• Journal of Astronomy and Space Sciences
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• v.12 no.2
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• pp.265-274
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• 1995

The purpose of perigee kick motor firing is to place a satellite into transfer orbit and that of apogee kick motor firing is to place the satellite into geosynchonous orbit in order to increase the semi-major axis of the transfer orbit and reduce the inclination of the transfer orbit. Because apogee motor firing is always accompanied with injection errors, the satellite is not placed into geosynchonous orbit but into a near-geosynchonous orbit, also knows as a drift orbit. Thus, the orbital maneuver to correct drift orbit into gteosynchonous orbit is required, this maneuver is called the station acquisition. For reduction of expenditure and performance of mission, we estimate $\Delta$V budget and required fuel allowance for station acquisition. As the uncertainty of drift orbit by injection error of perigee and apogee kick motor firing prevents us from obtaining exact $\Delta$V budget, statistical Monte Carlo simulation technique is used in order to get optimal $\Delta$V budget and required fuel allowance with a probability of 99%. With respect to Korea satellite launched by Delta-2 launch vehicle in 1995, Monte Carlo analysis is used in order to get various orbital parameters, $\Delta$V budget and required fuel allowance for station acquisition with a probability of 99%.

• ETRI Journal
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• v.33 no.4
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• pp.487-496
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• 2011

Korea Multi-Purpose Satellite-5 (KOMPSAT-5) is the first satellite in Korea that provides 1 m resolution synthetic aperture radar (SAR) images. Precise orbit determination (POD) using a dual-frequency IGOR receiver data is performed to conduct high-resolution SAR images. We suggest orbit determination strategies based on a differential GPS technique. Double-differenced phase observations are sampled every 30 seconds. A dynamic model approach using an estimation of general empirical acceleration every 6 minutes through a batch least-squares estimator is applied. The orbit accuracy is validated using real data from GRACE and KOMPSAT-2 as well as simulated KOMPSAT-5 data. The POD results using GRACE satellite are adjusted through satellite laser ranging data and compared with publicly available reference orbit data. Operational orbit determination satisfies 5 m root sum square (RSS) in one sigma, and POD meets the orbit accuracy requirements of less than 20 cm and 0.003 cm/s RSS in position and velocity, respectively.

• Journal of Satellite, Information and Communications
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• v.11 no.1
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• pp.58-62
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• 2016

The satellite propulsion system provides the required thrust to insert a satellite into the desired orbit after separation from the launch vehicle and to control orbit inclination or compensate altitude loss due to drag after inserted into the desired orbit. The on-orbit performance of LEO satellite propulsion system according to operation mode was verified based on the results analysis for early on-orbit operation. The temperature trends of components and tubing were checked and the resultant trends were within the normal range as well.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.425-430
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• 1991

For satellite orbit determination, a satellite (K-3H) which is affected by the earth's gravitational field and the earth's atmospheric drag, the sun, and the moon is chosen as a dynamic model. The state vector include orbit parameters, uncertain parameters associated with perturbations and tracking stations. These perturbations include gravitational constant, atmospheric drag, and jonal harmonics due to the earth nonsphericity. Early orbit was obtained with given the predicted orbital parameter of the satellite. And orbit determination, which is applied to Extended Kalman Filter(EKF) for real time implementation , use the observation data which is given by satellite tracking radar system and then orbit estimation is accomplished. As a result, extended sequential estimation algorithm has a fast convergence and also indicate effectiveness for real time operation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.709-716
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• 2009

Thermal condition according to the operation attitude of a satellite in orbit would be essential to be known because the orbit attitude is a dominant factor to affect satellite thermal design. In this paper, the change in space thermal environment and the thermal effect in thermal design are studied for a low earth orbit satellite according to the yaw motion. The present satellite retains sun-pointing attitude during daylight due to the fixed type solar arrays. And it also moves along the orbit with constant yaw motion in a longitudinal axis so that a star tracker which is a star sensor for satellite's attitude control always looks into the deep space. This attitude is considered in its better visibility to the stars for a successful mission operation. Also, it is required to access the corresponding thermal effects due to the yaw motion. Therefore, we try to verify these by the thermal analysis for the satellite thermal model with the yaw motion.

