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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 19, Issue 4 - Dec 2002
Volume 19, Issue 3 - Sep 2002
Volume 19, Issue 2 - Jun 2002
Volume 19, Issue 1 - Mar 2002
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ESTIMATION OF A GENERAL ALONG-TRACK ACCELERATION IN THE KOMPSAT-1 ORBIT
Lee, Byoung-Sun ; Lee, Jeong-Sook ; Kim, Jae-Hoon ;
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 89~96
DOI : 10.5140/JASS.2002.19.2.089
General along-track acceleration was estimated in the KOMPSAT-1 orbit determination process. Several sets of the atmospheric drag and solar radiation pressure coefficients were also derived with the different spacecraft area. State vectors in the orbit determination with the different spacecraft area were compared in the time frame. The orbit prediction using the estimated coefficients was performed and compared with the orbit determination results. The orbit prediction with the different general acceleration values was also carried out for the comparison
DESIGN AND FLIGHT SOFTWARE EMBEDDING OF KOMPSAT-2 SIMULATOR
Lee, Sang-Uk ; Cho, Sung-Ki ; Kim, Jae-Hoon ;
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 97~106
DOI : 10.5140/JASS.2002.19.2.097
The design feature of KOMPSAT-2 simulator based on object oriented design methodology in terms of unified modeling language (UML) has been discussed in this paper. Also, we present how to embed flight software into the simulator. Flight software em-bedding for KOMPSAT-2 simulator is compared to that of the KOMPSAT-1 simulator.
ATTITUDE AND CONFIGURATION CONTROL OF FLEXIBLE MULTI-BODY SPACECRAFT
Choi, Sung-Ki ; Jone, E. ; Cochran, Jr. ;
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 107~122
DOI : 10.5140/JASS.2002.19.2.107
Multi-body spacecraft attitude and configuration control formulations based on the use of collaborative control theory are considered. The control formulations are based on two-player, nonzero-sum, differential game theory applied using a Nash strategy. It is desired that the control laws allow different components of the multi-body system to perform different tasks. For example, it may be desired that one body points toward a fixed star while another body in the system slews to track another satellite. Although similar to the linear quadratic regulator formulation, the collaborative control formulation contains a number of additional design parameters because the problem is formulated as two control problems coupled together. The use of the freedom of the partitioning of the total problem into two coupled control problems and the selection of the elements of the cross-coupling matrices are specific problems ad-dressed in this paper. Examples are used to show that significant improvement in performance, as measured by realistic criteria, of collaborative control over conventional linear quadratic regulator control can be achieved by using proposed design guidelines.
LONGITUDINAL AND SEASONAL VARIATIONS OF THE ELECTRON TEMPERATURE AND DENSITY IN THE LOW_LATITUDE TOPSIDE IONOSPHERE OBSERVED BY KOMPSAT-1
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 123~132
DOI : 10.5140/JASS.2002.19.2.123
The electron density and temperature in the topside ionosphere are observed by the ionosphere Measurement Sensor (IMS) onboard the KOMPSAT-1, which has the sun-synchronous orbit of the altitude of 685 km and the orbital inclination of
with a descending node at 22:50LT. Observations have been analyzed to determine the seasonal variations of the electron density and temperature in the low-latitude region. Only the night-time (22:50LT) behavior on magnetically quiet days (Kp < 4) has been examined. Observations show a strong longitudinal and seasonal variation. Generally, in the dip equator the density increases and the temperature decreases. In equinox the latitudinal distributions of the electron density and temperature are quite symmetric about the dip equator. However, the local maximum of the density and the local minimum of the temperature shift toward the Northern hemisphere in summer solstice but the Southern hemisphere in winter solstice. Such variations are due to the influences of field-aligned plasma transport induced by F region neutral wind. Compared with the IRI95 model, the observed electron density and temperature show significant differences from those predicted by the IRI95 model.
