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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Astronomy and Space Sciences
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The Korean Space Science Society
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Volume & Issues
Volume 26, Issue 4 - Dec 2009
Volume 26, Issue 3 - Sep 2009
Volume 26, Issue 2 - Jun 2009
Volume 26, Issue 1 - Mar 2009
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CCD Photometry of Low Mass Ratio Contact Binary FP Boo - IV
Oh, Kyu-Dong ; Lee, Woo-Baik ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 1~8
DOI : 10.5140/JASS.2009.26.1.001
We present new B, V, and R CCD photometric light curves for the low mass ratio contact binary FP Boo. A new photometric solution and absolute physical dimensions of the system were derived by applying the Wilson-Devinney program to our observed light curves and to previously published Rucinski et al.'s radial velocity curves. From the H-R diagram of 24 low mass ratio contact binary system including FP Boo, the evolutionary stage of FP Boo was found to coincide with those of the general low mass ratio contact binary systems. The light curves obtained in this season show a small asymmetry in their shapes.
Relations Among Sunspots, CMEs and Geomagnetic Storms in Solar Cycle 23
Rho, Su-Lyun ; Chang, Heon-Young ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 9~24
DOI : 10.5140/JASS.2009.26.1.009
We compare the relation among the annual distribution of sunspots: coronal mass ejections (CMEs) and geomagnetic storms and North-South asymmetry during solar cycle 23. For this purpose, we calculate correlation coefficients between (i) annual distribution and N-S asymmetry of CMEs - sunspots (ii) distribution of CMEs - occurrence number of geomagnetic storms (iii) distribution of sunspots - occurrence number of geomagnetic storms. We find that (i) the annual distribution of total CMEs has good correlation with distribution of annual average of sunspots but poor correlation with N-S asymmetry of sunspots, N-S asymmetry of CMEs has good correlation with N-S asymmetry of sunspots: (ii) total and N-S asymmetry of CMEs have poor correlation with occurrence number of geomagnetic storms, it's, however, well correlated with the classified groups of CMEs (Ap, Dst and an indices vs. fast CMEs(
), Dst index vs. Halo CMEs), and (iii) sunspot numbers and area are correlated with occurrence number of geomagnetic storms. We conclude that annual distribution of CMEs and sunspots have well correlated with geomagnetic storms, N-S asymmetry of CMEs and sunspots have poor correlated with the geomagnetic storms.
On the Relation Between the Sun and Climate Change with the Solar North-South Asymmetry
Cho, I.H. ; Kwak, Y.S. ; Cho, K.S. ; Choi, H.S. ; Chang, H.Y. ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 25~30
DOI : 10.5140/JASS.2009.26.1.025
We report the relation between the solar activity and terrestrial climate change with the solar north-south asymmetry. For this purpose, we calculate sliding correlation coefficients between sunspot numbers and earth's mean annual temperature anomalies. Then, we compare the epoch that the sign of correlation changes with the epoch that the sign of the solar north-south asymmetry changes. We obtain that corresponding times are 1907 and 1985, respectively. Further more, these two epoches are well consistent with those of signs of the solar north-south asymmetry changes. We also obtain that the plot between sunspot numbers and temperature anomalies could be classified by 1907 and 1985. We conclude that temperature anomalies are shown to be negatively correlated with sunspot numbers when the southern solar hemisphere is more active: and vice versa.
Unscented KALMAN Filtering for Spacecraft Attitude and Rate Determination Using Magnetometer
Kim, Sung-Woo ; Abdelrahman, Mohammad ; Park, Sang-Young ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 31~46
DOI : 10.5140/JASS.2009.26.1.031
An Unscented Kalman Filter (UKF) for estimation of the attitude and rate of a spacecraft using only magnetometer vector measurement is developed. The attitude dynamics used in the estimation is the nonlinear Euler's rotational equation which is augmented with the quaternion kinematics to construct a process model. The filter is designed for small satellite in low Earth orbit, so the disturbance torques include gravity-gradient torque, magnetic disturbance torque, and aerodynamic drag torque. The magnetometer measurements are simulated based on time-varying position of the spacecraft. The filter has been tested not only in the standby mode but also in the detumbling mode. Two types of actuators have been modeled and applied in the simulation. The PD controller is used for the two types of actuators (reaction wheels and thrusters) to detumble the spacecraft. The estimation error converged to within 5 deg for attitude and 0.1 deg/s for rate respectively when the two types of actuators were used. A joint state parameter estimation has been tested and the effect of the process noise covariance on the parameter estimation has been indicated. Also, Monte-Carlo simulations have been performed to test the capability of the filter to converge with the initial conditions sampled from a uniform distribution. Finally, the UKF performance has been compared to that of the EKF and it demonstrates that UKF slightly outperforms EKF. The developed algorithm can be applied to any type of small satellites that are actuated by magnetic torquers, reaction wheels or thrusters with a capability of magnetometer vector measurements for attitude and rate estimation.
