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1984년 ~ 2024년까지 1,246 건의 한국우주과학회지를 계간으로 확인하실 수 있습니다.
- The Korean Space Science Society (The Korean Astronomical Society)
- 계간 (Quarterly)
- ISSN : 1225-052x (ISSN : 1225-052x)
1225-052x
- DB구축현황 : 1,246건 (DB Construction : 1,246 Articles)
총 게시글 1,246건
페이지 10/125
91
- Park, Kyung Sun
- Journal of astronomy and space sciences
- 37, n.2
- pp.77-84
- 2020
- 원문 바로보기
We performed high-resolution three-dimensional global magnetohydrodynamic (MHD) simulations to study the interaction between the Earth's magnetosphere and a prolonged steady southward interplanetary magnetic field (IMF) (Bz = -2nT) and slow solar wind. The simulation results show that dayside magnetic reconnection continuously occurs at the subsolar region where the magnetosheath magnetic field is antiparallel to the geomagnetic field. The plasmoid developed on closed plasma sheet field lines. We found that the vortex was generated at the magnetic equator such as (X, Y) = (7.6, 8.9) R<sub>E</sub> due to the viscous-like interaction, which was strengthened by dayside reconnection. The magnetic field and plasma properties clearly showed quasiperiodic variations with a period of 8-10 min across the vortex. Additionally, double twin parallel vorticity in the polar region was clearly seen. The peak value of the cross-polar cap potential fluctuated between 17 and 20 kV during the tail reconnection.
92
- Song, Min-Sup
- Journal of astronomy and space sciences
- 37, n.3
- pp.199-208
- 2020
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This paper presents a kinematic ephemeris generator for Korea Pathfinder Lunar Orbiter (KPLO) and its performance test results. The kinematic ephemeris generator consists of a ground ephemeris compressor and an onboard ephemeris calculator. The ground ephemeris compressor has to compress desired orbit propagation data by using an interpolation method in a ground system. The onboard ephemeris calculator can generate spacecraft ephemeris and the Sun/Moon ephemeris in onboard computer of the KPLO. Among many interpolation methods, polynomial interpolation with uniform node, Chebyshev interpolation, Hermite interpolation are tested for their performances. As a result of the test, it is shown that all the methods have some cases that meet requirements but there are some performance differences. It is also confirmed that, the Chebyshev interpolation shows better performance than other methods for spacecraft ephemeris generation, and the polynomial interpolation with uniform nodes yields good performance for the Sun/Moon ephemeris generation. Based on these results, a Kinematic ephemeris generator is developed for the KPLO mission. Then, the developed ephemeris generator can find an approximating function using interpolation method considering the size and accuracy of the data to be transmitted.
93
- Kim, Young-Rok
- Journal of astronomy and space sciences
- 37, n.4
- pp.237-247
- 2020
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The ground tracking support is a critical factor for the navigation performance of spacecraft orbiting around the Moon. Because of the tracking limit of antennas, only a small number of facilities can support lunar missions. Therefore, case studies for various ground tracking support conditions are needed for lunar missions on the stage of preliminary mission analysis. This study analyzes the ground supporting condition effect on orbit determination (OD) of Korea Pathfinder Lunar Orbiter (KPLO) in the lunar orbit. For the assumption of ground support conditions, daily tracking frequency, cut-off angle for low elevation, tracking measurement accuracy, and tracking failure situations were considered. Two antennas of deep space network (DSN) and Korea Deep Space Antenna (KDSA) are utilized for various tracking conditions configuration. For the investigation of the daily tracking frequency effect, three cases (full support, DSN 4 pass/day and KDSA 4 pass/day, and DSN 2 pass/day and KDSA 2 pass/day) are prepared. For the elevation cut-off angle effect, two situations, which are 5 deg and 10 deg, are assumed. Three cases (0%, 30%, and 50% of degradation) were considered for the tracking measurement accuracy effect. Three cases such as no missing, 1-day KDSA missing, and 2-day KDSA missing are assumed for tracking failure effect. For OD, a sequential estimation algorithm was used, and for the OD performance evaluation, position uncertainty, position differences between true and estimated orbits, and orbit overlap precision according to various ground supporting conditions were investigated. Orbit prediction accuracy variations due to ground tracking conditions were also demonstrated. This study provides a guideline for selecting ground tracking support levels and preparing a backup plan for the KPLO lunar mission phase.