STUDY ON EQUATORIAL, BUBBLES DETECTED BY SPS IMS ONBOARD THE KOMPSAT-I
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 133~140
DOI : 10.5140/JASS.2002.19.2.133
Space Physics Sensor onboard the KOMPSAT-1, which was launched at 1999, had transmitted ionospheric data during the solar maximum from June 2000 to August 2001. When the KOMPSAT-1 has passed the equatorial region, equatorial bubbles, in which the electron density abruptly decreases, had frequently been detected. Statistical analysis of the data obtained during the entire operational period shows equatorial bubbles frequently occur across the Atlantic region where the geomagnetic field strength is weak. Also, equatorial bubbles occur more frequently for lower Kp index. The results are in good agreement with the previous observations by DMSP satellites and radio experiments at the Peruvian sector The correlation between electron density and the electron temperature shows various behaviors from event to event.
ESTIMATION OF IONOSPHERIC CONDUCTIVITY BASED ON THE MEASUREMENTS BY SUPERDARN HF RADARS AND GREENLAND MAGNETOMETERS
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 141~150
DOI : 10.5140/JASS.2002.19.2.141
The ionosphere plays an important role in the electrodynamics of space environment. In particular, the information on the ionospheric conductivity distribution is indispensable in understanding the electrodynamics of the magnetosphere and ionosphere coupling study. To meet such a requirement, several attempts have been made to estimate the conductivity distribution over the polar ionosphere. As one of such attempts we compare the ionospheric plasma convection patterns obtained from the Super Dual Auroral Radar Network (SuperDARN), from which the electric field distribution is estimated, and the simultaneously measured ground magnetic disturbance. Specifically, the electric field measured from the Goose Bay and Stokkseyri radars and magnetic disturbance data obtained from the west coast chain of Greenland are compared. In order to estimate ionospheric conductivity distribution with these information, the overhead infinite sheet current approximation is employed. As expected, the Hall conductance, height-integrated conductivity, shows a wide enhancement along the center of the auroral electrojet. However, Pedersen conductance shows negative values over a wide portion of the auroral oval region, a physically unacceptable situation. To alleviate this problem, the effect of the field-aligned current is taken into account. As a result, the region with negative Pedersen conductance disappears significantly, suggesting that the effect of the field-aligned current should be taken into account, when one wants to estimate ionospheric conductance based on ground magnetic disturbance and electric field measurements by radars.
COMPARISON OF APPROXIMATE MODELS FOR HIGH ENERGY COSMIC RADIATION SHIELDING CALCULATION
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 151~162
DOI : 10.5140/JASS.2002.19.2.151
Two approximate calculation models for a cosmic radiation shielding in satellite are compared with detailed 3-dimensional calculation results. One is a sectoring method and the other is a chord-length distribution method. Shielding caltulation is performed for KITSAT-1 under the assumed environment at SAA (South Atlantic Anomaly) location with AP-8 radiation spectrum model. When both approximate models are applied, calculation error is expected compared with 3-D detailed geometry calculation because of straight knock-on assumption neglecting the deflection of incident proton. However, both approximate models showed good agreements with 3-dimensional detailed Monte Carlo calculation in two dose detector locations.
PREPROCESSING OF THE GPS RAW DATA FOR THE PRECISION ORBIT DETERMINATION BY DGPS TECHNIQUE
Journal of Astronomy and Space Sciences, volume 19, issue 2, 2002, Pages 163~172
DOI : 10.5140/JASS.2002.19.2.163
This article investigates the problem of data preprocessing for the precision orbit determination (POD) of low earth orbit satellite using GPS .aw data. Several data preprocessing algorithms have been developed to edit the GPS data automatically such that outlier deletion, cycle slip identification and correction, and time tag error correction. The GPS data are precisely edited for the accuracy of POD. Some methods of data preprocessing are restricted to the rate of the collections of the pseudorange and carrier phase measurements. This study considers the preprocessing efficiency varied with the rate, the quality of receiver and the altitude of the satellite's orbit. We also propose the proper methods in accordance with the rate for single frequency and dual frequency receivers.