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1984년 ~ 2026년까지 1,258 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 : 1,258건 (DB Construction : 1,258 Articles)
총 게시글 1,258건
페이지 34/126
331
- Jeong, Meeyoung
- Journal of astronomy and space sciences
- 31, n.4
- pp.317-323
- 2014
- 원문 바로보기
Odyssey, one of the NASA's Mars exploration program and SELENE (Kaguya), a Japanese lunar orbiting spacecraft have a payload of Gamma-Ray Spectrometer (GRS) for analyzing radioactive chemical elements of the atmosphere and the surface. In these days, gamma-ray spectroscopy with a High-Purity Germanium (HPGe) detector has been widely used for the activity measurements of natural radionuclides contained in the soil of the Earth. The energy spectra obtained by the HPGe detectors have been generally analyzed by means of the Window Analysis (WA) method. In this method, activity concentrations are determined by using the net counts of energy window around individual peaks. Meanwhile, an alternative method, the so-called Full Spectrum Analysis (FSA) method uses count numbers not only from full-absorption peaks but from the contributions of Compton scattering due to gamma-rays. Consequently, while it takes a substantial time to obtain a statistically significant result in the WA method, the FSA method requires a much shorter time to reach the same level of the statistical significance. This study shows the validation results of FSA method. We have compared the concentration of radioactivity of <TEX>$^{40}K$</TEX>, <TEX>$^{232}Th$</TEX> and <TEX>$^{238}U$</TEX> in the soil measured by the WA method and the FSA method, respectively. The gamma-ray spectrum of reference materials (RGU and RGTh, KCl) and soil samples were measured by the 120% HPGe detector with cosmic muon veto detector. According to the comparison result of activity concentrations between the FSA and the WA, we could conclude that FSA method is validated against the WA method. This study implies that the FSA method can be used in a harsh measurement environment, such as the gamma-ray measurement in the Moon, in which the level of statistical significance is usually required in a much shorter data acquisition time than the WA method.
332
- Hong, Ik-Seon
- Journal of astronomy and space sciences
- 31, n.2
- pp.131-140
- 2014
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Lava caves could be useful as outposts for the human exploration of the Moon. Lava caves or lava tubes are formed when the external surface of the lava flows cools more quickly to make a hardened crust over subsurface lava flows. The lava flow eventually ceases and drains out of the tube, leaving an empty space. The frail part of the ceiling of lava tube could collapse to expose the entrance to the lava tubes which is called a pit crater. Several pit craters with the diameter of around 100 meters have been found by analyzing the data of SELENE and LRO lunar missions. It is hard to use these pit craters for outposts since these are too large in scale. In this study, small scale pit craters which are fit for outposts have been investigated using the NAC image data of LROC. Several topographic patterns which are believed to be lunar caves have been found and the similar pit craters of the Earth were compared and analyzed to identify caves. For this analysis, the image data of satellites and aerial photographs are collected and classified to construct a database. Several pit craters analogous to lunar pit craters were derived and a morphological pit crater model was generated using the 3D printer based on this database.
333
- Hui, Chung-Yue
- Journal of astronomy and space sciences
- 31, n.2
- pp.101-120
- 2014
- 원문 바로보기
The nature of the exotic stellar corpses which reincarnate by consuming their companion is reviewed. Apart from sucking life from their partners, they are actually eating the doomed companions away by their deadly and powerful particle/radiation beams. Such situation resembles that a female 'black widow' spider that eats its mate after mating. These celestial zombies are called - Millisecond pulsars (MSPs). In this review article, I will focus on the effort of Fermi Asian Network (FAN) in exploring these intricating objects over the last five years. Two special classes of MSPs are particularly striking. Since Fermi Gamma-ray Space Telescope has started surveying the gamma-ray sky, the population of 'black widows' has been boosted. Another dramatic class is so-called 'redbacks' (Australian cousin of 'black widows') which has just emerged in the last few years. These MSPs provide us with a long-sought missing link in understanding the transition between accretion-powered and rotation-powered systems. The strategy of hunting MSPs through mulitwavelength observations of the unidentified Fermi objects is also reviewed.
