• Title/Summary/Keyword: Satellite dynamic model.

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Improved Gradient Direction Assisted Linking Algorithm for Linear Feature Extraction in High Resolution Satellite Images, an Iterative Dynamic Programming Approach

  • Yang, Kai;Liew, Soo Chin;Lee, Ken Yoong;Kwoh, Leong Keong
    • Proceedings of the KSRS Conference
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    • 2003.11a
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    • pp.408-410
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    • 2003
  • In this paper, an improved gradient direction assisted linking algorithm is proposed. This algorithm begins with initial seeds satisfying some local criteria. Then it will search along the direction provided by the initial point. A window will be generated in the gradient direction of the current point. Instead of the conventional method which only considers the value of the local salient structure, an improved mathematical model is proposed to describe the desired linear features. This model not only considers the value of the salient structure but also the direction of it. Furthermore, the linking problem under this model can be efficiently solved by dynamic programming method. This algorithm is tested for linear features detection in IKONOS images. The result demonstrates this algorithm is quite promising.

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GPS Satellite Orbit Prediction Based on Unscented Kalman Filter

  • Zheng, Zuoya;Chen, Yongqi;Xiushan, Lu;Zhixing, Du
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.1
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    • pp.191-196
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    • 2006
  • In GPS Positioning, the error of satellite orbit will affect user's position accuracy directly, it is important to determine the satellite orbit precise. The real-time orbit is needed in kinematic GPS positioning, the precise GPS orbit from IGS would be delayed long time, so orbit prediction is key to real-time kinematic positioning. We analyze the GPS predicted ephemeris, on the base of comparison of EKF and UKF, a new orbit prediction method is put forward based on UKF in this paper, the result shows that UKF improves the orbit predicted precision and stability. It offers a new method for others satellites orbit determination as Galileo, and so on.

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Analysis, Modeling and Compensation of Dynamic Imbalance Error for a Magnetically Suspended Sensitive Gyroscope

  • Xin, Chaojun;Cai, Yuanwen;Ren, Yuan;Fan, Yahong;Xu, Guofeng;Lei, Xu
    • Journal of Magnetics
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    • v.21 no.4
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    • pp.529-536
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    • 2016
  • Magnetically suspended sensitive gyroscopes (MSSGs) provide an interesting alternative for achieving precious attitude angular measurement. To effectively reduce the measurement error caused by dynamic imbalance, this paper proposes a novel compensation method based on analysis and modeling of the error for a MSSG. Firstly, the angular velocity measurement principle of the MSSG is described. Then the analytical model of dynamic imbalance error has been established by solving the complex coefficient differential dynamic equations of the rotor. The generation mechanism and changing regularity of the dynamic imbalance error have been revealed. Next, a compensation method is designed to compensate the dynamic imbalance error and improve the measurement accuracy of the MSSG. The common issues caused by dynamic imbalance can be effectively resolved by the proposed method in gyroscopes with a levitating rotor. Comparative simulation results before and after compensation have verified the effectiveness and superiority of the proposed compensation method.

Precision Orbit Propagator for Low Earth Orbiters (저궤도 위성용 정밀궤도 계산모델 개발)

  • Kim, Jeong-Rae;Noh, Jeong-Ho;Kee, Chang-Don
    • Journal of Advanced Navigation Technology
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    • v.16 no.6
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    • pp.900-909
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    • 2012
  • Low Earth orbit satellites with satellite navigation receiver use onboard navigation filters for filtering measurement signals and for orbit prediction under signal loss. Precision satellite dynamic models, core of the navigation filter, are studied and a computation program is developed. Gravity acceleration, precision coordinate transform, third-body gravity, atmospheric drag, and solar radiation pressure models are combined into an orbit prediction algorithm, and a proven precision orbit determination software is used to validate the program. Orbit prediction accuracy is analyzed with simulated and flight orbit data. The program meets an accuracy level for onboard real-time navigation filter.

