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1984년 ~ 2025년까지 1,253 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 : 1,253건 (DB Construction : 1,253 Articles)
총 게시글 1,253건
페이지 36/126
351
- Cheng, Kwong Sang
- Journal of astronomy and space sciences
- 30, n.3
- pp.153-158
- 2013
- 원문 바로보기
In this review paper we explain the following gamma-ray emission features from the millisecond pulsars. (1) Why is the dipolar field of millisecond pulsars so weak but the magnetic pair creation process may still be able to control the size of the outergap? (2) A sub-GeV pulse component could occur in the vicinity of the radio pulse of millisecond pulsars. (3) Orbital modulated gamma-rays should exist in the black widow systems for large viewing angle.
352
- Lee, Yong Sam
- Journal of astronomy and space sciences
- 30, n.3
- pp.187-192
- 2013
- 원문 바로보기
Honsangui (celestial globe) which is a water-hammering method astronomical clock is recorded in 'Juhaesuyong' which is Volume VI of supplement from 'Damheonseo', written by Hong Dae-Yong (1731~1783). We made out the conceptual design of Hong Dae-Yong's Honsangui through the study on its structure and working mechanism. Honsangui consist of three rings and two layers, the structure of rings which correspond to outer layer is similar to his own Tongcheonui (armillary sphere) which is a kind of armillary sphere. Honsang sphere which correspond to inner layer depicts constellations and milky way and two beads hang on it as Sun and Moon respectively for realize the celestial motion. Tongcheonui is operated by the pendulum power but Honsangui is operated by water-hammering method mechanism. This Honsangui's working mechanism is the traditional way of Joseon and it was simplified the working mechanism of Shui y<TEX>$\ddot{u}$</TEX>n i hsiang t'ai which is a representative astronomical clock of China. This record of Honsangui is the only historical record about the water-hammering method working mechanism of Joseon Era and it provide the study of water-hammering method mechanism with a vital clue.
353
- Yun, Jongyeon
- Journal of astronomy and space sciences
- 30, n.4
- pp.223-230
- 2013
- 원문 바로보기
Sudden enhancements of daytime NmF2 appeared in Anyang ionosonde data during summer seasons in 2006-2007. In order to investigate the causes of this unusual enhancement, we compared Anyang NmF2's with the total electron contents (GPS TECs) observed at Daejeon, and also with ionosonde data at at mid-latitude stations. First, we found no similar increase in Daejeon GPS TEC when the sudden enhancements of Anyang NmF2 occurred. Second, we investigated NmF2's observed at other ionosonde stations that use the same ionosonde model and auto-scaling program as the Anyang ionosonde. We found similar enhancements of NmF2 at these ionosonde stations. Moreover, the analysis of ionograms from Athens and Rome showed that there were sporadic-E layers with high electron density during the enhancements in NmF2. The auto-scaling program (ARTIST 4.5) used seems to recognize sporadic-E layer echoes as a F2 layer trace, resulting in the erroneous critical frequency of F2 layer (foF2). Other versions of the ARTIST scaling program also seem to produce similar erroneous results. Therefore we conclude that the sudden enhancements of NmF2 in Anyang data were due to the misrecognition of sporadic-E echoes as a F-layer by the auto-scaling program. We also noticed that although the scaling program flagged confidence level (C-level) of an ionogram as uncertain when a sporadic-E layer occurs, it still automatically computed erroneous foF2's. Therefore one should check the confidence level before using long term ionosonde data that were produced by an auto-scaling program.
354
Performance Analysis of Generating Function Approach for Optimal Reconfiguration of Formation Flying
- Lee, Kwangwon
- Journal of astronomy and space sciences
- 30, n.1
- pp.17-24
- 2013
- 원문 바로보기
The use of generating functions for solving optimal rendezvous problems has an advantage in the sense that it does not require one to guess and iterate the initial costate. This paper presents how to apply generating functions to analyze spacecraft optimal reconfiguration between projected circular orbits. The series-based solution obtained by using generating functions demonstrates excellent convergence and approximation to the nonlinear reference solution obtained from a numerical shooting method. These favorable properties are expected to hold for analyzing optimal formation reconfiguration under perturbations and non-circular reference orbits.
