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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 28, Issue 4 - Dec 2011
Volume 28, Issue 3 - Sep 2011
Volume 28, Issue 2 - Jun 2011
Volume 28, Issue 1 - Mar 2011
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WZ Cephei: A Dynamically Active W UMa-Type Binary Star
Jeong, Jang-Hae ; Kim, Chun-Hwey ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 163~172
DOI : 10.5140/JASS.2011.28.3.163
An intensive analysis of 185 timings of WZ Cep, including our new three timings, was made to understand the dynamical picture of this active W UMa-type binary. It was found that the orbital period of the system has complexly varied in two cyclical components superposed on a secularly downward parabola over about 80y. The downward parabola, corresponding to a secular period decrease of
, is most probably produced by the action of both angular momentum loss (AML) due to magnetic braking and mass-transfer from the massive primary component to the secondary. The period decrease rate of
due to AML contributes about 67% to the observed period decrease. The mass flow of about
from the primary to the secondary results the remaining 33% period decrease. Two cyclical components have an
period with amplitude of
period with amplitude of
. It is very interesting that there seems to be exactly in a commensurable 7:2 relation between their mean motions. As the possible causes, two rival interpretations (i.e., light-time effects (LTE) by additional bodies and the Applegate model) were considered. In the LTE interpretation, the minimum masses of
for the shorter period and
for the longer one were calculated. Their contributions to the total light were at most within 2%, if they were assumed to be main-sequence stars. If the LTE explanation is true for the WZ Cep system, the 7:2 relation found between their mean motions would be interpreted as a stable 7:2 orbit resonance produced by a long-term gravitational interaction between two tertiary bodies. In the Applegate model interpretation, the deduced model parameters indicate that the mechanism could work only in the primary star for both of the two period modulations, but could not in the secondary. However, we couldn't find any meaningful relation between the light variation and the period variability from the historical light curve data. At present, we prefer the interpretation of the mechanical perturbation from the third and fourth stars as the possible cause of two cycling period changes.
Mid-latitude Geomagnetic Field Analysis Using BOH Magnetometer: Preliminary Results
Hwang, Jun-Ga ; Choi, Kyu-Cheol ; Lee, Jae-Jin ; Park, Young-Deuk ; Ha, Dong-Hun ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 173~181
DOI : 10.5140/JASS.2011.28.3.173
Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Mt. Bohyun Observatory to measure the Earth's magnetic field variations in South Korea. We, in 2007, installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we provide the preliminary and the first statistical analysis using the BOH magnetometer installed at Mt. Bohyun Observatory. By superposed analysis, we find that daily variations of H, D, and Z shows similar tendency, that is, about 30 minutes before the meridian (11:28) a minimum appears and the time after about 3 hours and 30 minutes (15:28) a maximum appears. Also, a quiet interval start time (19:06) is near the sunset time, and a quiet interval end time (06:40) is near the sunrise time. From the sunset to the sunrise, the value of H has a nearly constant interval, that is, the sun affects the changes in H values. Seasonal variations show similar dependences to the sun. Local time variations show that noon region has the biggest variations and midnight region has the smallest variations. We compare the correlations between geomagnetic variations and activity indices as we expect the geomagnetic variation would contain the effects of geomagnetic activity variations. As a result, the correlation coefficient between H and Dst is the highest (r = 0.947), and other AL, AE, AU index and showed a high correlation. Therefore, the effects of geomagnetic storms and geomagnetic substorms might contribute to the geomagnetic changes significantly.
