• Journal of Astronomy and Space Sciences
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• v.37 no.4
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• pp.237-247
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• 2020

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.

• Journal of Astronomy and Space Sciences
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• v.40 no.2
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• pp.79-88
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• 2023

On Aug. 4, 2022, at 23:08:48 (UTC), the Korea Pathfinder Lunar Orbiter (KPLO), also known as Danuri, was launched using a SpaceX Falcon 9 launch vehicle. Currently, KPLO is successfully conducting its science mission around the Moon. The National Aeronautics and Space Administration (NASA)'s Deep Space Network (DSN) was utilized for the successful flight operation of KPLO. A great deal of joint effort was made between the Korea Aerospace Research Institute (KARI) and NASA DSN team since the beginning of KPLO ground system design for the success of the mission. The efficient utilization and management of NASA DSN in deep space exploration are critical not only for the spacecraft's telemetry and command but also for tracking the flight dynamics (FD) operation. In this work, the top-level DSN interface architecture, detailed workflows, DSN support levels, and practical lessons learned from the joint team's efforts are presented for KPLO's successful FD operation. Due to the significant joint team's efforts, KPLO is currently performing its mission smoothly in the lunar mission orbit. Through KPLO cooperative operation experience with DSN, a more reliable and efficient partnership is expected not only for Korea's own deep space exploration mission but also for the KARI-NASA DSN joint support on other deep space missions in the future.

• Publications of The Korean Astronomical Society
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• v.25 no.4
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• pp.155-165
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• 2010

In this study, we investigate the changes in the equatorial lodge degrees and polar distance degrees of determinative stars in the ancient Chinese archives. Confirmed is the fact that the coordinate values of those determinative stars defined in B.C. 104 had been used until the 8th century but were modified by the observations of Li Chunfeng (李淳風) in the early 7th century and Yixing (一行) in 723 A.D. The results of this study are compared with those in History of Chinese Astronomical Observations of Pan Nai. By applying the results of comtemporary astrodynamical calculations, their reliability is checked, and the corrected catalogues of Shi Shi (石氏) and Yixing are provided. The positional accuracy of those observations is estimated to be one degree.

• Journal of Astronomy and Space Sciences
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• v.31 no.2
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• pp.131-140
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• 2014

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.

• Journal of Astronomy and Space Sciences
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• v.40 no.4
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• pp.149-171
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• 2023

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.

• Publications of The Korean Astronomical Society
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• v.30 no.2
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• pp.715-718
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• 2015

Astronomy is a popular topic for the public in term of astronomical phenomenon such as occultations, solar and lunar eclipses or meteor showers. In term of education, astronomy also is popular as one of the world Science Olympiads. Social media, as the new trend in communicating and connecting people, plays a significant role in increasing the size of the astronomy community. Beyond IYA 2009, more and more astronomy activities have been done in many places in Indonesia. New astronomy communities have been formed in several cities and public engagement is also high in social media especially on Facebook and Twitter. In this paper, we will discuss the lesson learned from astronomy outreach achievements in Indonesia and the need for citizen science projects as a distance learning tool for the public as part of astronomy development in Indonesia. We argue and propose that this project will be also important up to a regional scope.

• Journal of architectural history
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• v.10 no.2 s.26
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• pp.7-19
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• 2001

Ip-am valley, located at the eastern remote part of Korean peninsular was the place where a remarkable Confucian scholar Chang Hyon-gwang spent his secluded days. A large upright stone, called Ip-am, and undulating streams nearby were surrounded by mountains, which formed a large enclosed valley. After selecting 28 natural and artificial places, Chang named each of them. Chang compared the relationship between Ip-am and the 28 places with that of the Polestar and 28 Lunar Lodgings, which were known as the ancient Chinese astronomical concept. Also, Chang regarded the valley as a place where the Taoistic Deity could stay. Chang, who had deep knowledge of astronomy, wrote some books on it. It could be said that the comparison of his hermitages with the Polestar and the 28 Lunar Lodgings resulted from his deep passion for astronomy. He considered the Ip-am valley to be the core of the universe like the Polestar is the core of the celestial world. Some stars like the Polestar or the Dipper were regarded as the Deities of Taoism. We can find that Confucian scholars of the middle Choseon, like Chang Hyon-gwang, also tended to have some concern about Taoism.