334
- Kim, Young-Soo
- Journal of astronomy and space sciences
- 31, n.4
- pp.341-346
- 2014
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A prototype of the GMT FSM has been developed to acquire and to enhance the key technology - mirror fabrication and tip-tilt actuation. The ellipsoidal off-axis mirror has been designed, analyzed, and fabricated from light-weighting to grinding, polishing, and figuring of the mirror surface. The mirror was tested by using an interferometer together with CGHs, which revealed the surface error of 13.7 nm rms in the diameter of 1030 mm. The SCOTS test was employed to independently validate the test results. It measured the surface error to be 17.4 nm rms in the diameter of 1010 mm. Both tests show the optical surface of the FSMP mirror within the required value of 20 nm rms surface error.
335
- Kim, Jung-Hee
- Journal of astronomy and space sciences
- 31, n.1
- pp.7-13
- 2014
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Variabilities in the solar wind cause disturbances throughout the heliosphere on all temporal and spatial scales, which leads to changeable space weather. As a view of space weather forecasting, in particular, it is important to know direct and indirect causes modulating the space environment near the Earth in advance. Recently, there are discussions on a role of the interaction of the solar wind with Mercury in affecting the solar wind velocity in the Earth's neighborhood during its inferior conjunctions. In this study we investigate a question of whether other parameters describing the space environment near the Earth are modulated by the inner planets' wake, by examining whether the interplanetary magnetic field and the proton density in the solar wind observed by the Advanced Composition Explorer (ACE) spacecraft, and the geomagnetic field via the Dst index and Auroral Electrojet index (AE index) are dependent upon the relative position of the inner planets. We find there are indeed apparent variations. For example, the mean variations of the geomagnetic fields measured in the Earth's neighborhood apparently have varied with a timescale of about 10 to 25 days. Those variations in the parameters we have studied, however, turn out to be a part of random fluctuations and have nothing to do with the relative position of inner planets. Moreover, it is found that variations of the proton density in the solar wind, the Dst index, and the AE index are distributed with the Gaussian distribution. Finally, we point out that some of properties in the behavior of the random fluctuation are to be studied.
336
- Lee, Ki-Won
- Journal of astronomy and space sciences
- 31, n.1
- pp.63-66
- 2014
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Since Rigollet first discovered a comet in 1939, many follow-up observations have been made, particularly in Europe. It is now known that the Rigollet comet is identical with the one observed by Herschel in 1788, and thus it is now called 35P/1939 O1 or the Herschel-Rigollet comet. Yumi, a Japanese astronomer, also observed the Rigollet comet in Korea using a 6-inch refractor telescope, and published his data in two Japanese journals (Bulletin of the Observatory of the Government-General of Korea and Publication of the Lecture on Meteorology). In his paper, Yumi also referred to observations by Hirose and Kanda in Japan. However, their works have not been given attention by international society. In this study, we analyze the observation data of Yumi and present preliminary orbital elements using it with a modified Gauss method. We expect that this study will be used to refine the orbital elements of the Rigollet comet by orbital-calculation experts. For that reason, we have also transcribed all the observational data presented by Yumi.
337
- Jung, Jongil
- Journal of astronomy and space sciences
- 31, n.2
- pp.141-144
- 2014
- 원문 바로보기
Recently, cave candidates have been discovered on other planets besides the Earth, such as the Moon and Mars. When we go to other planets, caves could be possible human habitats providing natural protection from cosmic threats. In this study, seven cave candidates have been found on Pavonis Mons and Ascraeus Mons in Tharsis Montes on Mars. The cave candidates were selected using the images of the Context Camera (CTX) on the Mars Reconnaissance Orbiter (MRO). The Context Camera could provide images with the high resolution of 6 meter per pixel. The diameter of the candidates ranges from 50 to 100m. Cushing et al. (2007) have analyzed the temperature change at daytime and nighttime using the Thermal Emission Imaging System (THEMIS) for the sites of potential cave candidates. Similarly, we have examined the temperature change at daytime and at nighttime for seven cave candidates using the method of Cushing et al. (2007). Among those, only one candidate showed a distinct temperature change. However, we cannot verify a cave based on the temperature change only and further study is required for the improvement of this method to identify caves more clearly.
