• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제31권9호
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• pp.64-74
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• 2003

This paper proposes a new autonomous stationkeeping system suitable for geostationary satellite and conducts computer simulation to verify the proposed algorithm. The proposed onboard system receives pseudo-range signal from ground equipments located at two different position with long baseline, determines the orbit error in realtime and generates orbit control commands. For minimized onboard stationkeeping logic and better reliability, the orbit controller is designed to generate control signal to have the orbit roughly follow predetermined reference range data which is generated through ground based computer simulation. The reference range data is assumed to be uploaded with time tag. A simple orbit controller is proposed which combines the reference $\Delta$V and feedback control signal. Finally, the performance of the proposed system is verified through the computer simulations.

• Aerospace Engineering and Technology
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• 제12권2호
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• pp.40-47
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• 2013

GEO-KOMPSAT2 shall be designed to produce higher quality of image than that of COMS, and this requires the ground system to provide orbit data with high accuracy; better than 2km which is sort of high accuracy when it comes to geostationary satellite. For GEO-KOMPSAT2, KARI is planning to use ranging data for orbit determination, obtained from two ranging stations located in KARI and oversea country with long longitudinal baseline. This paper estimated achievable orbit determination accuracy using covariance analysis under assumption of using two ranging stations; SOC and available secondary tracking stations located in oversea countries. In addition to covariance analysis, in order to validate the analysis, the Monte-Carlo simulation has been performed and compared to the covariance analysis.

• Journal of the Korea Institute of Information and Communication Engineering
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• 제24권1호
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• pp.15-21
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• 2020

In this paper, the observation performance of the electro-optical telescope system which surveils the unknown space objects, is analyzed by the Modeling & Simulation(M&S). The operation concept for the observation of the unknown space objects using two telescope systems is considered and the M&S models are constructed. Based on the operation concept for observing the unknown space objects, the estimated orbit is generated by Initial Orbit Determination(IOD) and the observation performance is analyzed according to the offset compensation cycle for the estimated orbit. The result of the M&S based analysis in this paper shows that the observation performance increases with the shorter offset compensation cycle, and decreases with the longer offset compensation cycle. Therefore, to improve the performance of the telescope system which surveils the unknown space objects, the observation system with accurate initial orbit determination or shorter offset compensation cycle should be designed and constructed.

• Journal of Astronomy and Space Sciences
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• 제34권3호
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• pp.225-235
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• 2017

The energy balance in a satellite needs to be designed properly for the satellite to safely operate and carry out successive missions on an orbit. In this study, an analysis program was developed using the MATLAB(R) graphic user interface (GUI) for nanosatellites. This program was used in a simulation to confirm the generated power, consumed power, and battery power in the satellites on the orbit, and its performance was verified with applying different satellite operational modes and units. For data transmission, STK(R)-MATLAB(R) connectivity was used to send the generated power from STK(R) to MATLAB(R) automatically. Moreover, this program is general-purpose; therefore, it can be applied to nanosatellites that have missions or shapes that are different from those of the satellites in this study. This power simulation tool could be used not only to calculate the suitable power budget when developing the power systems, but also to analyze the remaining energy balance in the satellites.

• Proceedings of the KSRS Conference
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.604-607
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• 2005

All CCD pixels do not react uniformly even if the light of same radiance enters into the camera. This comes from the different camera optical characteristics, the read-out characteristics, the pixel own characteristics and so on. Usually, the image data of satellite camera can be corrected by the various image-processing methods in the ground. However, sometimes, the in-orbit correction is needed to get the higher quality image. Especially high frequency pixel correction in the middle of in-orbit mission is needed because the in-orbit data compression with the high frequency loss is essential to transmit many data in real time due to the limited RF bandwidth. In this case, this high frequency correction can prevent have to have any unnecessary high frequency loss. This in-orbit correction can be done by the specific correction table, which consists of the gain and the offset correction value for each pixel. So, it is very important to get more accurate correction table for good correction results. This paper shows the new algorithm to get accurate pixel correction table. This algorithm shall be verified theoretically and also verified with the various simulation and the test results.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1999년도 제14차 학술회의논문집
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• pp.238-243
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• 1999

