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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 20, Issue 4 - Dec 2003
Volume 20, Issue 3 - Sep 2003
Volume 20, Issue 2 - Jun 2003
Volume 20, Issue 1 - Mar 2003
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TRIFLE DIFFERENCE APPROACH TO LOW EARTH ORBITER PRECISION ORBIT DETERMINATION
Kwon, Jay-Hyoun ; Grejner brzezinska, Dorota-A. ; Yom, Jae-Hong ; Lee, Dong-Cheon ;
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 1~10
DOI : 10.5140/JASS.2003.20.1.001
A precise kinematic orbit determination (P-KOD) procedure for Low Earth Orbiter(LEO) using the GPS ion-free triple differenced carrier phases is presented. Because the triple differenced observables provide only relative information, the first epoch`s positions of the orbit should be held fixed. Then, both forward and backward filtering was executed to mitigate the effect of biases of the first epoch`s position. p-KOD utilizes the precise GPS orbits and ground stations data from International GPS Service (IGS) so that the only unknown parameters to be solved are positions of the satellite at each epoch. Currently, the 3-D accuracy off-KOD applied to CHAMP (CHAllenging Min-isatellite Payload) shows better than 35 cm compared to the published rapid scientific orbit (RSO) solution from GFZ (GeoForschungsZentrum Potsdam). The data screening for cycle slips is a particularly challenging procedure for LEO, which moves very fast in the middle of the ionospheric layer. It was found that data screening using SNR (signal to noise ratio) generates best results based on the residual analysis using RSO. It is expected that much better accuracy are achievable with refined prescreening procedure and optimized geometry of the satellites and ground stations.
ESTIMATION OF THE SGP4 DRAG TERM FROM TWO OSCULATING ORBIT STATES
Lee, Byoung-Sun ; Park, Jae-Woo ;
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 11~20
DOI : 10.5140/JASS.2003.20.1.011
A method for estimating the NORAD SGP4 atmospheric drag term from minimum osculating orbit states, i.e., two osculating orbits, is developed. The first osculating orbit state is converted into the NORAD TLE-type mean orbit state by iterative procedure. Then the converted TLE is propagated to the second orbit state using the SGP4 model with the incremental SGP4 drag term. The iterative orbit propagation procedure is finished when the difference of the two osculating semi-major axes between the propagated orbit and the given second orbit is minimized. In order to minimize the effect of the short-term variations of the osculating semi-major axis, the osculating argument of latitude of the second orbit is propagated to the same argument of latitude of the first orbit. The method is applied to the estimation of the NORAD-type TLE for the KOMPSAT-1 spacecraft. The SGP4 drag terms are estimated from both NORAD SGP4 orbit propagation and the numerical orbit propagation results. Variations of the estimated drag terms are analyzed for the KOMPSAT-1 satellite orbit determination results.
REAL - TIME ORBIT DETERMINATION OF LOW EARTH ORBIT SATELLITES USING RADAR SYSTEM AND SGP4 MODEL
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 21~28
DOI : 10.5140/JASS.2003.20.1.021
In case that we independently obtain orbital informations about the low earth satellites of foreign countries using radar systems, we develop the orbit determination algorithm for this purpose using a SGP4 model with an analytical orbit model and the extended Kalman filter with a real-time processing method. When the state vector is Keplerian orbital elements, singularity problems happen to compute partial derivative with respect to inclination and eccentricity orbit elements. To cope with this problem, we set state vector osculating to mean equinox and true equator cartesian elements with coordinate transformation. The state transition matrix and the covariance matrix are numerically computed using a SGP4 model. Observational measurements are the type of azimuth, elevation and range, filter process to each measurement in a lump. After analyzing performance of the developed orbit determination algorithm using TOPEX/POSEIDON POE(precision 0.bit Ephemeris), its position error has about 1 km. To be similar to performance of NORAD system that has up to 3km position accuracy during 7 days need to radar system performance that have accuracy within 0.1 degree for azimuth and elevation and 50m for range.
ACQUISITION OF THE FLIGHT INFORMATION USING THE KSR-3 MAGNETOMETER
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 29~42
DOI : 10.5140/JASS.2003.20.1.029
The KSR-3 magnetometers consist of the fluxgate magnetometer (MAG/AIM) for acquiring the rocket flight attitude information, and the search-coil magnetometer (MAG/SIM) for the observation of the Earth`s magnetic fluctuations. The position (latitude, longitude, and height) and flight condition (the transformation angle) of the rocket is measured after the data based on these two magnetometers are compared with IGRF The gap in the vector of magnetic field between the position of the launching point and an impact point is taken into account in data reduction. Angular variation of pitch, yaw, and roll can be researched when the data is applied to the coordinate system of the rocket.