Extraction of Geomagnetic Field from KOMSAT-1 Three-Axis Magnetometer Data

  • Hwang, Jong-Sun;Lee, Sun-Ho;Min, Kyung-Duck;Kim, Jeong-Woo
    • Proceedings of the KSRS Conference
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    • 2002.10a
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    • pp.242-242
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    • 2002
  • The Earth's magnetic field acquired from KOMPSAT-1's TAM (Three-Axis Magnetometer) between June 19th and 21st 2000 was analyzed. The TAM, one of the KOMPSAT-1's Attitude and Orbit Control Subsystems, plays an important role in determining and controlling the satellite's attitude. This also can provide new insight on the Earth's magnetic field. By transforming the satellite coordinate from ECI to ECEF, spherical coordinate of total magnetic field was achieved. These data were grouped into dusk (ascending) and dawn (descending) data sets, based on their local magnetic times. This partitioning is essential for performing 1-D WCA (Wavenumber Correlation Analysis). Also, this enhances the perception of external fields in the Kompsat-1's TAM magnetic maps that were compiled according to different local. The dusk and dawn data are processed independently and then merged to produce a total field magnetic anomaly map. To extract static and dynamic components, the 1-D and 2-D WCAs were applied to the sub-parallel neighboring tracks and dawn-dusk data sets. The static components were compared with the IGRF, the global spherical harmonic magnetic field model. The static and dynamic components were analyzed in terms of corefield, external, and crustal signals based on their origins.

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Spin Axis Determination of Defunct GLONASS Satellites Using Photometry Observation

  • Lee, Jeeho;Park, Eunseo;Choi, Man-Soo;Kucharski, Daniel;Yi, Yu;Park, Jong-Uk
    • Journal of Astronomy and Space Sciences
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    • v.38 no.1
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    • pp.45-53
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    • 2021
  • GLONASS, a satellite navigation system developed in Russia since 1976, is defunct and orbits in an unstable attitude. The satellites in these problems are not managed and there is no precise information, which can increase the risk of collisions with other space objects. In this study, detailed attitude dynamic have to be analyzed through photometry data, which requires spin period and spin axis. The light curve data is obtained by observing through the photometer at the Graz station and the power spectrum is calculated to obtain the cycle of the satellite. The geometric relationship between observer and sun is analyzed for GLONASS-50 satellite. The box-wing model is applied to obtain the phase reflection of the satellite and obtain the Irradiation of the satellite through this information. In Light Curve and Irradiation, the spin axis is calculated for each peak points with the distance square minimum technique. The spin axis of the GLONASS-50 satellite is RA = 116°, Dec = 92°.

DYNAMIC MODEL DEVELOPMENT FOR INTERPLANETARY NAVIGATION (행성탐사 항행해 결정을 위한 동역학 모델 개발)

  • Park, Eun-Seo;Song, Young-Joo;Yoo, Sung-Moon;Park, Sang-Young;Choi, Kyu-Hong;Yoon, Jae-Cheol;Yim, Jo-Ryeong;Choi, Joon-Min;Kim, Byung-Kyo
    • Journal of Astronomy and Space Sciences
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    • v.22 no.4
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    • pp.463-472
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    • 2005
  • In this paper, the dynamic model development for interplanetary navigation has been discussed. The Cowell method for special perturbation theories was employed to develop an interplanetary trajectory propagator including the perturbations due to geopotential, the Earth's dynamic polar motion, the gravity of the Sun, the Moon and the other planets in the solar system, the relativistic effect of the Sun, solar radiation pressure, and atmospheric drag. The equations of motion in dynamic model were numerically integrated using Adams-Cowell 11th order predictor-corrector method. To compare the influences of each perturbation, trajectory propagation was performed using initial transfer orbit elements of the Mars Express mission launched in 2003, because it can be the criterion to choose proper perturbation models for navigation upon required accuracy. To investigate the performance of dynamic model developed, it was tested whether the spacecraft can reach the Mars. The interplanetary navigation tool developed in this study demonstrated the spacecraft entering the Mars SOI(Sphere of Influence) and its velocity .elative to the Mars was less than the escape velocity of the Mars, hence, the spacecraft can arrive at the target planet. The obtained results were also verified by using the AGI Satellite Tool Kit. It is concluded that the developed program is suitable for supporting interplanetary spacecraft mission for a future Korean Mars mission.