• Publications of The Korean Astronomical Society
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• v.32 no.3
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• pp.407-420
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• 2017

We study the operation of a lunisolar calendar in Korea and its time data calculation method. The dates based on the lunisolar calendar have been conventionally used in Korea after the Gregorian calendar was introduced in 1896. With the Astronomy Act enacted in 2010, the lunisolar calendar is presently being used as an official calendar along with the Gregorian calendar. However, no institutionalized regulations have been provided on the time data calculation method by the lunisolar calendar. The Korea Astronomy and Space Science Institute very recently established the regulations on the lunisolar calendar operation in Korea. We introduce the regulations together with historical substances and analyze the time data calculated according to the regulations for 600 years from 1901 to 2500. From our study, we find that the value of ${\Delta}T$ (i.e., the difference between the terrestrial time and the universal time) is the most critical parameter causing uncertainty on the data. We also find that all new Moon days in the almanacs agree with our calculations since 1912. Meanwhile, we find that new Moon and winter solstice times are found to be very close to midnight in 38 and five cases, respectively. For instance, the new Moon time on January 14, 2097 is 0 h 0 min 8 s. In this case, deciding the first day (i.e., new moon day) in a lunar month is difficult because of the large uncertainty in the value of ${\Delta}T$. Regarding with a lunar leap month, we find that the rules of inserting the leap month do not apply for 17 years. In conclusion, we believe that our findings are helpful in determining calendar days by using the lunisolar calendar.

• Publications of The Korean Astronomical Society
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• v.14 no.2
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• pp.129-137
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• 1999

We arranged ancient Korean calendar during Koryo dynasty (A.D. 918-1392) according to Julian calendar. We used two representative history books, Koryo-sa (高麗史) and Koryo-sa Jeolyo (高麗史節要), which contain thea stronomical and the historical records chronologically. We found all 19,727 ganji dates(日辰) and 102 misrecoreded ganji dates in two books. Most of the data are arranged based on those two books, and doubtful data are identified using the eclipse, historical events and lunar phase calculations etc. Although Korea, China, and Japan were using basically the same calendar since ancient times, their calendars show some significant disagreement. We found that arranged chronological tables during Koryo dynasty were, in some cases, different from those of China and Japan.

• Journal of Astronomy and Space Sciences
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• v.21 no.4
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• pp.505-528
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• 2004

We have reproduced the records of lunar occultation recorded in the History of Three Kingdoms(삼국사기), the History of the Koryo Dynasty (고려사), the Annals of the Choson Dynasty (朝鮮王朝實錄), the Daily Records of Royal Secretariat of the Choson Dynasty (승정원일기), and obtained the epochs of their realizations. We analysed these results to understand how the system of hours had been kept and when a day began. During most of the periods encompassed by these annals, the 12 double hours(12진각법) and the system of 100 divisions of the day (백각법) had been used when the lunar and the solar eclipses were calculated by royal astronomers. In these systems, the starting point of a day is midnight. On the other hand, the five watch system of hours (경점법), in which a night is divided into five watches, was also used. In this system, a day begins at the sunrise. We found that the traditional twilight, called dusk and dawn (혼명) and used in the east Asian countries, largely corresponds to the nautical twilight in modern concepts. This fact means that the Korean expressions and words for time system in every day life had originated form the five watch system of hours. We pointed out that the sunrise and sunset were convenient boundary lines to ancient astronomers, as well as to farmers in the agricultural society. Our results can be used to determine the exact epoch of each astronomical record in chronicles.