• Smart Media Journal
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• v.11 no.4
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• pp.9-18
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• 2022

Recently, research and system using AI is rapidly increasing in various fields. Smart farm using artificial intelligence and information communication technology is also being studied in agriculture. In addition, data-based precision agriculture is being commercialized by convergence various advanced technology such as autonomous driving, satellites, and big data. In Korea, the number of commercialization cases of facility agriculture among smart agriculture is increasing. However, research and investment are being biased in the field of facility agriculture. The gap between research and investment in facility agriculture and open-air agriculture continues to increase. The fields of fruit trees and plant factories have low research and investment. There is a problem that the big data collection and utilization system is insufficient. In this paper, we are proposed the system for determining the fruit tree growth stage using a deep learning-based object detection model. The system was proposed as a hybrid app for use in agricultural sites. In addition, we are implemented an object detection function for the fruit tree growth stage determine.

• Journal of The Korean Astronomical Society
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• v.55 no.4
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• pp.111-121
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• 2022

Based on the light an exoplanet blocks from its host star as it passes in front of it during a transit, the mid-transit time can be determined. Periodic variations in mid-transit times can indicate another planet's gravitational influence. We investigate 83 transits of TrES-1 b as observed from 6-inch telescopes in the MicroObservatory robotic telescope network. The EXOTIC data reduction pipeline is used to process these transits, fit transit models to light curves, and calculate transit midpoints. This paper details the methodology for analyzing transit timing variations (TTVs) and using transit measurements to maintain ephemerides. The application of Lomb-Scargle period analysis for studying the plausibility of TTVs is explained. The analysis of the resultant TTVs from 46 transits from MicroObservatory and 47 transits from archival data in the Exoplanet Transit Database indicated the possible existence of other planets affecting the orbit of TrES-1 and improved the precision of the ephemeris by one order of magnitude. We now estimate the ephemeris to be (2 455 489.66026 BJD_TDB ± 0.00044 d) + (3.0300689 ± 0.0000007) d × epoch. This analysis also demonstrates the role of small telescopes in making precise midtransit time measurements, which can be used to help maintain ephemerides and perform TTV analysis. The maintenance of ephemerides allows for an increased ability to optimize telescope time on large ground-based telescopes and space telescope missions.

• The Journal of Engineering Geology
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• v.32 no.3
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• pp.363-376
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• 2022

An area under construction for a living facility collapsed around 12:48 KST on 13 January 2021 in Sa-dong, Ansan-si, Gyeonggi-do. There were no casualties due to the rapid evacuation measure, but part of the temporary retaining facility collapsed, and several cracks occurred in the adjacent road on the south side. This study used the potential of synthetic aperture radar (SAR) satellite for surface property changes that lies in backscattering characteristic to map the collapsed structure. The interferometric SAR technique can make a direct measurement of the decorrelation among different acquisition dates by integrating both amplitude and phase information. The damage proxy map (DPM) technique has been employed using four high-resolution Constellation of Small Satellites for Mediterranean basin Observation (COSMO-SkyMed) data spanning from 2020 to 2021 during ascending observation to analyze the collapse of the construction. DPM relies on the difference of pre- and co-event interferometric coherences to depict anomalous changes that indicate collapsed structure in the study area. The DPMs were displayed in a color scale that indicates an increasingly more significant ground surface change in the area covered by the pixels, depicting the collapsed structure. Therefore, the DPM technique with SAR data can be used for damage assessment with accurate and comprehensive detection after an event. In addition, we classify the amplitude information using support vector machine (SVM) and maximum likelihood classification algorithms. An investigation committee was formed to determine the cause of the collapse of the retaining wall and to suggest technical and institutional measures and alternatives to prevent similar incidents from reoccurring. The report from the committee revealed that the incident was caused by a combination of factors that were not carried out properly.

• Journal of Advanced Navigation Technology
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• v.16 no.6
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• pp.900-909
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• 2012

Low Earth orbit satellites with satellite navigation receiver use onboard navigation filters for filtering measurement signals and for orbit prediction under signal loss. Precision satellite dynamic models, core of the navigation filter, are studied and a computation program is developed. Gravity acceleration, precision coordinate transform, third-body gravity, atmospheric drag, and solar radiation pressure models are combined into an orbit prediction algorithm, and a proven precision orbit determination software is used to validate the program. Orbit prediction accuracy is analyzed with simulated and flight orbit data. The program meets an accuracy level for onboard real-time navigation filter.