Development of a Hardware-in-the-loop Simulator for Spacecraft Attitude Control Using Thrusters
Koh, Dong-Wook ; Park, Sang-Young ; Kim, Do-Hee ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 47~58
DOI : 10.5140/JASS.2009.26.1.047
In this study, a Hardware-In-the-Loop (HIL) simulator using thrusters is developed to validate the spacecraft attitude system. To control the attitude of the simulator, eight cold gas thrusters are aligned with roll, pitch and yaw axis. Also linear actuators are applied to the HIL simulator for automatic mass balancing to compensate the center of mass offset from the center of rotation. The HIL simulator consists of an embedded computer (Onboard PC) for simulator system control, a wireless adapter for wireless network, a rate gyro sensor to measure 3-axis attitude of the simulator, an inclinometer to measure horizontal attitude, and a battery set to supply power for the simulator independently. For the performance test of the HIL simulator, a bang-bang controller and Pulse-Width Pulse-Frequency (PWPF) modulator are evaluated successfully. The maneuver of 68 deg. in yaw axis is tested for the comparison of the both controllers. The settling time of the bang -bang controller is faster than that of the PWPF modulator by six seconds in the experiment. The required fuel of the PWPF modulator is used as much as 51% of bang-bang controller in the experiment. Overall, the HIL simulator is appropriately developed to validate the control algorithms using thrusters.
Autonomous Real-time Relative Navigation for Formation Flying Satellites
Shim, Sun-Hwa ; Park, Sang-Young ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 59~74
DOI : 10.5140/JASS.2009.26.1.059
Relative navigation system is presented using GPS measurements from a single-channel global positioning system (GPS) simulator. The objective of this study is to provide the real-time inter-satellite relative positions as well as absolute positions for two formation flying satellites in low earth orbit. To improve the navigation performance, the absolute states are estimated using ion-free GRAPHIC (group and phase ionospheric correction) pseudo-ranges and the relative states are determined using double differential carrier-phase data and singled-differential C/A code data based on the extended Kalman filter and the unscented Kalman filter. Furthermore, pseudo-relative dynamic model and modified relative measurement model are developed. This modified EKF method prevents non-linearity of the measurement model from degrading precision by applying linearization about absolute navigation solutions not about the priori estimates. The LAMBDA method also has been used to improve the relative navigation performance by fixing ambiguities to integers for precise relative navigation. The software-based simulation has been performed and the steady state accuracies of 1 m and 6 mm (
of 3-dimensional difference errors) are achieved for the absolute and relative navigation using EKF for a short baseline leader/follower formation. In addition, the navigation performances are compared for the EKF and the UKF for 10 hours simulation, and relative position errors are mm-level for the two filters showing the similar trends.
Performance Comparison of the Batch Filter Based on the Unscented Transformation and Other Batch Filters for Satellite Orbit Determination
Park, Eun-Seo ; Park, Sang-Young ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 75~88
DOI : 10.5140/JASS.2009.26.1.075
The main purpose of the current research is to introduce the alternative algorithm of the non-recursive batch filter based on the unscented transformation in which the linearization process is unnecessary. The presented algorithm is applied to the orbit determination of a low earth orbiting satellite and compared its results with those of the well-known Bayesian batch least squares estimation and the iterative UKF smoother (IUKS). The system dynamic equations consist of the Earth's geo-potential, the atmospheric drag, solar radiation pressure and the lunar/solar gravitational perturbations. The range, azimuth and elevation angles of the satellite measured from ground stations are used for orbit determination. The characteristics of the non recursive unscented batch filter are analyzed for various aspects, including accuracy of the determined orbit, sensitivity to the initial uncertainty, measurement noise and stability performance in a realistic dynamic system and measurement model. As a result, under large non-linear conditions, the presented non-recursive batch filter yields more accurate results than the other batch filters about 5% for initial uncertainty test and 12% for measurement noise test. Moreover, the presented filter exhibits better convergence reliability than the Bayesian least squares. Hence, it is concluded that the non-recursive batch filter based on the unscented transformation is effectively applicable for highly nonlinear batch estimation problems.