94
- Choi, Cheong Rim
- Journal of astronomy and space sciences
- 37, n.1
- pp.35-42
- 2020
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Particle-in-cell simulations were performed to understand the interaction of the solar wind with localized magnetic fields on the sunlit surface of the Moon. The results indicated a mini-magnetosphere was formed which had a thin magnetopause with the thickness of the electron skin depth. It was also found that the solar wind penetrated into the cavity of the magnetosphere intermittently rather than in a steady manner. The solar wind that moved around the magnetosphere was observed to hit the surface of the Moon, implying that it may be the cause of the lunar swirl formation on the surface.
95
- Park, Sa-Rah
- Journal of astronomy and space sciences
- 37, n.1
- pp.43-50
- 2020
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We have developed an algorithm for tracking coronal mass ejection (CME) propagation that allows us to estimate CME speed and its arrival time at Earth. The algorithm may be used either to forecast the CME's arrival on the day of the forecast or to update the CME tracking information for the next day's forecast. In our case study, we successfully tracked CME propagation using the algorithm based on g-values of interplanetary scintillation (IPS) observation provided by the Institute for Space-Earth Environmental Research (ISEE). We were able to forecast the arrival time (Δt = 0.30 h) and speed (Δv = 20 km/s) of a CME event on October 2, 2000. From the CME-interplanetary CME (ICME) pairs provided by Cane & Richardson (2003), we selected 50 events to evaluate the algorithm's forecast capability. Average errors for arrival time and speed were 11.14 h and 310 km/s, respectively. Results demonstrated that g-values obtained continuously from any single station observation were able to be used as a proxy for CME speed. Therefore, our algorithm may give stable daily forecasts of CME position and speed during propagation in the region of 0.2-1 AU using the IPS g-values, even if IPS velocity observations are insufficient. We expect that this algorithm may be widely accepted for use in space weather forecasting in the near future.
96
- Khattab, Elamira Hend
- Journal of astronomy and space sciences
- 37, n.1
- pp.1-9
- 2020
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Frozen orbit is an attractive option for orbital design owing to its characteristics (its argument of pericenter and eccentricity are kept constant on an average). Solar sails are attractive solutions for massive and expensive missions. However, the solar radiation pressure effect represents an additional force on the solar sail that may greatly affect its orbital behavior in the long run. Thus, this force must be included as a perturbation force in the dynamical model for more accuracy. This study shows the calculations of initial conditions for a lunar solar sail frozen orbit. The disturbing function of the problem was developed to include the lunar gravitational field that is characterized by uneven mass distribution, third body perturbation, and the effect of solar radiation. An averaging technique was used to reduce the dynamical problem to a long period system. Lagrange planetary equations were utilized to formulate the rate of change of the argument of pericenter and eccentricity. Using the reduced system, frozen orbits for the Moon sail orbiter were constructed. The resulting frozen orbits are shown by two 3Dsurface (semi-major, eccentricity, inclination) figures. To simplify the analysis, we showed inclination-eccentricity contours for different values of semi-major axis, argument of pericenter, and values of sail lightness number.
