• Journal of the Semiconductor & Display Technology
• /
• v.17 no.4
• /
• pp.91-96
• /
• 2018

In this study temperature distribution and gas flow inside a planetary type reactor in which a number of satellites on a spinning susceptor were rotating were analyzed using numerical simulation. Effects of flow rates on gas flow and temperature distribution were investigated in order to obtain design parameters. The commercial computational fluid dynamics software CFD-ACE+ was used in this study. The multiple-frame-of-reference was used to solve continuity, momentum and energy conservation equations which governed the transport phenomena inside the reactor. Kinetic theory was used to describe the physical properties of gas mixture. Effects of the rotation speed of the satellites was clearly seen when the inlet flow rate was small. Thickness of the boundary layer affected by the satellites rotation became very thin as the flow rate increased. The temperature field was little affected by the incoming flow rate of precursors.

• Journal of Aerospace System Engineering
• /
• v.15 no.4
• /
• pp.1-6
• /
• 2021

The non-explosive holding and release mechanism is used to prevent damage to the mission component caused by explosives when the deployment structure for Cube Satellites is separated. However, among the several types available, the non-explosive holding and release mechanism system using nylon wires depend on the nylon wire knot method and tightening power of the worker. Therefore, in this study, we conducted experiments with the operation of a new holding and release mechanism system by conceptualizing the Boa System Dial, which can provide a constant tightening force regardless of worker proficiency and deploying a imitational solar panel. In this study, the process of binding and unbinding with constant tension was recorded while applying the novel non-explosive holding and release mechanism using the Boa System Dial proposed. In addition, required advances are indicated for the application of the proposed system to actual Cube Satellites.

• Journal of Space Technology and Applications
• /
• v.2 no.2
• /
• pp.169-186
• /
• 2022

In this article, Russia's space threat assessment and space warfare in the Russia-Ukraine war (Russian invasion of Ukraine) were analyzed and summarized. Considering the probability that commercial satellites will also be potential targets of space warfare, it is suggested that not only military satellites but also commercial satellites develop and apply space technology that can be applied equally to space threats when developing space technology. Necessary space technologies is listed.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.24 no.4
• /
• pp.41-54
• /
• 2021

It is very essential to estimate the water body area using remote exploration for water resource management, analysis and prediction of water disaster damage. Hydrophysical detection using satellites has been mainly performed on large satellites equipped with optical and SAR sensors. However, due to the long repeat cycle, there is a limitation that timely utilization is impossible in the event of a disaster/disaster. With the recent active development of Micro satellites, it has served as an opportunity to overcome the limitations of time resolution centered on existing large satellites. The Micro satellites currently in active operation are ICEYE in Finland and Capella satellites in the United States, and are operated in the form of clusters for earth observation purposes. Due to clustering operation, it has a short revisit cycle and high resolution and has the advantage of being able to observe regardless of weather or day and night with the SAR sensor mounted. In this study, the operation status and characteristics of micro satellites were described, and the water area estimation technology optimized for micro SAR satellite images was applied to the Daecheong Dam basin on the Korean Peninsula. In addition, accuracy verification was performed based on the reference value of the water generated from the optical satellite Sentinel-2 satellite as a reference. In the case of the Capella satellite, the smallest difference in area was shown, and it was confirmed that all three images showed high correlation. Through the results of this study, it was confirmed that despite the low NESZ of Micro satellites, it is possible to estimate the water area, and it is believed that the limitations of water resource/water disaster monitoring using existing large SAR satellites can be overcome.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.20 no.1
• /
• pp.85-97
• /
• 2017

In recent years, the damage scales of water disasters such as typhoons, tsunamis, and heavy snow have been increasing globally as a result of global warming and climate changes. In particular, the economic loss caused by typhoons has been increasing for overpopulated areas that have undergone economic development and urbanization since the 1960s. In this study, we investigated and analyzed satellite images captured before and after typhoons on the Korean peninsula, including Typhoon Chaba (2016), Typhoon Rusa ('02), and Typhoon Maemi ('03). There was a limitation in utilizing existing satellites. Domestic satellites have mostly been developed and operated for the observation of the weather, ocean, and topography, as well as for use in communication. There are therefore insufficient temporal and spatial observations for water management and disaster response. In this work, we expanded the scope to overseas satellites and collected data from GMS, TRMM, COMS, and GPM. In the future, it will be necessary to develop and launch water resources satellites that can provide sufficient temporal and spatial data analysis units to obtain rapid and accurate water hazard information for the Korean peninsula.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.32 no.3
• /
• pp.233-244
• /
• 2014