Minimum-fuel and -time orbit transfer are two major goals of the satellite trajectory optimization. In this paper, we consider satellites in two coplanar elliptic orbits when the apsidal lines coincide, and analytically find the conditions for the two-impulse minimum-time transfer orbit using Lambert's theorem. The transfer time is a decreasing function of a variable related to the transfer orbit's semimajor axis in the minimum-time case. In the minimum-time case, there is no unique minimum-time solution, but there is a limiting solution. However, there exists a unique solution in the case of minimum-fuel transfer, fur which we find analytically the necessary and sufficient conditions. As a special case, we consider when the transfer angle is one hundred and eighty degrees. In this case, we show that we obtain the classical fuel-optimal Hohmann transfer orbit. We also derive the Hohmann transfer rime and delta-velocity equations from more general equations, which are obtained using Lambert's theorem. We note the tradeoff between minimum-time and - fuel transfer. An optimal coplanar orbit maneuver algorithm to trade off the minimum-time goal against the minimum-fuel goal is proposed. Finally, the numerical simulation results are given to demonstrate the derived theory and the algorithm.

• International Journal of Aeronautical and Space Sciences
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• 제1권2호
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• pp.43-49
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• 2000

The Global Positioning System (GPS) is becoming more attractive navigation means for LEO (Low Earth Orbit) spacecraft due to the data accuracy and convenience for utilization. The anomalies such as serious variations of Dilution-Of-Precision (DOP), loss of infrequent 3-dimensional position fix, and deterioration of instantaneous accuracy of position and velocity data could be observed, which have not been appeared during the ground testing. It may cause lots of difficulty for the processing of the orbit control algorithm using the GPS data. In this paper, the characteristics of the GPS data were analyzed according to the configuration of GPS receiver such as position fix algorithm and mask angle using GPS navigation data obtained from the first Korea Multi-Purpose Satellite (KOMPSAT). The problem in orbit tracking using GPS data, including the infrequent deterioration of the accuracy, and an efficient algorithm for its countermeasures has also been introduced. The reliability and efficiency of the modified algorithm were verified by analyzing the effect of the results between algorithm simulation using KOMPSAT flight data and ground simulator.

• The Journal of Korean Institute of Communications and Information Sciences
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• 제25권5A호
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• pp.641-650
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• 2000

The effects of noise and doppler for low orbit satellite range measurement using tone method are represented in this paper. Also the optimal noise bandwidth of range signal detection circuit which is used for range measurement system of KOMPSAT is proposed. Based on the effects of satellite orbit parameters via the deduction of dynamic motion characteristics of low orbit satellite and signal to noise spectral density of range measurement signal, the effects of noise and doppler for range measurement system are analyzed. The effect of satellite link noise is decreased, but the effect for doppler is increased as the PLL noise bandwidth of range signal detection circuit is increased. The validation of analyzed effect is verified via comparison of measurement results of KOMPSAT's range measurement system and simulation results in environments of low orbit satellite.

• Aerospace Engineering and Technology
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• 제10권2호
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• pp.65-73
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• 2011

After launch, in order to inject the geostationary satellite into its operational orbit, the perigee altitude are forced to be raised to geostationary altitude by firing onboard LAE(Liquid Apogee Engine) at apogee of the transfer orbit. In this process, the LAE burn is divided into three or four separated burns in order to control the orbit very precisely by giving feedback the determined orbit informations and to inject the satellite in predefined longitude. This paper proposes an algorithm to determine LAE firing time slots and ${\Delta}V$ vectors under assumption of impulsive LAE burning, and additionally, a method to compensate errors induced by continuous burning. And computer simulations have been performed to validate proposed algorithms.

• Journal of Advanced Navigation Technology
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• 제8권2호
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• pp.155-162
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• 2004

Recently, significant interest is shown to creation rather inexpensive global systems communications on base of Low-Earth-Orbit Satellite Networks (LEOSN). One of problems of design and creation LEOSN is development of the stream control methods and estimation it's efficiency in such networks. The given problem is complicated, that the topology of the satellite networks varies in time. It essentially hinders the analytical decision of the given problem. An effective way of overcoming of these difficulties is simulation modeling. For realization of research experiments on learning the information streams routing algorithms in LEOSN a special program complex SANET was developed. In the given paper principles of development of LEOSN simulation models and architecture of the manager by the process of a simulation modeling of the unit are considered. Methods of promotion of modeling time and architecture of a simulator complex offered in the article allow to boost essentially efficiency of simulation analysis and to ensure simulation modeling of the satellite networks consisting of several hundreds space vehicles.