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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 1/126
1
- Kim, Jung-Hee
- Journal of astronomy and space sciences
- 43, n.1
- pp.27-34
- 2026
- 원문 바로보기
<P> Here, we have statistically investigated the averaged occurrence rate of sunspots during active days to test whether it is uniform across solar cycles, motivated by an intriguing observation that weak solar cycles tend to be preceded by solar minimum with numerous spotless days. The occurrence rate of sunspot in a particular month is defined by a ratio of the monthly sunspot number to the number of active days in the corresponding month. The cycle with a large number of spotless days becomes weak owing to either a small number of active days during solar cycle or a lower occurrence rate per day during active days of solar cycle, or even both. More specifically speaking, we have attempted to examine whether the averaged occurrence rate of sunspots during weak solar cycles differs from that of strong ones, and, if so, determine in what part of solar cycle the occurrence rate contributes to such changes in sunspot number. As a result, we find that the occurrence rate of sunspot averaged over the period from maximum of (i − 1)-th solar cycle to maximum of i-th solar cycle is negatively correlated with the number of spotless days, and is correlated with sunspot numbers. It is found that the averaged occurrence rate appears to more significantly correlate with the sunspot number when the sun is relatively more active compared to the period when the sun is relatively less active. It is also found that the averaged occurrence rate of sunspot does not correlate with length of solar cycle, nor length of ascending phase. Finally, we conclude by pointing out implications of our findings. </P>
2
- Brown, Holly M.
- Journal of astronomy and space sciences
- 43, n.1
- pp.1-19
- 2026
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<P> Lunar slopes have distinct patterned regolith textures, but their formation mechanism remains enigmatic. We mapped the distribution of these “elephant hide” texture (EHT) occurrences in and out of shadow near the south pole (90°S to 88°S) at a scale of 1:25,000 and 1:20,000 to test if permanently shadowed regions (PSRs) have unique regolith properties relative to non-shadowed areas (polar and equatorial). We recorded the presence or absence of EHT occurrences in grid-map cells (5 and 1 km2) using Lunar Reconnaissance Orbiter Narrow Angle Camera images of illuminated terrain, and Korea Pathfinder Lunar Orbiter ShadowCam images of permanently and temporarily shadowed terrain. We find that diffuse lighting does not interfere with the ability to identify textures. We observed that EHT has a similar likelihood to occur on shallow slopes ≤ 5° in both illuminated and permanently shadowed terrain, with no difference in texture morphology across temperature boundaries or from PSR to PSR. This suggests that regolith properties in PSRs that are relevant to EHT formation are not significantly different from those of the illuminated surface. We also observed variations of EHT across the same slopes and EHT on near-horizontal surfaces (≤ 3°) within ~500 m of the foot of slopes. This suggests that patterned regolith textures are formed by down-slope transport of loose regolith, likely driven by both episodic and continuous disturbances. </P>
3
- Han, Seung Ho
- Journal of astronomy and space sciences
- 43, n.1
- pp.21-26
- 2026
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<P> Polishing is a critical process in fabricating space-telescope mirrors because it determines the surface figure and consequently optical performance. Deterministic polishing relies on the tool influence function (TIF), which describes the spatial material-removal profile. At nanometric removal depths, the TIF becomes highly sensitive to process conditions, limiting the accuracy of analytic models such as Preston’s equation. In this study, we propose a deep learning-based approach to predict TIF depth for polishing a Silicon Carbide (SiC) mirror surface. To mitigate data scarcity, we augment 231 experimental measurements with Gaussian noise consistent with the repeatability observed in repeated trials (≈ 20 nm peak-to-peak). The resulting model achieves a validation mean absolute error (MAE) of 4.24 nm and a test MAE of 3.99 nm; on nine additional experimental cases, the MAE is 6.75 nm. These results indicate that the proposed augmentation improves robustness to experimental variability and supports the development of a data-driven, automated polishing workflow. </P>
4
- Prasun Mahanti
- Journal of astronomy and space sciences
- 42, n.4
- pp.85-96
- 2025
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The Shackleton crater permanently shadowed region (PSR) exhibits high 1,064 nm reflectance and S-band radar circular polarization ratios (CPR), which previous studies interpreted as indicating the presence of water-ice or frost. In the absence of photogeologic evidence, alternative hypotheses offered for the reflective properties of the Shackleton crater PSR (mass wasting, presence of pure anorthosite, and interior blockiness) were not confirmed. ShadowCam has acquired high signal-to-noise ratio stereo images of Shackleton crater; we use these images, derived digital terrain models, and M<sup>3</sup> data to show that episodic mass wasting is active inside Shackleton, arising from the instability of steep wall slopes. We conclude that the relatively high reflectance within the Shackleton PSR results from continued exposure of plagioclase-rich material and not from water-ice or frost. In addition, mass wasting also excavates small blocks that collect on the wall and floor, mainly responsible for the enhanced radar CPR signature.
