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한국우주과학회지

1984년 ~ 2024년까지 1,231 건한국우주과학회지를 계간으로 확인하실 수 있습니다.

  • The Korean Space Science Society (The Korean Astronomical Society)
  • 계간 (Quarterly)
  • ISSN : 1225-052x (ISSN : 1225-052x)
  • DB구축현황 : 1,231건 (DB Construction : 1,231 Articles)
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총 게시글 1,231 페이지 3/124
21
The Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, successfully entered its mission orbit on December 27, 2022 (UTC), and is currently performing its mission smoothly. To mitigate potential contingencies during the flight and to navigate the spacecraft into the desired lunar orbit, the KPLO flight dynamics (FD) team analyzed major trajectory-related contingencies that could lead to the violation of mission requirements and prepared operational procedures from the perspective of trajectory and FD. This paper presents the process of preparing contingency trajectory operations for the KPLO, including the identification of trajectory contingencies, prioritization results, and the development of recovery plans and operational procedures. The prepared plans were successfully applied to address minor contingencies encountered during actual operations. The results of this study will provide valuable insights to FD engineers preparing for space exploration mission operations.
22
Korea Polar Research Institute (KOPRI) and Korea Astronomy and Space Institute (KASI) have been participating in the European Incoherent Scatter (EISCAT) Scientific Association as an affiliate institution in order to observe the polar ionosphere since 2015. During the period of December 16-21, 2016 and January 3-9, 2018, the observations for the polar ionospheric parameters such as the electron density profiles, ion drift, and electron/ion temperature are carried out in the polar cap/cusp region by the EISCAT Svalbard radar (ESR). The purpose of the observations is to investigate the characteristic of the winter ionosphere in the dayside polar cap/cusp region. In this paper, we briefly report the results of the ESR observations for winter daytime ionosphere and also the simultaneous observations for the ionosphere-thermosphere system together with the balloon-borne instrument High-Altitude Interferometer WIND Experiment (HIWIND) performed by the High Altitude Observatory (HAO), National Center for Atmospheric Research (NCAR). We further introduce our research activities using long-term EISCAT observations for the occurrence of ion upflow and the climatology of the polar ionospheric density profiles in comparison with the mid-latitude ionosphere. Finally, our future research plans will briefly be introduced.
23
  • Mohammad Sh. Odeh
  • Journal of astronomy and space sciences
  • 40, n.1
  • pp.19-27
  • 2023
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We present the results of using small telescopes in the United Arab Emirates (UAE) for observing variable stars and asteroids. Two telescopes, namely, 5' apochromatic refractor and 14' Schmidt-Cassegrain, at Al-Khatim Observatory (M44) were used for the observations. The targets were the three variable stars RR GEM, AG LMi, and DL CMi and the asteroid 22 Kalliope. We found a good consistency between our light curves and published ones for the calibration targets, i.e., the asteroid 22 Kalliope and the variable star RR GEM. According to previous studies, AG LMi has two suggested periods, 16.3 hours and 32.62 hours. Our results clearly confirm the second one, with a period of 32.6175 hours. The star DL CMi has several suggested periods as per previous studies, such as 4.0173 days, 1.9606 days, and 2.0086 days. Our observations confirm the first one, with a period of 4.0159 days. These results demonstrate the effectiveness of using small telescopes for observing variable stars and asteroids. This work provides some recommendations on using small telescopes for such observations.
25
  • Hongsu Kim
  • Journal of astronomy and space sciences
  • 40, n.4
  • pp.247-258
  • 2023
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Studying the accretion phenomena provides a window into understanding most heavenly bodies, from the birth of stars to active galactic nuclei (AGN). We would adopt the effect of the radiation pressure, which reduces accretion rates (Ṁ), on the accretion phenomena. The Shakura-Sunyaev α-disk model of disk accretion is a good candidate theory of advection dominated accretion flow (ADAF). Reduction in the angular velocity leads to the suppression the disk luminosity and surface temperature, essentially indicating the transition of the standard accretion disk model from convection dominated accretion flow (CDAF) to ADAF.
26
  • Alexander Yushchenko
  • Journal of astronomy and space sciences
  • 40, n.1
  • pp.29-33
  • 2023
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An unexplained acceleration on the order of 10<sup>-8</sup> cm s<sup>-2</sup>, which is close to cH, where c is the speed of light and H is the Hubble constant, is detected in gravitationally bound systems of different scales, from the solar system to clusters of galaxies. We found that any test body located inside a fractal structure with fractal dimension D = 2 experiences acceleration of the same order and confirmed the previous work that photons propagating through this structure decrease the frequency owing to gravitational redshift. The acceleration can be directed against the movement of the test body. The fractal distribution of the matter should be at scales of at least hundreds of megaparsecs to a few gigaparsecs for the existence of this acceleration.