Reconstruction of Remote Sensing Data based on dynamic Characteristics of Time Series Data (위성자료의 시계열 특성에 기반한 실시간 자료 재구축)

  • Jung, Myung-Hee;Lee, Sang-Hoon;Jang, Seok-Woo
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.8
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    • pp.329-335
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    • 2018
  • Satellite images, which are widely used in various applications, are very useful for monitoring the surface of the earth. Since satellite data is obtained from a remote sensor, it contains a lot of noise and errors depending on observation weather conditions during data acquisition and sensor malfunction status. Since the accuracy of the data affects the accuracy and reliability of the data analysis results, noise removal and data restoration for high quality data is important. In this study, we propose a reconstruction system that models the time dependent dynamic characteristics of satellite data using a multi-period harmonic model and performs adaptive data restoration considering the spatial correlation of data. The proposed method is a real-time restoration method and thus can be employed as a preprocessing algorithm for real-time reconstruction of satellite data. The proposed method was evaluated with both simulated data and MODIS NDVI data for six years from 2011 to 2016. Experimental results show that the proposed method has the potentiality for reconstructing high quality satellite data.

RADIOMETRIC CHARACTERISTICS OF KOMPSAT-2 HIGH RESOLUTION IMAGES

  • Chi, Jun-Hwa;Yoon, Jong-Suk;Lee, Kyu-Sung
    • Proceedings of the KSRS Conference
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    • 2007.10a
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    • pp.390-393
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    • 2007
  • KOMPSAT-2, the first Korean high resolution earth observing satellite, continuously acquires high resolution images since July 2006. The quality of satellite images should be geometrically and radiometrically ensured before distribution to users. This study focused on absolute radiometric calibration which is a prerequisite procedure to ensure the radiometric quality of optical satellite images. In this study, we performed reflectance-based vicarious calibration methods on several uniform targets collected through several field campaigns in 2007. The radiative transfer model, MODTRAN, was used to estimate the amount of energy received at the sensor. The energy reached at the sensor are affected by several factors such as reflectance of targets, atmospheric condition, geometry condition between Sun and the sensor, etc. This study proposes the absolute radiometric calibration coefficients of KOMPSAT-2 MSC images combining several types of collected data through field works and tried to compare dynamic range of sensor-detected energy with other commercial high resolution sensors.

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LOS(line-of-sight) Stabilization Control of OTM(on-the-move) Antenna Driven by Geared Flexible Transmission Mechanism (기어와 유연축을 갖는 구동계로 구동되는 OTM 안테나 시선의 안정화 제어)

  • Kang, Min-Sig;Yoon, Wo-Hyun;Lee, Jong-Bee
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.21 no.10
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    • pp.951-959
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    • 2011
  • In this study, an OTM(on-the-move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite while moving was addressed. Since LOS(line-of-sight) of antenna should direct satellite consistently while vehicle moving to guarantee high satellite communication quality, active antenna LOS stabilization is a core technology for OTM antenna. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. In consideration of driving mechanism which consists of gear train and flexible driving shafts, a two-mass-system dynamic model coupled with vehicle motion was presented. An internal PI-control loop + outer PI-control loop structure has been suggested in order to damp the torsional vibration and stabilize control system. The classical pole-placement method was applied to design control gains. In addition, a vehicle motion compensation control beside of the feedback control loop has been suggested to improve LOS stabilization performances. The feasibility of the proposed control design was verified along with some experimental results.