5
- Myunghwan Kim
- Journal of astronomy and space sciences
- 42, n.1
- pp.29-37
- 2025
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This study examined the variations of solar, interplanetary, and geomagnetic (SIG) parameters from 1974 to 2024 to assess the changes in the solar cycle. Eleven SIG parameters were analyzed, including the sunspot number (SSN), solar magnetic field, 10.7 cm solar radio flux, total solar irradiance, and Ap index. This study also aimed to predict Solar Cycle 25 using the seasonal autoregressive integrated moving average (SARIMA) statistical forecasting model. The results showed that consistent with previous studies, all SIG parameters exhibited a strong correlation with the SSN. The change in SSN strongly influences the variations in all SIG parameters, even though some exhibit time-lagged responses. The cross-correlation analysis revealed a high correlation coefficient of 0.9678 between the SSN and the 10.7 cm solar radio flux without delay. Most SIG parameters showed a general weakening trend toward Solar Cycles 22-24. This suggests that solar activity is waning over time. In particular, the solar polar magnetic field (SPMF) showed a large decrease in the solar minimum 23/24, and specifically, the SPMF at the south pole weakened more rapidly than at the north pole. Hence, the SPMF is changing asymmetrically between the north and south poles. This weakening of the solar magnetic field suggests an increase in galactic cosmic rays within the heliosphere, exposing the Earth to higher levels of cosmic rays. Finally, forecasts for Solar Cycle 25 using the SARIMA model predict that the SSN will continue to decline after the solar maximum in 2024, with the predicted minimum SSN of 9.42 in October 2028, and will likely enter a solar minimum period around 2030.
6
- Junho Back
- Journal of astronomy and space sciences
- 42, n.2
- pp.39-46
- 2025
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The electron density profiles produced from the ionospheric sounding system are traditionally estimated by the inversion procedure based on the image analysis of the observed ionograms. Jang Bogo Vertical Incidence Pulsed Ionospheric Radar (VIPIR) with Dynasonde (hereafter, JVD), however, uses the three-dimensional electron density inversion approach named 'NeXtYZ' to produce ionospheric density, ion velocity, and tilt of the ionization in the bottomside ionosphere based on the list of detected radio echoes with their physical parameters. Sometimes, the resulting density profiles can be erroneous, not reflecting real ionosphere, probably due to severely disturbed ionosphere in the polar region. In this study, the automatic classification procedure of the estimated electron density profiles is developed to filter out unusable data for the 5-year period from 2017 to 2021. The ionograms are classified into four categories: 'Unavailable', 'Sporadic E', 'Needs Reprocessing', and 'Available'. It is found that approximately 50% of ionograms are evaluated to be reasonable with proper electron density profiles and about 35% of them tend to be affected by sporadic-E like structures, blocking the F-region ionosphere to be observed. It should be noted that the sporadic-E like structures in the polar ionosphere seems to be main obstacles for the ionospheric sounding observation of the F-region ionosphere. Only less than 10% of ionograms are classified as a reprocessing type which needs to be reprocessed. Finally, no echoes are recognized by Dynasonde analysis for about 5% of ionograms. The reprocessing and/or unavailable types might be associated with auroral precipitations that disturbs the ionosphere in the polar region.
7
- Shun-Rong Zhang
- Journal of astronomy and space sciences
- 42, n.4
- pp.119-134
- 2025
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This study investigates high-latitude ionospheric mesoscale irregularities associated with energetic particle precipitation and magnetosphere-ionosphere-thermosphere coupling processes within the auroral oval using ground-based Global Navigation Satellite Systems (GNSS) total electron content (TEC) measurements. This scale size is much larger than those associated with GNSS scintillations, which range from sub-kilometers (small scales) to > 10 km (large scales). Analyzing 15 yr of data from 2010 to 2024, we characterize, for the first time, the climatology of enhanced intensity of ionospheric mesoscale irregularities at high latitudes. The observed intensity of irregularities in GNSS TEC fluctuations can serve as a proxy for the dynamic behavior of the auroral oval which varies with magnetic local time, longitude, latitude, season, solar activity cycle, geomagnetic disturbances, and hemisphere. The spatial distribution of the irregularity is oval-shaped and therefore this pat- tern is named as 'irregularity oval'; the morphology of the irregularity oval is generally aligned well with the known variations of auroral oval established by using other technologies. While the primary goal has been to document systematically these irregularity long-term observations, future work will focus on the development of a novel GNSS TEC-based 'irregularity oval' model.
