• Journal of Mechanical Science and Technology
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• v.15 no.2
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• pp.143-151
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• 2001

In the paper, a robust control mechanism is presented to maneuver a flexible spacecraft with the deflection reduction during large slewing operation at the same time. For deflection reduction and maneuvering of the flexible spacecraft, a control mechanism is developed with the application of stochastic optimal sliding-mode control, a linear tracking model and input shaping technique. A start-coast-stop maneuver is employed as a slewing strategy. It is shown that the control mechanism with he strategic maneuver results in better performance and is more efficient than rigid-body-like maneuver, by applying to the Spacecraft Control Laboratory Experiment (SCOLE) system in a space environment.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.1
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• pp.113-119
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• 2003

During the mission operation time, it is very important to estimate the spacecraft propellant remaining as accurately as possible. This is because the quantity of propellant is related directly to how long the satellite can be operated ín orbit. There are two different methods for spacecraft propellant gauging; the PVT method and the book-keeping method. This paper describes the characteristics and applications of these methods using the flight operation data of KOMPSAT-1. Additionally, propellant consumption rates in delta-V maneuvering and each attitude control submode are analyzed according to spacecraft operation modes. The earth search submode shows the highest propellant consumption rate.

• Journal of the Korean Institute of Telematics and Electronics B
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• v.32B no.6
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• pp.932-942
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• 1995

A spacecraft power system can be divided into two types : DET system(Direct Energy Transfer system) and PPT system(Peak Power Tracking system). In a DET system employing the regulated bus voltage control method, the battery charger and discharger are widely used for the bus voltage regulation. The battery charger has two different modes of operation. One is the bus voltage regulation mode and the other is the charge current regulation mode. The battery discharger is employed to provide the power when the spacecraft is in the earth's shadow or the sun is eclipsed. The operating mode, charging or discharging, is selected by a power control circuit. In this paper, small-signal dynamic characteristics of battery charging and discharging system are analyzed to facilitate design of control loop for optimum performance. Control loop designs in various operating modes are discussed. Anaylses are verified through experiments.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.773-776
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• 2002

The battery charger of spacecraft has two different modes of operation respectively. One is the bus voltage regulation mode and the other is the charge current regulation mode. And also the battery discharger provide the power during eclipse mode of spacecraft. In this study, a test model of the battery charger and discharger using hi-directional converter are designed and analyzed. These Battery Charger and Discharger is introduced the modular converter method that can be added the converter modules according to the load variation.

• Journal of Astronomy and Space Sciences
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• v.41 no.1
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• pp.43-60
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• 2024

Korea Pathfinder Lunar Orbiter (KPLO) is South Korea's first space exploration mission, developed by the Korea Aerospace Research Institute. It aims to develop technologies for lunar exploration, explore lunar science, and test new technologies. KPLO was launched on August 5, 2022, by a Falcon-9 launch vehicle from cape canaveral space force station (CCSFS) in the United States and placed on a ballistic lunar transfer (BLT) trajectory. A total of four trajectory correction maneuvers were performed during the approximately 4.5-month trans-lunar cruise phase to reach the Moon. Starting with the first lunar orbit insertion (LOI) maneuver on December 16, the spacecraft performed a total of three maneuvers before arriving at the lunar mission orbit, at an altitude of 100 kilometers, on December 27, 2022. After entering lunar orbit, the commissioning phase validated the operation of the mission mode, in which the payload is oriented toward the center of the Moon. After completing about one month of commissioning, normal mission operations began, and each payload successfully performed its planned mission. All of the spacecraft operations that KPLO performs from launch to normal operations were designed through the system operations design process. This includes operations that are automatically initiated post-separation from the launch vehicle, as well as those in lunar transfer orbit and lunar mission orbit. Key operational procedures such as the spacecraft's initial checkout, trajectory correction maneuvers, LOI, and commissioning were developed during the early operation preparation phase. These procedures were executed effectively during both the early and normal operation phases. The successful execution of these operations confirms the robust verification of the system operation.

• ETRI Journal
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• v.27 no.2
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• pp.140-152
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• 2005

In this paper, we present design features, implementation, and validation of a satellite simulator subsystem for the Korea Multi-Purpose Satellite-2 (KOMPSAT-2). The satellite simulator subsystem is implemented on a personal computer to minimize costs and trouble on embedding onboard flight software into the simulator. An object-oriented design methodology is employed to maximize software reusability. Also, instead of a high-cost commercial database, XML is used for the manipulation of spacecraft characteristics data, telecommand, telemetry, and simulation data. The KOMPSAT-2 satellite simulator subsystem is validated by various simulations for autonomous onboard launch and early orbit phase operations, anomaly operation, and science fine mode operation. It is also officially verified by successfully passing various tests such as the satellite simulator subsystem test, mission control element system integration test, interface test, site installation test, and acceptance test.

• Aerospace Engineering and Technology
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• v.4 no.2
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• pp.71-78
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• 2005

The purpose of FMECA is to identify parts and design whose damage can effect the mission performance and to improve the spacecraft design using these data. In consequence of this analysis, each failure mode which can be happened during operation and manufacturing period is identified, and their effects on mission performance are reviewed. In this technical report, the FMECA procedures and results for the satellite which is now under development are showed.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.467-470
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• 2004

In early 2004, KARI developed 5ft S-Band TT&C antenna for especially KOMPSAT-2 operation in LEOP phase. This paper shows system features of 5ft S-Band antenna and its test result with KOMPSAT-l. Tracking test, command uplink test and telemetry downlink test were performed. Through tests, 5ft antenna was verified to be operational in uplink and downlink with KOMPSAT series. Due to its inherent wide 3dB beam-width of about 7deg at S-Band, this antenna system can be used very effectively even though orbital information is less accurate like LEOP and spacecraft safe mode.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.107-113
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• 2000

Design configuration and performance requirements for KOMPSAT-1 propulsion system were described. Operational results of the propulsion system obtained through the satellite Launch and Early Operation Phase were scrutinized. Performance characteristics of the thrusters which are employed for spacecraft attitude control and the corresponding propellant depletion rate were analysed according to satellite operation modes. Additionally, propellant leakproof and thermal control capability were checked out from the view point of system verification. Propellant depletion rates calculated by PVT method in $\Delta$V maneuvering and each attitude control mode produce the very meaningful results for the prediction of total propellant consumption up to the end of satellite mission life.

• Journal of Satellite, Information and Communications
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• v.11 no.3
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• pp.51-57
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• 2016

Many kinds of telemetry should be monitored to check the state of spacecraft and it leads the time consumption. However, it is very important to define the status of satellite in short time because the contact number and time of low earth orbit satellite is limited. Also, on-board fault management should be prepared for non-contact operation because of the sever space environment. In this paper, on-board and ground autonomous operation method for the safety enhancement is described. Immediate fault detection and response is possible in ground by explicit anomaly detection through satellite event and error information. Also, satellite operation assistant system is proposed for ground autonomy that collect event sequence in accordance with related telemetry and recommend or execute an appropriate action for abnormal state. Critical parameter monitoring method with checking rate, mode and threshold is developed for on-board autonomous fault management. If the value exceeds the limit, pre-defined command sequence is executed.