Analysis of Scaling Parameters of the Batch Unscented Transformation for Precision Orbit Determination using Satellite Laser Ranging Data
Kim, Jae-Hyuk ; Park, Sang-Young ; Kim, Young-Rok ; Park, Eun-Seo ; Jo, Jung-Hyun ; Lim, Hyung-Chul ; Park, Jang-Hyun ; Park, Jong-Uk ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 183~192
DOI : 10.5140/JASS.2011.28.3.183
The current study analyzes the effects of the scaling parameters of the batch unscented transformation on precision satellite orbit determination. Satellite laser ranging (SLR) data are used in the orbit determination algorithm, which consists of dynamics model, observation model and filtering algorithm composed of the batch unscented transformation. TOPEX/Poseidon SLR data are used by utilizing the normal point (NP) data observed from ground station. The filtering algorithm includes a repeated series of processes to determine the appropriate scaling parameters for the batch unscented transformation. To determine appropriate scaling parameters, general ranges of the scaling parameters of
are established. Depending on the range settings, each parameter was assigned to the filtering algorithm at regular intervals. Appropriate scaling parameters are determined for observation data obtained from several observatories, by analyzing the relationship between tuning properties of the scaling parameters and estimated orbit precision. The orbit determination of satellite using the batch unscented transformation can achieve levels of accuracy within several tens of cm with the appropriate scaling parameters. The analyses in the present study give insights into the roles of scaling parameters in the batch unscented transformation method.
Geostationary Orbit Surveillance Using the Unscented Kalman Filter and the Analytical Orbit Model
Roh, Kyoung-Min ; Park, Eun-Seo ; Choi, Byung-Kyu ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 193~201
DOI : 10.5140/JASS.2011.28.3.193
A strategy for geostationary orbit (or geostationary earth orbit [GEO]) surveillance based on optical angular observations is presented in this study. For the dynamic model, precise analytical orbit model developed by Lee et al. (1997) is used to improve computation performance and the unscented Kalman filer (UKF) is applied as a real-time filtering method. The UKF is known to perform well under highly nonlinear conditions such as surveillance in this study. The strategy that combines the analytical orbit propagation model and the UKF is tested for various conditions like different level of initial error and different level of measurement noise. The dependencies on observation interval and number of ground station are also tested. The test results shows that the GEO orbit determination based on the UKF and the analytical orbit model can be applied to GEO orbit tracking and surveillance effectively.
Analysis of Delta-V Losses During Lunar Capture Sequence Using Finite Thrust
Song, Young-Joo ; Park, Sang-Young ; Kim, Hae-Dong ; Lee, Joo-Hee ; Sim, Eun-Sup ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 203~216
DOI : 10.5140/JASS.2011.28.3.203
To prepare for a future Korean lunar orbiter mission, semi-optimal lunar capture orbits using finite thrust are designed and analyzed. Finite burn delta-V losses during lunar capture sequence are also analyzed by comparing those with values derived with impulsive thrusts in previous research. To design a hypothetical lunar capture sequence, two different intermediate capture orbits having orbital periods of about 12 hours and 3.5 hours are assumed, and final mission operation orbit around the Moon is assumed to be 100 km altitude with 90 degree of inclination. For the performance of the on-board thruster, three different performances (150 N with
of 200 seconds, 300 N with
of 250 seconds, 450 N with
of 300 seconds) are assumed, to provide a broad range of estimates of delta-V losses. As expected, it is found that the finite burn-arc sweeps almost symmetric orbital portions with respect to the perilune vector to minimize the delta-Vs required to achieve the final orbit. In addition, a difference of up to about 2% delta-V can occur during the lunar capture sequences with the use of assumed engine configurations, compared to scenarios with impulsive thrust. However, these delta-V losses will differ for every assumed lunar explorer's on-board thrust capability. Therefore, at the early stage of mission planning, careful consideration must be made while estimating mission budgets, particularly if the preliminary mission studies were assumed using impulsive thrust. The results provided in this paper are expected to lead to further progress in the design field of Korea's lunar orbiter mission, particularly the lunar capture sequences using finite thrust.