Validation of GPS Based Precise Orbits Using SLR Observations
Kim, Young-Rok ; Park, Eun-Seo ; Park, Sang-Young ; Choi, Kyu-Hong ; Hwang, Yoo-La ; Kim, Hae-Yeon ; Lee, Byoung-Sun ; Kim, Jae-Hoon ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 89~98
DOI : 10.5140/JASS.2009.26.1.089
In this study, the YLPODS (Yonsei Laser-ranging Precision Orbit Determination System) is developed for POD using SLR (Satellite Laser Ranging) NP (Normal Point) observations. The performance of YLPODS is tested using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite. JPL's POE (Precision Orbit Ephemeris) is assumed to be true orbit, the measurement residual RMS (Root Mean Square) and the orbit accuracy (radial, along-track, cross-track) are investigated. The validation of POD using GPS (Global Positioning System) raw data is achieved by YLPODS performance and highly accurate SLR NP observations. YGPODS (Yonsei GPS-based Precision Orbit Determination System) is used for generating GPS based precise orbits for TOPEX/POSEIDON. The initial orbit for YLPODS is derived from the YGPODS results. To validate the YGPODS results the range residual of the first adjustment of YLPODS is investigated. The YLPODS results using SLR NP observations of TOPEX/POSEIDON and CHAMP satellite show that the range residual is less than 10 cm and the orbit accuracy is about 1 m level. The validation results of the YGPODS orbits using SLR NP observations of the TOPEX/POSEIDON satellite show that the range residual is less than 10 cm. This result predicts that the accuracy of this GPS based orbits is about 1m level and it is compared with JPL's POE. Thus this result presents that the YLPODS can be used for POD validation using SLR NP observations such as STSAT-2 and KOMPSAT-5.
A Preliminary Development of Real-Time Hardware-in-the-Loop Simulation Testbed for the Satellite Formation Flying Navigation and Orbit Control
Park, Jae-Ik ; Park, Han-Earl ; Shim, Sun-Hwa ; Park, Sang-Young ; Choi, Kyu-Hong ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 99~110
DOI : 10.5140/JASS.2009.26.1.099
The main purpose of the current research is to developments a real-time Hardware In-the-Loop (HIL) simulation testbed for the satellite formation flying navigation and orbit control. The HIL simulation testbed is integrated for demonstrations and evaluations of navigation and orbit control algorithms. The HIL simulation testbed is composed of Environment computer, GPS simulator, Flight computer and Visualization computer system. GPS measurements are generated by a SPIRENT GSS6560 multi-channel RF simulator to produce pseudorange, carrier phase measurements. The measurement date are transferred to Satrec Intiative space borne GPS receiver and exchanged by the flight computer system and subsequently processed in a navigation filter to generate relative or absolute state estimates. These results are fed into control algorithm to generate orbit controls required to maintain the formation. These maneuvers are informed to environment computer system to build a close simulation loop. In this paper, the overall design of the HIL simulation testbed for the satellite formation flying navigation and control is presented. Each component of the testbed is then described. Finally, a LEO formation navigation and control simulation is demonstrated by using virtual scenario.
Orbit Determination Using Angle-Only Data for MEO & GEO Satellite and Obsolete
Choi, Jin ; Kim, Bang-Yeop ; Yim, Hong-Suh ; Chang, Heon-Young ; Yoon, Joh-Na ; Kim, Myung-Jin ; Hwang, Ok-Jun ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 111~126
DOI : 10.5140/JASS.2009.26.1.111
We used an optical observation system with a 0.6m wide-field telescope and 5 computers system in KASI (Korean Astronomy and Space Science Institute) for satellite optical observation. Optical data have errors that are caused by targeting, expose start time and end-point determination. Gauss method for initial orbit determination was tested using angle-only data simulated by KODAS. And suitable time span is confirmed for result which has minimum errors. Initial orbit determination results are proved that optical observation system in KASI is possible satellite tracking for a short period. And also through differential correction, initial orbit determination results are improved.
Development of COMS DATS C&M S/W
Kim, Su-Jin ; Park, Durk-Jong ; Koo, In-Hoi ; Ahn, Sang-Il ;
Journal of Astronomy and Space Sciences, volume 26, issue 1, 2009, Pages 127~140
DOI : 10.5140/JASS.2009.26.1.127
COMS DATS C&M software is an integrated management system providing control and monitoring functionalities for COMS IDACS (Image Data Acquisition and Control System). DATS C&M S/W consists of a system management module, a control and monitoring module, a data management module, and a trend analysis module. COMS SOC is supposed to operate IDACS as a backup of MSC. Especially, for the backup operation, the control and monitoring module of DATS C&M S/W is designed to support the synchronization of the two IDACS systems. This paper describes design, implementation, and result of development of DATS C&M S/W.