27
  • Dongwoo Kim
  • Journal of astronomy and space sciences
  • 40, n.1
  • pp.35-44
  • 2023
  • 원문 바로보기
Surveillance and reconnaissance intelligence in the space domain will become increasingly important in future battlefield environments. Moreover, to assimilate the military provocations and trends of hostile countries, imagery intelligence of the highest possible resolution is required. There are many methods for improving the resolution of optical satellites when observing the ground, such as designing satellite optical systems with a larger diameter and lowering the operating altitude. In this paper, we propose a method for improving ground observation resolution by using an optical system for a previously designed low orbit satellite and lowering the operating altitude of the satellite. When the altitude of a satellite is reduced in a circular orbit, a large amount of thrust fuel is required to maintain altitude because the satellite's altitude can decrease rapidly due to atmospheric drag. However, by using the critical inclination, which can fix the position of the perigee in an elliptical orbit to the observation area, the operating altitude of the satellite can be reduced using less fuel compared to a circular orbit. This method makes it possible to obtain a similar observational resolution of a medium-sized satellite with the same weight and volume as a small satellite. In addition, this method has the advantage of reducing development and launch costs to that of a small-sized satellite. As a result, we designed an elliptical orbit. The perigee of the orbit is 300 km, the apogee is 8,366.52 km, and the critical inclination is 116.56&#x00B0;. This orbit remains at its lowest altitude to the Korean peninsula constantly with much less orbit maintenance fuel compared to the 300 km circular orbit.
28
  • Mark Southwick Robinson
  • Journal of astronomy and space sciences
  • 40, n.4
  • pp.149-171
  • 2023
  • 원문 바로보기
ShadowCam is a National Aeronautics and Space Administration Advanced Exploration Systems funded instrument hosted onboard the Korea Aerospace Research Institute (KARI) Korea Pathfinder Lunar Orbiter (KPLO) satellite. By collecting high-resolution images of permanently shadowed regions (PSRs), ShadowCam will provide critical information about the distribution and accessibility of water ice and other volatiles at spatial scales (1.7 m/pixel) required to mitigate risks and maximize the results of future exploration activities. The PSRs never see direct sunlight and are illuminated only by light reflected from nearby topographic highs. Since secondary illumination is very dim, ShadowCam was designed to be over 200 times more sensitive than previous imagers like the Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC). ShadowCam images thus allow for unprecedented views into the shadows, but saturate while imaging sunlit terrain.
29
  • Hee-Bok Ahn
  • Journal of astronomy and space sciences
  • 40, n.2
  • pp.59-66
  • 2023
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Since the World Health Organization (WHO) officially announced a global pandemic on March 12, 2020, the aviation industry in the world has been experiencing difficulties for a long time. Meanwhile, the Ukraine war broke out in February, and from March 15, domestic airlines must operate air routes bypassing Russian airspace despite the longer flight time. Therefore, as the flight time increases, the cosmic radiation exposure dose of the crew members is also expected to increase. Here we compare the radiation exposure dose between the route doses for the eastern United States and Europe before and after the detour route usage. Through the comparison analysis, we tried to understand how cosmic radiation changes depending on the flight time and the latitude and which one contributes more. We expect that this study can be used for the policy update for the safety management of cosmic radiation for aircrews in Korea.
30
  • Iyida, Evaristus U.
  • Journal of astronomy and space sciences
  • 39, n.2
  • pp.43-50
  • 2022
  • 원문 바로보기
The unified scheme of Seyfert galaxies hypothesizes that the observed differences between the two categories of Seyfert galaxies, type 1 (Sy1) and type 2 (Sy2) are merely due to the difference in the orientation of the toroidal shape of the obscuring material in the active galactic nuclei. We used in this paper, a sample consisting of 120 Seyfert galaxies at 1.40 &#x00D7; 10<sup>9</sup> Hz in radio, 2.52 &#x00D7; 10<sup>17</sup> Hz in X-ray and 2.52 &#x00D7; 10<sup>23</sup> Hz in &#x03B3;-ray luminosities observed by the Fermi Large Area Telescope (Fermi-LAT) in order to test the unified scheme of radio-quiet Seyfert galaxies. Our main results are as follows: (i) We found that the distributions of multiwave luminosities (L<sub>radio</sub>, L<sub>X-ray</sub>, and L<sub>&#x03B3;-ray</sub>) of Sy1 and Sy2 are completely overlapped with up to a factor of 4. The principal component analysis result reveals that Sy1 and Sy2 also occupy the same parameter spaces, which agrees with the notion that Sy1 and Sy2 are the same class objects. A Kolmogorov-Smirnov test performed on the sub-samples indicates that the null hypothesis (both are from the same population) cannot be rejected with chance probability p ~ 0 and separation distance K = 0.013. This result supports the fact that there is no statistical difference between the properties of Sy1 and Sy2 (ii) We found that the coefficient of the best-fit linear regression equation between the common properties of Sy1 and Sy2 is significant (r > 0.50) which plausibly implies that Sy1 and Sy2 are the same type of objects observed at different viewing angle.