• Journal of Astronomy and Space Sciences
• /
• v.18 no.2
• /
• pp.137-144
• /
• 2001

This paper presents the REA thrusters performance estimation results for the KOREASAT F1&F2 launched in 1995 The satellite tracking data obtained from the ground system from end of 1999 to beginning of the 2000 are used to estimate the thruster performance. The estimation algorithm is derived from the least square estimation theory and designed to estimate the velocity change induced by the on-boarded thruster firing as well as the orbit parameter. The estimation results show that the Koreasat F1 thruster are in bad thruster condition of 64% performance for REA when it fires in on-pulse mode. Here, the performance is defined by the ratio of the resulted velocity change to that of planned. But, in the case o( the Koreasat F2, it is found that the performance approximately reaches up to 100%, even after the 5 years of the mission.

• Journal of Astronomy and Space Sciences
• /
• v.33 no.2
• /
• pp.127-135
• /
• 2016

Inactive space objects are usually rotating and tumbling as a result of internal or external forces. KOREASAT 1 has been inactive since 2005, and its drift trajectory has been monitored with the optical wide-field patrol network (OWL-Net). However, a quantitative analysis of KOREASAT 1 in regard to the attitude evolution has never been performed. Here, two optical tracking systems were used to acquire raw measurements to analyze the rotation period of two inactive satellites. During the optical campaign in 2013, KOREASAT 1 was observed by a 0.6 m class optical telescope operated by the Korea Astronomy and Space Science Institute (KASI). The rotation period of KOREASAT 1 was analyzed with the light curves from the photometry results. The rotation periods of the low Earth orbit (LEO) satellite ASTRO-H after break-up were detected by OWL-Net on April 7, 2016. We analyzed the magnitude variation of each satellite by differential photometry and made comparisons with the star catalog. The illumination effect caused by the phase angle between the Sun and the target satellite was corrected with the system tool kit (STK) and two line element (TLE) technique. Finally, we determined the rotation period of two inactive satellites on LEO and geostationary Earth orbit (GEO) with light curves from the photometry. The main rotation periods were determined to be 5.2 sec for ASTRO-H and 74 sec for KOREASAT 1.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.30 no.8
• /
• pp.141-147
• /
• 2002

Estimation of thrusters efficiency is a very important process at the end of lifetime of a satellite. This paper introduces a technique to estimate the efficiency change of thrusters considering bubble effect for Koreasat I. During APEMAC(Automatic Pitch Error/ Momentum Adjust Control), the change in thruster efficiency is estimated to compare the attitude telemetry data of the Koreasat I with the results of the control logic using Simulink. The outcome of this study is expected to contribute to improving the operational load at the end of generic communication satellite mission.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.5 no.1
• /
• pp.60-68
• /
• 2001

Thermal Mass Method(TMM) and its accuracy, utilized in the propellant gauging system of KOREA SAT-3, are described in the paper The residual in the fuel tank system of KOREASAT-3 is simulated using TMM based on the KOREASAT-3 data package An accuracy of TMM is calculated using analytical method and compared with the error analysis Monte Carlo methods.

• Journal of Astronomy and Space Sciences
• /
• v.15 no.2
• /
• pp.427-436
• /
• 1998

The apogee manoeuvre of $KOREASAT-1{cdot}2{cdot}3$ is basic elliptical orbit transfer converting orbit plane. The KOREASAT-3 is planed for multi-burn manoeuvres using the liquid apogee engine while the $KOREASAT-1{cdot}2$ used the apogee kick motor that executes a single burn in the apogee of transfer orbit using the solid propellant. This study analyzed the multi-burn manoeuvres using the liquid apogee engine and the propellant control method and developed the simulation tools. For the purpose of precise simulation, We designed tools in the basic of orbit propagation software, COWELL5, that was developed by members of Center for Astrodynamics in Yonsei university and the results can be displayed in 3-D graphic of $STK/VO^{TM}$.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.19 no.3
• /
• pp.505-514
• /
• 1994

Koreasat spacecraft requires accurate and reliable attitude control to provide beam pointing for tenyear long communication and direction broadcasting services. This paper describes the detailed design and performance of an on-orbit normal mode attitude control subsystem for the spacecraft. Koreasat used a momentum wheel which has nominal momentum 475in-1b sec(547.6cm-kg sec) aligned with the pitch axis to control pitch attitude and provide gyroscopic stiffness in roll/yaw plane and used a 300 atm magnetic torquer to control the roll and yaw attitudes. An Earth Sensor Assembly (ESA) is used to provide pitch and roll information for the on-board micropocessor. The roll/yaw control used bang-off-bang control and while pitch axis control used proportional and integral control law. Control system errors during the operational normal mode are 0.03 deg, 0.1 deg and 0.01 deg in roll, yaw and pitch axes, respectively. Current attitude control system provides adequate control performances to capture initial attitude errors and spacecraft nutation.

• Proceedings of the Korean Institute of Communication Sciences Conference
• /
• 1991.04a
• /
• pp.1-10
• /
• 1991

• Proceedings of the IEEK Conference
• /
• 1998.10a
• /
• pp.151-154
• /
• 1998

The interference evaluation methods and criteria between the analogue TV/FM signals for BSS(Broadcasting Satellite Service) plans and the associated feeder link plans were established in WARC(World Administrative Radio Conference)-77 and 88. However, it should be applied the different interference evaluation methods and criteria of the digital TV signals from those of the analogue TV/FM signals. In this paper, the interference evaluation methods and criteria between the digital TV signals and the analogue TV/FM signals were analyzed. And also, the effects of the interference from the digital signals for Koreasat-1 into the analogue TV/FM signals for Japanese broadcasting satellite were evaluated. The amounts of EIRP reduction in the transmitting space stations were calculated to meet the interference criteria. The results showed that the digital BSS networks including Koreasat-1 would share the limited resources with the analogue BSS networks.

• 한국전산유체공학회:학술대회논문집
• /
• 2005.04a
• /
• pp.173-181
• /
• 2005

A fluid transient analysis for the propellant flow in a monopropellant propulsion system is conducted using the method of characteristics (MOC). Algebraic simultaneous equations method and Clamor's rule method utilized to drive the compatible and characteristic equations are reviewed to understand MOC more extensively. The identification of fluid transient phenomena of propulsion system of Koreasat 1 is carried out through parametric studies. Also this work describes the reason that the propulsion system of Koreasat 1 has no orifice to control flow transients or to limit the initial hydrazine flow rate for the first-pulse firing.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.31 no.1
• /
• pp.58-66
• /
• 2003

This paper discusses the practical issue of the bias estimation of the KOREASAT ground tracking data. First, a batch filter based orbit determination algorithm including the turn around range measurement in addition to the range, azimuth and elevation measurement is presented. Then the estimation performance is analyzed through simulation studies. Additionally, this paper proposes a tracking antenna bias estimation strategies using accurately tuned secondary ground tracking station. Finally the relationship between antenna biases are analyzed to give comprehensive tool for estimation results evaluation.