355
- Chang, Heon-Young
- Journal of astronomy and space sciences
- 30, n.3
- pp.163-168
- 2013
- 원문 바로보기
Parameters associated with solar minimum have been studied to relate them to solar activity at solar maximum so that one could possibly predict behaviors of an upcoming solar cycle. The number of active days has been known as a reliable indicator of solar activity around solar minimum. Active days are days with sunspots reported on the solar disk. In this work, we have explored the relationship between the sunspot numbers at solar maximum and the characteristics of the monthly number of active days. Specifically, we have statistically examined how the maximum monthly sunspot number of a given solar cycle is correlated with the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days for the corresponding solar cycle. We have calculated the linear correlation coefficient r and the Spearman rank-order correlation coefficient <TEX>$r_s$</TEX> for data sets prepared under various conditions. Even though marginal correlations are found, they turn out to be insufficiently significant (r ~ 0.3). Nonetheless, we have confirmed that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is less steep when solar cycles belonging to the 'Modern Maximum' are considered compared with rests of solar cycles. We conclude, therefore, that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is indeed dependent on the solar activity at its maxima, but that this simple relationship should be insufficient as a valid method to predict the following solar activity amplitude.
356
- Wang, Yu
- Journal of astronomy and space sciences
- 30, n.2
- pp.91-94
- 2013
- 원문 바로보기
We use the outer gap model to explain the spectrum and the energy dependent light curves of the X-ray and soft <TEX>${\gamma}$</TEX>-ray radiations of the spin-down powered pulsar PSR B1509-58. In the outer gap model, most pairs inside the gap are created around the null charge surface and the gap's electric field separates the opposite charges to move in opposite directions. Consequently, the region from the null charge surface to the light cylinder is dominated by the outflow current and that from the null charge surface to the star is dominated by the inflow current. We suggest that the viewing angle of PSR B1509-58 only receives the inflow radiation. The incoming curvature photons are converted to pairs by the strong magnetic field of the star. The X-rays and soft <TEX>${\gamma}$</TEX>-rays of PSR B1509-58 result from the synchrotron radiation of these pairs. The magnetic pair creation requires a large pitch angle, which makes the pulse profile of the synchrotron radiation distinct from that of the curvature radiation. We carefully trace the pulse profiles of the synchrotron radiation with different pitch angles. We find that the differences between the light curves of different energy bands are due to the different pitch angles of the secondary pairs, and the second peak appearing at E > 10 MeV comes from the region near the star, where the stronger magnetic field allows the pair creation to happen with a smaller pitch angle.
357
- Yen, Tzu-Ching
- Journal of astronomy and space sciences
- 30, n.3
- pp.159-162
- 2013
- 원문 바로보기
We report the detection of a quasi-sinusoidally modulated optical flux with a period of 4.6343 hour in the optical and infrared band of the Fermi source 2FGL J2339.7-0531. Comparing the multi-wavelength observations, we suggest that 2FGL J2339.7- 0531 is a <TEX>${\gamma}$</TEX>-ray emitting millisecond pulsar (MSP) in a binary system with an optically visible late-type companion accreted by the pulsar, where the MSP is responsible for the <TEX>${\gamma}$</TEX>-ray emission while the optical and infrared emission originate from the heated side of the companion. Based on the optical properties, the companion star is believed to be heated by the pulsar and reaches peak magnitude when the heated side faces the observer. We conclude that 2FGL J2339.7-0531 is a member of a subclass of <TEX>${\gamma}$</TEX>-ray emitting pulsars -the 'black widows'- recently revealed to be evaporating their companions in the late-stage of recycling as a prominent group of these newly revealed Fermi sources.