• Journal of Astronomy and Space Sciences
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• v.38 no.1
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• pp.65-82
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• 2021

For the vast majority of geostationary satellites currently in orbit, station keeping activities including orbit determination and maneuver planning and execution are ground-directed and dependent on the availability of ground-based satellite control personnel and facilities. However, a requirement linked to satellite autonomy and survivability in cases of interrupted ground support is often one of the stipulated provisions on the satellite platform design. It is especially important for a geostationary military-purposed satellite to remain within its designated orbital window, in order to provide reliable uninterrupted telecommunications services, in the absence of ground-based resources due to warfare or other disasters. In this paper we investigate factors affecting the robustness of a geostationary satellite's orbit in terms of the maximum duration the satellite's station keeping window can be maintained without ground intervention. By comparing simulations of orbit evolution, given different initial conditions and operations strategies, a variation of parameters study has been performed and we have analyzed which factors the duration is most sensitive to. This also provides valuable insights into which factors may be worth controlling by a military or civilian geostationary satellite operator. Our simulations show that the most beneficial factor for maximizing the time a satellite will remain in the station keeping window is the operational practice of pre-emptively loading East-West station keeping maneuvers for automatic execution on board the satellite should ground control capability be lost. The second most beneficial factor is using short station keeping maneuver cycle durations.

• Journal of Astronomy and Space Sciences
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• v.22 no.3
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• pp.243-248
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• 2005

NORAD Two Line Element (TLE) is very useful to simplify the ground station antenna pointing and mission operations. When a satellite operations facility has the capability to determine NORAD type TLE which is independent of NORAD, it is important to analyze the applicable tracking data arcs for obtaining the best possible orbit. The applicable tracking data arcs for NORAD independent TLE orbit determination of the KOMPSAT-1 using GPS navigation solutions was analyzed for the best possible orbit determination and propagation results. Data spans of the GPS navigation solutions from 1 day to 5 days were used for TLE orbit determination and the results were used as Initial orbit for SGP4 orbit propagation. The operational orbit determination results using KOMPSAT-1 Mission Analysis and Planning System(MAPS) were used as references for the comparisons. The best-matched orbit determination was obtained when 3 days of GPS navigation solutions were used. The resulting 4 days of orbit propagation results were within 2 km of the KOMPSAI-1 MAPS results.

• Journal of Astronomy and Space Sciences
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• v.32 no.3
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• pp.229-235
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• 2015

We estimated the orbit of the Communication, Ocean and Meteorological Satellite (COMS), a Geostationary Earth Orbit (GEO) satellite, through data from actual optical observations using telescopes at the Sobaeksan Optical Astronomy Observatory (SOAO) of the Korea Astronomy and Space Science Institute (KASI), Optical Wide field Patrol (OWL) at KASI, and the Chungbuk National University Observatory (CNUO) from August 1, 2014, to January 13, 2015. The astrometric data of the satellite were extracted from the World Coordinate System (WCS) in the obtained images, and geometrically distorted errors were corrected. To handle the optically observed data, corrections were made for the observation time, light-travel time delay, shutter speed delay, and aberration. For final product, the sequential filter within the Orbit Determination Tool Kit (ODTK) was used for orbit estimation based on the results of optical observation. In addition, a comparative analysis was conducted between the precise orbit from the ephemeris of the COMS maintained by the satellite operator and the results of orbit estimation using optical observation. The orbits estimated in simulation agree with those estimated with actual optical observation data. The error in the results using optical observation data decreased with increasing number of observatories. Our results are useful for optimizing observation data for orbit estimation.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.694-697
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• 2005

A conceptual study about the angle information based orbit determination technique for a geostationary satellite was performed. With an assumption that the simultaneous observing of the earth and nearby stars is possible, we confirmed that the view angles between the earth and stars can be use as inputs for orbit determination process. By the MA TLAB simulation with least square method, the convergence is confirmed. This conceptual study was performed with the COMS for instance. This technique will be able to use as a back-up of ground station's orbit determination or a part of autonomous satellite operation.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.2
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• pp.334-343
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• 2017

The optimum design of an SAR (Synthetic Aperture Radar) satellite constellation is developed herein using a genetic algorithm. The performance of Earth observations using a satellite constellation can be improved by minimizing the maximum revisit time. Classical orbit design using analytic methods has limitations when addressing orbit dynamics due to various disturbances. To overcome this issue, an optimization technique based on a genetic algorithm is used. STK (Systems Tool Kit) is utilized to propagate the satellite orbit when considering external disturbances, and the maximum revisit time on the earth observation area is calculated. By minimizing the performance index using a genetic algorithm, the optimum orbit of the satellite constellation is designed. Numerical results are provided to demonstrate the performance of the proposed method.