• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.4
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• pp.354-363
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• 2012

Now there are a lot of expired satellites or space debris around the earth orbit and they threaten the operating satellites and manned space missions. KOMPSAT-2 that scheduled to operate the mission by July, 2013 also has to consider the space debris. This paper introduces the '25 years rules' that must be re-entered within 25 years after the space mission for LEO satellites and describes the removal trajectory design that satisfies the '25 years rules' and minimizes fuel consumption. And this paper suggests monte-carlo simulation for risk analysis that causes the approaching object to the removal trajectory. The result shows that the collision probability of worst case presents 6.0741E-07 and it need to more analysis about precise satellite safety during removal maneuver because there is no information about the object size that approaching to the satellites.

• Journal of Astronomy and Space Sciences
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• v.25 no.2
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• pp.167-180
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• 2008

The resolution of Earth images taken from a satellite has close relation with satellite's altitude. If a satellite has lower altitude, it gets a picture having better resolution. However the satellite will be exposed to heavier air drag and will spend more fuel to maintain its altitude for a desired mission. Therefore, in this study, the required fuel to maintain very low earth orbit(LEO) with severe air drag is analyzed using optimization method such as collocation method. The required fuel to maintain the low altitude has significantly increased as the mission altitude is lowered and the solar activity is maximized. This study also shows that the fuel reduced by increasing the period of the satellite maneuver is very small, and that slightly increasing the satellite's mission altitude is much effective in reducing the amount of fuel to maintain its altitude. The calculated fuel to maintain very low earth orbit in this study would give useful information in planning the budget of fuel and cost for LEO satellites.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.6
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• pp.455-466
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• 2020

In this study, we built a thermal model for SNIPE 6U nano-satellite which has scientific mission for measuring science data in near Earth space environment and described thermal design based on the thermal model. And the validity of the thermal design was verified through the on-orbit thermal analysis. The thermal design was carried out mainly on the passive thermal control techniques such as surface finishes, insulators, and thermal conductors in consideration of the characteristics of the nano-satellite. However, the components with narrow operating temperature range and directly exposed to the orbital thermal environments, such as a battery and thrusters, are accomodated with heaters to satisfy the temperature requirements. On-orbit thermal analysis conditions are based on the basic orbital conditions of the satellite, and thermal analysis was performed for Normal mode, Launch & Early Orbit Phase (LEOP), Safehold mode, and Maneuver mode which are classified by the power consumption and the attitude of the satellite according to the mission scenario. The analysis results for each mode confirmed that every component satisfies the temperature requirement. In addition, the heater capacity and duty cycle of the battery and thruster were calculated through the analysis results of the Safehold mode.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.76-82
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• 2006

The Mission Control System for KOMPSAT-2 was developed by ETRI and is being operated at Satellite Control Center at KARI to monitor and control KOMPSAT-2 (KOrea Multi-Purpose Satellite) which was launched in July 28th, 2006. MCE provides the functions such as telemetry reception and processing, telecommand generation and transmission, satellite tracking and ranging, orbit prediction and determination, attitude maneuver planning, satellite simulation, etc. KOMPSAT-2 is the successor of KOMPSAT-1 which is an earth-observation satellite. KOMPSAT-2 has higher resolution image taking ability due to MSC (Multi Spectral Camera) payload in the satellite and precise orbit and attitude determination by Mission Control System. It can produce one meter resolution image compared to six meter resolution image by KOMPSAT-1.

• Journal of Astronomy and Space Sciences
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• v.23 no.3
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• pp.245-258
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• 2006

In this paper, an automation algorithm of analyzing and scheduling the station-keeping maneuver is presented for Communication, Ocean and Meteorological Satellite (COMS). The perturbation analysis for keeping the position of the geostationary satellite is performed by analytic methods. The east/west and north/south station-keeping maneuvers we simulated for COMS. Weekly east/west and biweekly north/south station-keeping maneuvers are investigated for a period of one year. Various station-keeping orbital parameters are analyzed. As the position of COMS is not yet decided at either $128.2^{\circ}E\;or\;116.0^{\circ}E$, both cases are simulated. For the case of $128.2^{\circ}E$, east/west station-keeping requires ${\Delta}V$ of 3.50m/s and north/south station-keeping requires ${\Delta}V$ of 52.71m/s for the year 2009. For the case of $116.0^{\circ}E,\;{\Delta}V$ of 3.86m/s and ${\Delta}V$ of 52.71m/s are required for east/west and north/south station-keeping, respectively. The results show that the station-keeping maneuver of COMS is more effective at $128.2^{\circ}E$.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.51-61
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• 2014