358
- Lim, Seong-Min
- Journal of astronomy and space sciences
- 30, n.4
- pp.279-290
- 2013
- 원문 바로보기
Due to the continuous space development by mankind, the number of space objects including space debris in orbits around the Earth has increased, and accordingly, difficulties of space development and activities are expected in the near future. In this study, among the stages for space debris removal, the implementation of a vision-based approach technique for approaching space debris from a far-range rendezvous state to a proximity state, and the ground test performance results were described. For the vision-based object tracking, the CAM-shift algorithm with high speed and strong performance, and the Kalman filter were combined and utilized. For measuring the distance to a tracking object, a stereo camera was used. For the construction of a low-cost space environment simulation test bed, a sun simulator was used, and in the case of the platform for approaching, a two-dimensional mobile robot was used. The tracking status was examined while changing the position of the sun simulator, and the results indicated that the CAM-shift showed a tracking rate of about 87% and the relative distance could be measured down to 0.9 m. In addition, considerations for future space environment simulation tests were proposed.
359
- Kim, Young-Rok
- Journal of astronomy and space sciences
- 30, n.4
- pp.269-277
- 2013
- 원문 바로보기
In this study, we present results of precise orbital geodetic parameter estimation using satellite laser ranging (SLR) observations for the International Laser Ranging Service (ILRS) associate analysis center (AAC). Using normal point observations of LAGEOS-1, LAGEOS-2, ETALON-1, and ETALON-2 in SLR consolidated laser ranging data format, the NASA/GSFC GEODYN II and SOLVE software programs were utilized for precise orbit determination (POD) and finding solutions of a terrestrial reference frame (TRF) and Earth orientation parameters (EOPs). For POD, a weekly-based orbit determination strategy was employed to process SLR observations taken from 20 weeks in 2013. For solutions of TRF and EOPs, loosely constrained scheme was used to integrate POD results of four geodetic SLR satellites. The coordinates of 11 ILRS core sites were determined and daily polar motion and polar motion rates were estimated. The root mean square (RMS) value of post-fit residuals was used for orbit quality assessment, and both the stability of TRF and the precision of EOPs by external comparison were analyzed for verification of our solutions. Results of post-fit residuals show that the RMS of the orbits of LAGEOS-1 and LAGEOS-2 are 1.20 and 1.12 cm, and those of ETALON-1 and ETALON-2 are 1.02 and 1.11 cm, respectively. The stability analysis of TRF shows that the mean value of 3D stability of the coordinates of 11 ILRS core sites is 7.0 mm. An external comparison, with respect to International Earth rotation and Reference systems Service (IERS) 08 C04 results, shows that standard deviations of polar motion <TEX>$X_P$</TEX> and <TEX>$Y_P$</TEX> are 0.754 milliarcseconds (mas) and 0.576 mas, respectively. Our results of precise orbital and geodetic parameter estimation are reasonable and help advance research at ILRS AAC.
360
- Choi, Byung-Kyu
- Journal of astronomy and space sciences
- 30, n.3
- pp.207-212
- 2013
- 원문 바로보기
Ionosphere is one of the largest error sources when the navigational signals produced by Global Positioning System (GPS) satellites are transmitted. Therefore it is very important to estimate total electron contents (TEC) in ionosphere precisely for navigation, precise positioning and some other applications. When we provide ionospheric TEC values in real-time, its application can be expanded to other areas. In this study we have used data obtained from nine Global Navigation Satellite System (GNSS) reference stations which have been operated by Korea Astronomy and Space Science Institute (KASI) to detect ionospheric TEC over South Korea in real-time. We performed data processing that covers converting 1Hz raw data delivered from GNSS reference stations to Receiver INdependent Exchange (RINEX) format files at intervals of 5 minutes. We also analyzed the elevation angles of GPS satellites, vertical TEC (VTEC) values and their changes.