• Journal of Positioning, Navigation, and Timing
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• v.1 no.1
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• pp.65-75
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• 2012

We carry out an error analysis of 24-hour global positioning system (GPS)-very long baseline interferometry (VLBI) (GV) hybrid observation data. In this paper, we focus on the impacts of broadcast and final orbits on the GPS delays of the GV hybrid observation by analyzing the residuals, observed - calculated (O-C) values. The residuals show apparent and consistent biases for L1 and L2 signals, respectively. The scatters of the residuals are around a few nanoseconds. The main cause of those observation errors is the absence of the GPS phase and delay calibration system. Most of the satellites show that the differences between the delays, to which broadcast and final orbits are applied, are about 100 times smaller than the current GV hybrid observation errors. We conclude that GPS delays are not greatly affected by orbit accuracies.

• International Journal of Aeronautical and Space Sciences
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• v.17 no.3
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• pp.391-400
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• 2016

In satellite operations, stable maneuvering of a satellite's onboard antenna to prevent undesirable vibrations to the satellite body is required for high-quality high-resolution images. For this reason, the onboard antenna's angular rate is typically minimized while still satisfying the system requirement that limits the speed of the onboard antenna. In this study, a simple yet effective method, called the ground station searching method, is proposed to reduce the angular rate of a satellite's onboard antenna. The performance of the proposed method is tested using real flight data from the KOMPSAT-3 satellite. Approximately 83% of arbitrarily selected real flight scenarios from 66 test cases show reductions in the onboard antenna's azimuth angular rates. Additionally, reliable solutions were consistently obtained within a reasonably acceptable computation time while generating an onboard antenna tracking profile. The obtained results indicate that the proposed method can be used in real satellite operations and can reduce the operational loads on a ground operator. Although the current work only considers the KOMPSAT-3 satellite as a test case, the proposed method can be easily modified and applied to other satellites that have similar operational characteristics.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.367-377
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• 2015

Atmospheric drag force is an important source of perturbation of Low Earth Orbit (LEO) orbit satellites, and solar activity is a major factor for changes in atmospheric density. In particular, the orbital lifetime of a satellite varies with changes in solar activity, so care must be taken in predicting the remaining orbital lifetime during preparation for post-mission disposal. In this paper, the System Tool Kit (STK$^{(R)}$) Long-term Orbit Propagator is used to analyze the changes in orbital lifetime predictions with respect to solar activity. In addition, the STK$^{(R)}$ Lifetime tool is used to analyze the change in orbital lifetime with respect to solar flux data generation, which is needed for the orbital lifetime calculation, and its control on the drag coefficient control. Analysis showed that the application of the most recent solar flux file within the Lifetime tool gives a predicted trend that is closest to the actual orbit. We also examine the effect of the drag coefficient, by performing a comparative analysis between varying and constant coefficients in terms of solar activity intensities.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.11
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• pp.2261-2270
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• 2015

GIS(Geographic Information System) based Positioning technique uses geographic information to predict which satellites are visible or invisible. GPS positioning has poor positioning accuracy in dense urban area where tall buildings block the satellite signals. In this paper, we proposed GIS based Advanced Positioning technique of Mobile GPS to resolve this problem. Particularly, this technique improves positioning accuracy in dense urban area. It is consist of ephemeris and GIS server. We will inversely estimate pseudorange by using NMEA-0183 output data of mobile GPS. After that, we can find more accurate position by using ephemeris and GIS information.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.12
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• pp.1116-1123
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• 2015

The lifetime of a geostationary satellite depends on the residual propellant amount and therefore the precise residual propellant gauging is very important for the mitigation of economic loss arised from premature removal of satellite from its orbit, satellites replacement planning, slot management and so on. In this paper, the thermal mass method and its uncertainty are described. The residual propellant analysis of a geostationary satellite is simulated based on the KOREASAT data and the uncertainty of thermal mass method is calculated by using the Monte Carlo method. The results of this study show the importance parameter of estimation residual propellant using the thermal mass method.

• Journal of The Korean Astronomical Society
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• v.35 no.1
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• pp.1-7
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• 2002

We have studied the long-term X-ray light curve (2-10 keV) of the luminous Seyfert 1 galaxy MCG-2-58-22 by compiling data, from various X-ray satellites, which together cover more than 20 years. We have found two distinct types of time variations in the light curve. One is a gradual and secular decrease of the X-ray flux, and the other is the episodic increase of X-ray flux (or flare) by a factor of 2-4 compared with the level expected from the secular variation. We detected 3 such flares in total; a representative duration for the flares is $\~$2 years, with intervening quiescent intervals lasting $\~$6-8 years. We discuss a few possible origins for these variabilities. Though a standard disk instability theory may explain the displayed time variability in the X-ray light curve, the subsequent accretions of stellar debris, from a tidal disruption event caused by a supermassive black hole in MCG-2-58-22, cannot be ruled out as an alternative explanation.