338
- Oh, Jae Sok
- Journal of astronomy and space sciences
- 31, n.2
- pp.177-186
- 2014
- 원문 바로보기
The Immersion Grating Infrared Spectrometer (IGRINS) is a near-infrared wide-band high-resolution spectrograph jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS employs three HAWAII-2RG Focal Plane Array (H2RG FPA) detectors. We present the design and fabrication of the detector mount for the H2RG detector. The detector mount consists of a detector housing, an ASIC housing, a Field Flattener Lens (FFL) mount, and a support base frame. The detector and the ASIC housing should be kept at 65 K and the support base frame at 130 K. Therefore they are thermally isolated by the support made of GFRP material. The detector mount is designed so that it has features of fine adjusting the position of the detector surface in the optical axis and of fine adjusting yaw and pitch angles in order to utilize as an optical system alignment compensator. We optimized the structural stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis. Based on the structural and thermal analysis, the designed detector mount meets an optical stability tolerance and system thermal requirements. Actual detector mount fabricated based on the design has been installed into the IGRINS cryostat and successfully passed a vacuum test and a cold test.
339
- Kim, Jung-Hee
- Journal of astronomy and space sciences
- 31, n.2
- pp.159-167
- 2014
- 원문 바로보기
Solar variability is widely known to affect the interplanetary space and in turn the Earth's electromagnetical environment on the basis of common periodicities in the solar and geomagnetic activity indices. The goal of this study is twofold. Firstly, we attempt to associate modes by comparing a temporal behavior of the power of geomagnetic activity parameters since it is barely sufficient searching for common peaks with a similar periodicity in order to causally correlate geomagnetic activity parameters. As a result of the wavelet transform analysis we are able to obtain information on the temporal behavior of the power in the velocity of the solar wind, the number density of protons in the solar wind, the AE index, the Dst index, the interplanetary magnetic field, B and its three components of the GSM coordinate system, <TEX>$B_X$</TEX>, <TEX>$B_Y$</TEX>, <TEX>$B_Z$</TEX>. Secondly, we also attempt to search for any signatures of influence on the space environment near the Earth by inner planets orbiting around the Sun. Our main findings are as follows: (1) Parameters we have investigated show periodicities of ~ 27 days, ~ 13.5 days, ~ 9 days. (2) The peaks in the power spectrum of <TEX>$B_Z$</TEX> appear to be split due to an unknown agent. (3) For some modes powers are not present all the time and intervals showing high powers do not always coincide. (4) Noticeable peaks do not emerge at those frequencies corresponding to the synodic and/or sidereal periods of Mercury and Venus, which leads us to conclude that the Earth's space environment is not subject to the shadow of the inner planets as suggested earlier.
340
- Shin, Dae-Kyu
- Journal of astronomy and space sciences
- 31, n.4
- pp.303-309
- 2014
- 원문 바로보기
The Earth's outer radiation belt often suffers from drastic changes in the electron fluxes. Since the electrons can be a potential threat to satellites, efforts have long been made to model and predict electron flux variations. In this paper, we describe a prediction model for the outer belt electrons that we have recently developed at Chungbuk National University. The model is based on a one-dimensional radial diffusion equation with observationally determined specifications of a few major ingredients in the following way. First, the boundary condition of the outer edge of the outer belt is specified by empirical functions that we determine using the THEMIS satellite observations of energetic electrons near the boundary. Second, the plasmapause locations are specified by empirical functions that we determine using the electron density data of THEMIS. Third, the model incorporates the local acceleration effect by chorus waves into the one-dimensional radial diffusion equation. We determine this chorus acceleration effect by first obtaining an empirical formula of chorus intensity as a function of drift shell parameter <TEX>$L^*$</TEX>, incorporating it as a source term in the one-dimensional diffusion equation, and lastly calibrating the term to best agree with observations of a certain interval. We present a comparison of the model run results with and without the chorus acceleration effect, demonstrating that the chorus effect has been incorporated into the model to a reasonable degree.