RELATIONSHIP BETWEEN RELATIVISTIC ELECTRON EVENTS, MAGNETIC STORMS, AND MAGNETIC SUBSTORMS
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 43~52
DOI : 10.5140/JASS.2003.20.1.043
This paper reports a statistical study on the relationship between relativistic electron events(REE), magnetic storms, and substorms. We have used magnetic storm events that occurred between 1996 and 1998, and have classified them into two groups, (i) magnetic storms with REE and (ii) magnetic storms without REE, according to whether or not the magnetic storm is accompanied by REE. Then we have examined the characteristics of substorms that occurred during the main phase of each of the magnetic storms, and compared them between the two groups of the storms. In particular, we have made some quantitative estimations on the intensities of the energetic particle injections and magnetic dipolarizations during the substorm. We find that the injection intensity ratio and the magnetic dipolaization of the storm-time substorms are bigger for substorms with REE than for those without REE.
PRELIMINARY STUDY ON THE ABRUPT DENSITY ENHANCEMENT IN LOW LATITUDE REGION DETECTED BY KOMPSAT-I
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 53~62
DOI : 10.5140/JASS.2003.20.1.053
SPS(Space Physics Sensor) onboard the KOMPSAT-I, which was launched at 1999, had transmitted ionospheric plasma density and electron temperature during the solar maximum from June 2000 to August 2001, SPS IMS onboard KOMPSAT-I occasionally detected abrupt plasma density enhancement in low-latitude region, in which the plasma density abruptly increases in a narrow region. Statistical analysis of the data obtained during the entire operational period shows that the occurrence probability of these events has its peak value at the Atlantic region and at the Hawaiian region where the geomagnetic field strength is weak. And the occurrence frequency has no correlation with Dst index or F10.7 index. The correlation between plasma density and the electron temperature shows a wide variety, but the anti-correlated cases are dominant.
DYNAMICAL MODELS OF SPHERICAL GALAXIES WITH MASSIVE HALO
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 63~82
DOI : 10.5140/JASS.2003.20.1.063
Using the Schwarzschild`s linear programming technique, we obtained the general solutions of the collisionless Bolzmann equation describing the spherical galaxy in dynamical equilibrium. From this calculation we have confirmed the existence of isotropic spherical galaxies obeying a de Vaucouleurs`law which includes a dark halo. The flattening profile of the velocity dispersion curve seen in the elliptical galaxies can be explained as the increase of mass to light ratio in this dark matter. The space density distribution of this dark matter shows that the core radius of the dark matter is smaller than the effective radius of the galaxy.
A STUDY OF SASIN-ANIMAL SKY MAP ON CHONMUNRYUCHO
Journal of Astronomy and Space Sciences, volume 20, issue 1, 2003, Pages 83~94
DOI : 10.5140/JASS.2003.20.1.083
Chon-Mun-Ryu-Cho (天文類抄), written (edited) by Lee Sun-Ji (李純之) during the period of King Se-Jong, is a representative astronomy book of Cho-Sun (朝鮮: A.D. 1392-1910) Dynasty. We find and study in the first page of the book; the description of 28 oriental constellations as a Sasin (four mythical oriental animals)-animal sky map which is not widely known yet. The map consists of four groups of constellations, each of which represents the Sasin: Chang-Ryong (蒼龍: dragon), Baek-Ho (白虎: tige.s with Ki-Rin [離隣: Oriental giraffe]), Ju-Jak (朱崔: Chinese phoenix), Hyun-Mu (玄武: a tortoise interwined with a snake). Each group (animals) spans 2 ～ 7 of 28 oriental constellations (宿). As we know from the illustration (論說) of the Chon-Sang-Yol-Cha-Bun-Ya-Ji-Do (天象列次分野之圖), a representative sky map of Cho-Sun Dynasty, astronomy in Cho-Sun Dynasty is closely related to that in Go- Gu-Rye. (高句麗: B.C. 37 -A.D. 668) Dynasty. Since these Sasin-animals appear in most mural paintings of Go-Gu-Rye. (高句麗) tombs, visualization of sky with these animal constellations could have been established as early as in Go-Gu-Ryer Dynasty. We also reconstruct this ”A Sasin-animal Korean sky map” based on the shapes of the Sasin and Ki-Rin from Go-Gu-Ryer paintings and 28 oriental constellations in Chon- S an g- Yol- C h a- B un- Ya- J i- Do.