-5 has atmosphere occultation POD (AOPOD) system which consists of a space-borne dual frequency global positioning system (GPS) receiver and a laser retro reflector array. A space-borne dual frequency GPS receiver on a LEO satellite provides position data for the POD and radio occultation data for scientific applications. This paper describes an overview of AOPOD system and operation concepts of the radio occultation mission in KOMPSAT-5. We showed AOPOD system satisfies the requirements of KOMPSAT-5 in performance and stability.

SHORT-TERM COMPARISON OF SEVERAL SOLUTIONS OF ELLIPTIC RELATIVE MOTION

Recently introduced, several explicit solutions of relative motion between neighboring elliptic satellite orbits are reviewed. The performance of these solutions is compared with an analytic solution of the general linearized equation of motion. The inversion solution by the Hill-Clohessy-Wiltshire equations is used to produce the initial condition of numerical results. Despite the difference of the reference orbit, the relative motion with the relatively small eccentricity shows the similar results on elliptic case and circular case. In case of the `chief` satellite with the relatively large eccentricity, HCW equation with the circular reference orbit has relatively larger error than other elliptic equation of motion does.

DETERMINATION OF INITIAL CONDITIONS FOR SATELLITE FORMATION ELYING IN ELLIPTICAL ORBITS

The initial conditions that generate bounded motion in eccentric reference orbit are determined for satellite formation flying. Because Hill`s equations cannot describe the relative motion between two satellites in eccentric orbit, a new relative dynamics utilizing the nonlinearity and eccentricity correction for Hill`s initial conditions is implemented. The constraint that matches angular rates of chief and deputy satellites is used to obtain the bounded motion between them. The constraint can be applied to satellite formation motions in eccentric orbit, since it implicates J2 perturbation due to the central body`s aspherical gravitational forces. The periodic bounded motions are analyzed for the orbit with the eccentricity of less than 0.05 and about 0.5 km relative distance between chief and deputy satellites. It is mainly illustrated that the satellite formations in small eccentric orbits can have hounded motions; consequently, the formation can be kept by matching angular rates of the satellites. These results demonstrate an useful method that reduces the cost for operating satellites by providing effective initial conditions for satellite formation flying in eccentric orbit.

DEVELOPMENT OF KAO SPACE WEATHER MONITORING SYSTEM: I. REAL-TIME DATA ACQUISITION TOOLS AND APPLICATIONS

Recently, real time data acquisition become important for space weather forecast and research. In this work, we have developed the data acquisition tools and their applications for space weather monitoring. We have developed programs to download the space weather data using IDL as well as programs to interactively display the image and data using ION (IDL on the Net). By using these tools, we have constructed the mirror site of Active Region Monitor (ARM) which summarizes several different solar activities, and developed ION programs to display TEC(Total Electron Contents) maps from GPS data at the passage of Korean satellites. At present, the KAO ARM mirror site (http://sun.kao.re.kr/arm) is successfully updated in every thirty minutes. The TEC maps from GPS data are expected to be used for monitoring the space environment of Korean satellites.