Development of Precise Point Positioning Method Using Global Positioning System Measurements
Choi, Byung-Kyu ; Back, Jeong-Ho ; Cho, Sung-Ki ; Park, Jong-Uk ; Park, Pil-Ho ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 217~223
DOI : 10.5140/JASS.2011.28.3.217
Precise point positioning (PPP) is increasingly used in several parts such as monitoring of crustal movement and maintaining an international terrestrial reference frame using global positioning system (GPS) measurements. An accuracy of PPP data processing has been increased due to the use of the more precise satellite orbit/clock products. In this study we developed PPP algorithm that utilizes data collected by a GPS receiver. The measurement error modelling including the tropospheric error and the tidal model in data processing was considered to improve the positioning accuracy. The extended Kalman filter has been also employed to estimate the state parameters such as positioning information and float ambiguities. For the verification, we compared our results to other of International GNSS Service analysis center. As a result, the mean errors of the estimated position on the East-West, North-South and Up-Down direction for the five days were 0.9 cm, 0.32 cm, and 1.14 cm in 95% confidence level.
Development of the Earth Observation Camera of MIRIS
Lee, Dae-Hee ; Han, Won-Yong ; Park, Young-Sik ; Park, Sung-Jun ; Moon, Bong-Kon ; Ree, Chang-Hee ; Pyo, Jeong-Hyun ; Jeong, Woong-Seob ; Nam, Uk-Won ; Lee, Duk-Hang ; Park, Kwi-Jong ; Bae, Soo-Ho ; Rhee, Seung-Wu ; Park, Jong-Oh ; Kim, Geon-Hee ; Yang, Sun-Choel ; Kim, Young-Ju ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 225~232
DOI : 10.5140/JASS.2011.28.3.225
We have designed and manufactured the Earth observation camera (EOC) of multi-purpose infrared imaging system (MIRIS). MIRIS is a main payload of the STSAT-3, which will be launched in late 2012. The main objective of the EOC is to test the operation of Korean IR technology in space, so we have designed the optical and mechanical system of the EOC to fit the IR detector system. We have assembled the flight model (FM) of EOC and performed environment tests successfully. The EOC is now ready to be integrated into the satellite system waiting for operation in space, as planned.
Design of Cooling Channels of Preburners for Small Liquid Rocket Engines with Computational Flow and Heat Transfer Analysis
Moon, In-Sang ; Lee, Seon-Mi ; Moon, Il-Yoon ; Yoo, Jae-Han ; Lee, Soo-Yong ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 233~239
DOI : 10.5140/JASS.2011.28.3.233
A series of computational analyses was performed to predict the cooling process by the cooling channel of preburners used for kerosene-liquid oxygen staged combustion cycle rocket engines. As an oxygen-rich combustion occurs in the kerosene fueled preburner, it is of great importance to control the wall temperature so that it does not exceed the critical temperature. However, since the heat transfer is proportional to the speed of fluid running inside the channel, the high heat transfer leads to a trade-off of pressure loss. For this reason, it is necessary to establish a certain criteria between the pressure loss and the heat transfer or the wall surface temperature. The design factors of the cooling channel were determined by the computational research, and a test model was manufactured. The test model was used for the hot fire tests to prove the function of the cooling mechanism, among other purposes.
Development of Distributed Generic Simulator (GenSim) through Invention of Simulated Network (simNetwork)
Koo, Cheol-Hea ; Lee, Hoon-Hee ; Cheon, Yee-Jin ;
Journal of Astronomy and Space Sciences, volume 28, issue 3, 2011, Pages 241~252
DOI : 10.5140/JASS.2011.28.3.241
A simulated network protocol provides the capability of distributed simulation to a generic simulator. Through this, full coverage of management of data and service handling among separated simulators is achieved. The distributed simulation environment is much more conducive to handling simulation load balancing and hazard treatment than a standalone computer. According to the simulated network protocol, one simulator takes on the role of server and the other simulators take on the role of client, and client is controlled by server. The purpose of the simulated network protocol is to seamlessly connect multiple simulator instances into a single simulation environment. This paper presents the development of a simulated network (simNetwork) that provides the capability of distributed simulation to a generic simulator (GenSim), which is a software simulator of satellites that has been developed by the Korea Aerospace Research Institute since 2010, to use as a flight software validation bench for future satellite development.