• Journal of Astronomy and Space Sciences
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• v.34 no.1
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• pp.55-65
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• 2017

We studied the hour-lines of six extant Yangcheon-cheoks in Korea. To find whether Yangcheon-cheok was used in the whole area of Korea, we calculated the length of shadows of Yangcheon-cheok on the Korean Peninsula, Nanjing and Beijing as well as Hanyang (Seoul), according to 24 solar terms. Comparing the length of shadows with hour-lines of those relics, we could find that Yangcheon-cheok was suitable for use at limited times (from 9:00 to 15:00) during the year. Also, this sundial is more appropriate for use at low latitudes than high ones. Among existing relics, that of Seoul Museum of History made with porcelain was much more suitable to use at Hanyang and its higher latitude. Lee's collection was also suitable to use at Nanjing. It is certain that Yangcheon-cheok was a portable sundial which could be used from nine to fifteen of clock all the year around except for the winter season.

• Journal of Astronomy and Space Sciences
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• v.27 no.3
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• pp.213-220
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• 2010

As an observation instrument of the longest record of tropospheric water vapor, radiosonde data provide upper-air pressure (geopotential height), temperature, humidity and wind. However, the data have some well-known elements related to inaccuracy. In this article, radiosonde precipitable water vapor (PWV) at Sokcho observatory was compared with global positioning system (GPS) PWV during each summertime of year 2007 and 2008 and the biases were calculated. As a result, the mean bias showed negative values regardless of the rainfall occurrence. In addition, on the basis of GPS PWV, the maximum root mean square error (RMSE) was 5.67 mm over the radiosonde PWV.

• Journal of Astronomy and Space Sciences
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• v.33 no.1
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• pp.55-62
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• 2016

Heumgyeonggaknu (欽敬閣漏) is powered by a water-hammering-type water wheel. The technique that maintains the constant speed of the water wheel is assumed to be the one used in the Cheonhyeong (天衡) apparatus in Shui Yun Yi Xiang Tai (水運儀象臺) made by the Northern Song (北宋) dynasty in the 11^th century. We investigated the history of the development and characteristics of the Cheonhyeong apparatus, and we analyzed ways to transmit the power of Heumgyeonggaknu. In addition, we carried out a conceptual design to systematically examine the power control system. Based on the conceptual design, we built a model for a water wheel control system that could be used in experiments by drawing a 3D model and a basic design.

• Journal of Astronomy and Space Sciences
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• v.27 no.2
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• pp.81-88
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• 2010

A total of 583 observations (193 in ${\Delta}b$, 190 in ${\Delta}v$, 200 in ${\Delta}r$) for V523 Cas was made on 9 nights from September to December in 2008 using the 100 cm telescope with 2K CCD camera of the Chungbuk National University Observatory. With our data BVR light curves were constructed and 9 times of minimum light were determined. We also obtained physical parameters of the V523 Cas system by analysis of the BVR light curves using the Wilson-Devinney code.

• Journal of Astronomy and Space Sciences
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• v.31 no.3
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• pp.205-214
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• 2014

In this study, a star identification algorithm which utilizes pivot patterns instead of apparent magnitude information was developed. The new star identification algorithm consists of two steps of recognition process. In the first step, the brightest star in a sensor image is identified using the orientation of brightness between two stars as recognition information. In the second step, cell indexes are used as new recognition information to identify dimmer stars, which are derived from the brightest star already identified. If we use the cell index information, we can search over limited portion of the star catalogue database, which enables the faster identification of dimmer stars. The new pivot algorithm does not require calibrations on the apparent magnitude of a star but it shows robust characteristics on the errors of apparent magnitude compared to conventional pivot algorithms which require the apparent magnitude information.

• Journal of Astronomy and Space Sciences
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• v.19 no.4
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• pp.283-292
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• 2002

Electronic boards of Far-ultraviolet IMaging Spectrograph (FIMS) should be designed to maintain their performances, and their temperatures should be remained within the allowed temperatures in operational environments. Thermal analysis at the electronic board level has been performed, and it is confirmed the electronics parts could be kept within their allowed temperature ranges.

• Journal of Astronomy and Space Sciences
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• v.33 no.4
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• pp.319-321
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• 2016

Reviewing the two MeV-GeV investigations in the field of the HESS J1745-303 performed using Fermi Large Area Telescope data, we confirmed that the emission peak comfortably coincides with 'Region A' in the TeV regime, which is the brightest part of this feature. The MeV-TeV spectrum can be precisely described by a single power-law. Also, recent investigation has shown that the MeV-GeV feature is elongated from 'Region A' toward the north-west, which is similar to the case of largescale atomic/molecular gas distribution.

• Journal of Astronomy and Space Sciences
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• v.37 no.4
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• pp.219-228
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• 2020

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

• Journal of Astronomy and Space Sciences
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• v.39 no.3
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• pp.109-116
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• 2022

The small-scale magnetospheric and ionospheric plasma experiment (SNIPE) is a mission initiated by the Korea Astronomy and Space Science Institute (KASI) in 2017 and comprises four 6U-sized nano-satellites (Korea Astronomy and Space Science Institute Satellite-1, KASISat-1) flying in formations. The main goal of the SNIPE mission is to investigate the space environment in low Earth orbit at 500-km. Because Iridium & GPS Board (IGB) is installed on the KASISat-1, a communication simulation is required to analyze the contact number and the duration. In this study, communication simulations between the Iridium satellite network and KASISat-1 are performed using STK Pro (System Tool Kit Pro Ver 11.2) from the AGI (Analytical Graphics, Inc.). The contact number and durations were analyzed by each orbit and date. The analysis shows that the average access number per day is 38.714 times, with an average of 2.533 times per orbit for a week. Furthermore, on average, the Iridium satellite communication is linked for 70.597 min daily. Moreover, 4.625 min is the average duration of an individual orbit.

• Journal of Space Technology and Applications
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• v.3 no.4
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• pp.301-321
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• 2023

The Journal of Astronomy and Space Sciences (JASS) has published research papers on a range of topics since its initial publication in 1984, giving space science researchers a platform. In this paper, we reviewed recent publications (2019-2023) that deal with the space environment. In the space environment field, we reviewed 37 papers published in JASS during this time, covering research topics such as the sun, magnetosphere, ionosphere, atmosphere, and space radiation. We hope that researchers in the field will make use of this in the future as it will allow us to share the most recent trends in the field of space environment research that is currently underway.