Precise Point Positioning (PPP) is an increasingly recognized precisely the GPS/GNSS positioning technique. In order to improve the accuracy of PPP, the error sources in PPP measurements should be reduced as much as possible and the ambiguities should be correctly resolved. The correct ambiguity resolution requires a careful control of residual errors that are normally categorized into random and systematic errors. To understand effects from two categorized errors on the PPP ambiguity resolution, those two GPS datasets are simulated by generating in locations in South Korea (denoted as SUWN) and Hong Kong (PolyU). Both simulation cases are studied for each dataset; the first case is that all the satellites are affected by systematic and random errors, and the second case is that only a few satellites are affected. In the first case with random errors only, when the magnitude of random errors is increased, L1 ambiguities have a much higher chance to be incorrectly fixed. However, the size of ambiguity error is not exactly proportional to the magnitude of random error. Satellite geometry has more impacts on the L1 ambiguity resolution than the magnitude of random errors. In the first case when all the satellites have both random and systematic errors, the accuracy of fixed ambiguities is considerably affected by the systematic error. A pseudorange systematic error of 5 cm is the much more detrimental to ambiguity resolutions than carrier phase systematic error of 2 mm. In the $2^{nd}$ case when only a portion of satellites have systematic and random errors, the L1 ambiguity resolution in PPP can be still corrected. The number of allowable satellites varies from stations to stations, depending on the geometry of satellites. Through extensive simulation tests under different schemes, this paper sheds light on how the PPP ambiguity resolution (more precisely L1 ambiguity resolution) is affected by the characteristics of the residual errors in PPP observations. The numerical examples recall the PPP data analysts that how accurate the error correction models must achieve in order to get all the ambiguities resolved correctly.

• Journal of Aerospace System Engineering
• /
• v.13 no.3
• /
• pp.23-31
• /
• 2019

The design requirements of modern satellites vary depending on the purpose of operation. Like conventional medium and large-scale satellites, small satellites which operate on low orbit may also serve military purposes. As a result, there is increased demand for high-resolution photos and videos and multi-target observation becomes important. The most important design parameter for multi-target observation is the satellites' maneuverability. For increased maneuverability, the miniaturization is required to increase the stiffness of the satellite as this decreases the mass moment of inertia of the satellite. In the case of a solar panel having relatively low stiffness compared to the satellites' body, vibrations are generated when the attitude maneuver is performed, which greatly influences the image acquisition. For verification of such vibrational characteristics, the satellites is modeled as a reduced model, and experimental zig for simulating attitude maneuver is introduced. A rigidity simulator for simulating the stiffness of the satellite is also proposed. Additionally, the objective of the experimental method is to simulate the maneuvering angle of the satellite based on the winding length of the wire using a step motor, and to experimentally verify the vibration characteristics of the satellite body and the solar panel generated during the maneuvering test.

• Journal of The Korean Astronomical Society
• /
• v.25 no.2
• /
• pp.105-109
• /
• 1992

We show that spacing patterns of planets and satellites in the solar system are formulatable in a single form. It is suggested that a possible explanation for the rule might be the orbital resonance effect, which has existed at an earlier epoch of the solar (planet) system. By extrapolating the formulated spacing patterns beyond the sun-Pluto distance, we find the sun-Planet X distance falls in a range ($46{\sim}79$) A. U..

• Journal of Aerospace System Engineering
• /
• v.4 no.4
• /
• pp.37-43
• /
• 2010

Need for agile satellites increases for performing various mission due to increase of satellite image applications and users. This paper performs attitude maneuver analysis by using Satellite Tool Kit(STK) made by AGI. In order to automate the STK analysis process, a MATLAB program is developed to generate STK input data and to process STK output data. Five attitude maneuver modes are analyzed and attitude angle variation and required torques are calculated.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.5B
• /
• pp.530-538
• /
• 2011

In this paper, the feasibility of LEO(low earth orbit) satellite-based automatic identification system (SAT-AIS) for the coastal area of the South Korea is evaluated in the context of ship AIS transmission detection probability. We evaluate and compare AIS signal detection probability of ORBCOMM satellites and LEO-one satellites considering link budget, SOTDMA protocol and satellite's swath width. The simulation determines the total number of vessels served by those satellites according to satellite's swath width and thus, By simulation results, the ORBCOMM SAT-AIS system outperforms LEO-one SAT-AIS system. The suggested ORBCOMM based SAT-AIS system can be a solution to resolve the existing limited transmission distance problem of the conventional ship-to-shore AIS system.