In this work, the preliminary analysis on both the tracking schedule and measurements characteristics for the spacecraft on the phase of lunar transfer and capture is performed. To analyze both the tracking schedule and measurements characteristics, lunar transfer and capture phases' optimized trajectories are directly adapted from former research, and eleven ground tracking facilities (three Deep Space Network sties, seven Near Earth Network sites, one Daejeon site) are assumed to support the mission. Under these conceptual mission scenarios, detailed tracking schedules and expected measurement characteristics during critical maneuvers (Trans Lunar Injection, Lunar Orbit Insertion and Apoapsis Adjustment Maneuver), especially for the Deajeon station, are successfully analyzed. The orders of predicted measurements' variances during lunar capture phase according to critical maneuvers are found to be within the order of mm/s for the range and micro-deg/s for the angular measurements rates which are in good agreement with the recommended values of typical measurement modeling accuracies for Deep Space Networks. Although preliminary navigation accuracy guidelines are provided through this work, it is expected to give more practical insights into preparing the Korea's future lunar mission, especially for developing flight dynamics subsystem.

• Current Industrial and Technological Trends in Aerospace
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• v.7 no.1
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• pp.97-104
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• 2009

Successful separation of satellites from launch vehicles and release its appendages such as solar arrays and antennas are one of the most important tasks for mission accomplishment during in-orbit maneuver. Especially, specific release devices called NEA(Non-Explosive Actuator) have been widely adopted to perform safe separation and release due to its outstanding performance of low functional shock (below 500g), no contamination and easy handing as opposed to the pyroshock device. In the paper, various kinds of NEA and its history of development are reviewed along with a summary on the domestic research trend.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.7
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• pp.586-593
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• 2014

The CNUSAIL-1 project aims to develop and operate a 3U-sized cube satellite with solar sail mechanism. The primary mission is to successfully deploy the solar sail in a low earth orbit, and the secondary mission is to collect the scientific data for the effect of the solar sail deployment and operation on orbit maneuver and attitude change of the cube satellite. For this, the bus system will collect and transmit the dynamic data of the satellite and the visual images of the solar sail operation. This paper describes solar sail mission and conceptual design of CNUSAIL-1. The actuation/operation of the solar sail and the bus system are preliminarily designed in terms of attitude control system, communication system, electrical power system, command and data handling system, structure and thermal control system is designed.

• Journal of Aerospace System Engineering
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• v.13 no.3
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• pp.23-31
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• 2019

The design requirements of modern satellites vary depending on the purpose of operation. Like conventional medium and large-scale satellites, small satellites which operate on low orbit may also serve military purposes. As a result, there is increased demand for high-resolution photos and videos and multi-target observation becomes important. The most important design parameter for multi-target observation is the satellites' maneuverability. For increased maneuverability, the miniaturization is required to increase the stiffness of the satellite as this decreases the mass moment of inertia of the satellite. In the case of a solar panel having relatively low stiffness compared to the satellites' body, vibrations are generated when the attitude maneuver is performed, which greatly influences the image acquisition. For verification of such vibrational characteristics, the satellites is modeled as a reduced model, and experimental zig for simulating attitude maneuver is introduced. A rigidity simulator for simulating the stiffness of the satellite is also proposed. Additionally, the objective of the experimental method is to simulate the maneuvering angle of the satellite based on the winding length of the wire using a step motor, and to experimentally verify the vibration characteristics of the satellite body and the solar panel generated during the maneuvering test.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.1
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• pp.28-35
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• 2009

This paper derives the equation of coordinated attitude formulation taking into account the orbital dynamics of a target vehicle and the attitude of a tracking satellite in geostationary orbit. The coordinated attitude is always to communicate with the ground station during the target tracking. Because the tracking satellite could perform high angle maneuver, MRP parameters having no singular point are used. Also for the sequential tracking of several target vehicles, the equation automatically making a coordinated attitude is suggested. Coordinated attitude flying and sequential tracking are confirmed through simulations. In short, this paper shows that a satellite could track a target vehicle and communicate with ground station simultaneously using the derived equation of coordinated attitude even though without a accuracy sensor.