8
- Robert Vernon Wagner
- Journal of astronomy and space sciences
- 42, n.4
- pp.97-118
- 2025
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Exploration of the lunar poles is accelerating as multiple missions target these regions, with growing interest in studying the environment within permanently shadowed regions (PSRs)-areas at the poles that never receive direct sunlight. To prepare for these exploration activities within PSRs, we determined radiance levels in PSRs of various sizes and derived a conversion factor from ShadowCam radiance units to luminance, which is more suitable for evaluating human factors, as luminance accounts for the wavelength range to which humans are sensitive. Notably, during lunar summer, many PSRs reach luminance levels comparable to those of well-lit buildings for several Earth days each month, while peak winter lighting is typically up to six times dimmer, except in regions where regional shadows predominate and further decrease illumination. As a result, we do not expect artificial light to be needed for missions visiting PSRs during the summer peak lighting period, except for close inspection of samples. In contrast, in winter, diminished ambient lighting may require supplemental illumination for many tasks.
9
- Juhyeong Kim
- Journal of astronomy and space sciences
- 42, n.1
- pp.15-27
- 2025
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The mission-assisting anisotropic magnetoresistive sensor (MAMS) module is one of the components supporting the operation of the lunar surface magnetometer (LSMAG), one of the Korean candidate payloads for the Commercial Lunar Payload Services (CLPS) program. LSMAG uses fluxgate magnetometers (FGMs), which have a 0.2 nT resolution and ± 2,000 nT measurement range. For the scientific analysis of LSMAG data, four types of additional mission-assisting functions are required: strong magnetic field measurement, lander noise detection, offset calibration signal generation, and attitude information provision. To perform these functions, the MAMS module utilizes anisotropic magnetoresistive (AMR) sensors (HMC1001/1002), an accelerometer (ADXL355), and an artificial magnetic field generating circuit. The AMR sensors have a larger measurement range than FGMs. Therefore, these sensors are suitable for measuring strong magnetic fields and the lander's noise signal, making them applicable for noise-removal techniques. The MAMS module also includes an accelerometer (ADXL355) to measure the attitude of the LSMAG boom and features an artificial field-generating function to determine the sensor offset. The MAMS module passed functional and space environmental tests to verify its performance. The AMR sensors have a 20 nT resolution and ± 80,000 nT range, while the accelerometer has a 6 mg resolution and ± 2 g range under Earth conditions. This module includes its own microcontroller unit and supports a wide input voltage range and standard RS485 universal asynchronous receiver/transmitter (UART) communication. We expect the MAMS module to not only play an essential role in supporting LSMAG data calibration and operation, but also to be used in various future space science exploration missions.
10
- Ji Eun Kim
- Journal of astronomy and space sciences
- 42, n.2
- pp.47-61
- 2025
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The tip of the Antarctic Peninsula is widely recognized as one of the most active regions for gravity wave activity. Situated in this dynamic area, the King Sejong Station (KSS: 62.22°S, 58.78°W) serves as an ideal location for investigating gravity wave activity in the mesosphere and lower thermosphere (MLT) region. The Korea Polar Research Institute (KOPRI) has been operating a meteor radar (MR) and an airglow all-sky camera (ASC) at KSS for over a decade, enabling studies on gravity wave activity and MLT dynamics. To enhance these observational capabilities, a new optical instrument, the Advanced Mesospheric Temperature Mapper (AMTM), was installed in January 2023. The KSS-AMTM provides hydroxyl (OH) airglow intensities at approximately 87 km altitude as well as two-dimensional temperature maps at a high temporal resolution. This study presents a brief overview of the observational features and operation of the instrument, alongside initial results obtained over 28 clear nights from February to October 2023. As part of the initial validation, observed mesopause temperatures were compared with data from meteor radar and the Microwave Limb Sounder onboard the Aura satellite.