97
- Kang, Seokju
- Journal of astronomy and space sciences
- 37, n.1
- pp.51-60
- 2020
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This study designs and analyzes satellite formation flying concepts for the Small scale magNetospheric and Ionospheric Plasma Experiments (SNIPE) mission, that will observe the near-Earth space environment using four nanosats. To meet the requirements to achieve the scientific objectives of the SNIPE mission, three formation flying concepts are analyzed: a cross-shape formation, a square-shape formation, and a cross-track formation. Of the three formation flying scenarios, the cross-track formation scenario is selected as the final scenario for the SNIPE mission. The result of this study suggests a relative orbit control scenario for formation maintenance and reconfiguration, and the initial relative orbits of the four nanosats meeting the formation requirements and thrust limitations of the SNIPE mission. The formation flying scenario is validated by calculating the accumulated total thrust required for the four nanosats. If the cross-track formation scenario presented in this study is applied to the SNIPE mission, it is expected that the mission will be successfully accomplished.
98
- Jeong, Miri
- Journal of astronomy and space sciences
- 37, n.3
- pp.187-197
- 2020
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In order to avoid the high cost and high risk of demonstration mission of rendezvous-docking technology, missions using nanosatellites have recently been increasing. However, there are few successful mission cases due to many limitations of nanosatellites like small size, power limitation, and limited performances of sensor, thruster, and controller. To improve the probability of rendezvous-docking mission success using nanosatellite, a rendezvous-docking phase analysis tool for nanosatellites is developed. The tool serves to analyze the relative position and attitude control of the chaser satellite at the docking phase. In this tool, the Model Predictive Controller (MPC) is implemented as a controller, and Extended Kalman Filter (EKF) is adopted as a filter for noise filtering. To verify the performance and effectiveness of the developed tool for nanosatellites, simulation study was conducted. Consequently, we confirmed that this tool can be used for the analysis of relative position and attitude control for nanosatellites in the rendezvous-docking phase.
99
- Kim, Jiwoo
- Journal of astronomy and space sciences
- 37, n.1
- pp.19-27
- 2020
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Pc1 pulsations are important to consider for the interpretation of wave-particle interactions in the Earth's magnetosphere. In fact, the wave properties of these pulsations change dynamically when they propagate from the source region in the space to the ground. A detailed study of the wave features can help understanding their time evolution mechanisms. In this study, we statistically analyzed Pc1 pulsations observed by a Bohyunsan (BOH) magneto-impedance (MI) sensor located in Korea (L = 1.3) for ~one solar cycle (November 2009-August 2018). In particular, we investigated the temporal occurrence ratio of Pc1 pulsations (considering seasonal, diurnal, and annual variations in the solar cycle), their wave properties (e.g., duration, peak frequency, and bandwidth), and their relationship with geomagnetic activities by considering the Kp and Dst indices in correspondence of the Pc1 pulsation events. We found that the Pc1 waves frequently occurred in March in the dawn (1-3 magnetic local time (MLT)) sector, during the declining phase of the solar cycle. They generally continued for 2-5 minutes, reaching a peak frequency of ~0.9 Hz. Finally, most of the pulsations have strong dependence on the geomagnetic storm and observed during the early recovery phase of the geomagnetic storm.
100
- Jeong, Jaesik
- Journal of astronomy and space sciences
- 37, n.3
- pp.165-170
- 2020
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Muons and neutrons are representative secondary particles that are generated by interactions between primary cosmic ray particles (mostly protons) and the nuclei of atmospheric gas compounds. Previous studies reported that muons experience seasonal variations because of the meteorological effects of temperature. The intensity of neutrons has a typical modulation with various periods and reasons, such as diurnal and solar variation or transient events. This paper reports that cosmic ray particles, which were observed by neutron monitors, have seasonal variations using the daily data at the Oulu neutron monitor. To eliminate the effects of solar activity across time, the daily data were normalized by two different transformations: transformations with respect to the grand mean and yearly mean. The data after transformation with respect to the yearly mean showed more statistical stability and clear seasonal variations. On the other hand, it is difficult to determine if the seasonal variation results from terrestrial effects, such as meteorological factors, or extraterrestrial effects, such as the position of the Earth in its orbit of revolution.