• Journal of Astronomy and Space Sciences
• /
• v.16 no.1
• /
• pp.53-60
• /
• 1999

The purpose of this paper is to predict Sun Transit Outage phenomenon(Sunout). Sunout had been studied mainly for the case of Geostationary satellite and under the assumption of 'Quiet Sun'. In this paper, we predict sunout phenomenon more precisely for non-geostationary orbit as well as geostationary orbit and specially we considered the degree of solar activity. And we compare the result of the case of C-band and Ku-band. Also the result is applied to the two KoreaSat communication system through calculating the link budget.

• Journal of Astronomy and Space Sciences
• /
• v.41 no.1
• /
• pp.17-23
• /
• 2024

The safety of electronic components used in aerospace systems against cosmic rays is one of the most important requirements in their design and construction (especially satellites). In this work, by calculating the dose caused by proton beams in geostationary Earth orbit (GEO) orbit using the MCNPX Monte Carlo code and the MULLASSIS code, the effect of different structures in the protection of cosmic rays has been evaluated. A multi-layer radiation shield composed of aluminum, water and polyethylene was designed and its performance was compared with shielding made of aluminum alone. The results show that the absorbed dose by the simulated protective layers has increased by 35.3% and 44.1% for two-layer (aluminum, polyethylene) and three-layer (aluminum, water, polyethylene) protection respectively, and it is effective in the protection of electronic components. In addition to that, by replacing the multi-layer shield instead of the conventional aluminum shield, the mass reduction percentage will be 38.88 and 39.69, respectively, for the two-layer and three-layer shield compared to the aluminum shield.

• Journal of Astronomy and Space Sciences
• /
• v.14 no.1
• /
• pp.142-149
• /
• 1997

This paper applied one of the well-known optimal control theory, namely, linear quadratic regulator(LQR), to the station-keeping maneuvers(SKM) for a geostationary satellite. The boundary conditions to transfer the system with a good accuracy at a terminal time were based upon the predicted orbital data which are created due to the Earth's non-uniform mass distribution's effect during 14 days and due to luni-solar effect during 28 days. Through the linearization of the nonlinear system equation with respect to reference orbit and the numerical integration of Riccati equation, the optimal trajectories and the corresponding control law have been obtained by using LQR. From the comparison of ${\Delta}V$ obtained by LQR with the ${\Delta}V$ obtained anatically by geometric method, Station Keeping Maneuvers(SKM) via LQR may provide comparable results to a real system. Furthermore it will demonstrate the possibility in fuel optimization and life extension of geostationary satellite.

• Proceedings of the KSRS Conference
• /
• 2002.10a
• /
• pp.615-620
• /
• 2002

Probability distribution of the sea surface slope is estimated using sun glitter images derived from visible radiometer on Geostationary Meteorological Satellite (GMS) and surface vector winds observed by spaceborne scatterometers. The brightness of the visible images is converted to the probability of wave surfaces which reflect the sunlight toward GMS in grids of 0.25 deg $\times$ 0.25 deg. Slope and azimuth angle required for the reflection of the sun's ray toward GMS are calculated for each grid from the geometry of GMS observation and location of the sun. The GMS images are then collocated with surface wind data observed by three scatterometers. Using the collocated data set of about 30 million points obtained in a period of 4 years from 1995 to 1999, probability distribution function of the surface slope is estimated as a function of wind speed and azimuth angle relative to the wind direction. Results are compared with those of Cox and Munk (1954a, b). Surface slope estimated by the present method shows narrower distribution and much less directivity relative to the wind direction than that reported by Cox and Munk. It is expected that their data were obtained under conditions of growing wind waves. In general, wind waves are not always developing, and slope distribution might differ from the results of Cox and Munk. Most of our data are obtained in the subtropical seas under clear-sky conditions. This difference of the conditions may be the reason for the difference of slope distribution.

• Journal of Astronomy and Space Sciences
• /
• v.20 no.4
• /
• pp.313-318
• /
• 2003

A communications satellite system placed in three-Lagrange points, $L_3$, $L_4$ and $L_5$, of the restricted three-body problem in Earth-Moon system is proposed in this paper. LEO satellite constellation has been another choice of communications system. The proposed system which is alternatives of limited geostationary orbit resources, has some weak points such as long distance from the Earth, relatively expensive launch cost, long delay time, more required power, and so on. It has good points like less efforts (fuel) for station keeping, less eclipses, etc. This system has limitations for applications to provide commercial services but it is still some attractive points.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.286-289
• /
• 2006

This paper analyzed the JPEG compression performance of MTSAT-1R(Multi-functional Transport Satellite - 1 Replacement), which is offering the LRIT/HRIT(Low Rate Information Transmissio / High Rate Information Transmission) service now, in order to design the system regarding LRIT/HRIT of COMS(Communication, Ocean and Meteorological Satellite). To do so, we analysed Lossy and Lossless JPEG compression performance regarding the MTSAT-1R LRIT/HRIT data for 10 days, and made comparison to the image characteristics, and understood the JPEG compression characteristics regarding JPEG compression of geostationary meteorological satellite. This result of compression performance analysis is expected to be a reference not only to the system design and realization of COMS LRIT/HRIT but also to those who develop other meteorological satellite receiving systems.

• Korean Journal of Remote Sensing
• /
• v.35 no.1
• /
• pp.57-81
• /
• 2019

Satellite images can be integrated into a crop model to strengthen the advantages of each technique for crop monitoring and to compensate for weaknesses of each other, which can be systematically applied for monitoring inaccessible croplands. The objective of this study was to outline the productivity of paddy rice based on simulation of the yield of all paddy fields in North Korea, using a grid crop model combined with optical satellite imagery. The grid GRAMI-rice model was used to simulate paddy rice yields for inaccessible North Korea based on the bidirectional reflectance distribution function-adjusted vegetation indices (VIs) and the solar insolation. VIs and solar insolation for the model simulation were obtained from the Geostationary Ocean Color Imager (GOCI) and the Meteorological Imager (MI) sensors of the Communication Ocean and Meteorological Satellite (COMS). Reanalysis data of air temperature were achieved from the Korea Local Analysis and Prediction System (KLAPS). Study results showed that the yields of paddy rice were reproduced with a statistically significant range of accuracy. The regional characteristics of crops for all of the sites in North Korea were successfully defined into four clusters through a spatial analysis using the K-means clustering approach. The current study has demonstrated the potential effectiveness of characterization of crop productivity based on incorporation of a crop model with satellite images, which is a proven consistent technique for monitoring of crop productivity in inaccessible regions.

• Proceedings of the KSRS Conference
• /
• v.1
• /
• pp.228-231
• /
• 2006

In this paper, requirements of Meteorological Administration about Meteorological Imager (MI) of Communications, Ocean and Meteorological Satellite (COMS) is analyzed for the design of COMS ground station and according to the analysis results, the distribution image size of each observation area suitable for satellite Field Of View (FOV) stated at the requirements of meteorological administration is determined and the precise satellite FOV and the size of distribution image is calculated on the basis of the image size of the determined observation area. The results in this paper were applied to the detailed design for COMS ground station and also are expected to be used for the future observation scheduling and the scheduling of distribution of user data.

• Proceedings of the KIEE Conference
• /
• 2007.10a
• /
• pp.269-270
• /
• 2007

The COMS(Communication, Ocean & Meteorological Satellite) is the geostationary satellite which will be performing three main objectives such as meteorological service, ocean monitoring and Ka-band satellite communications. This paper reports on the hardware architecture of the system electrical ground support equipment(EGSE) for the COMS satellite. EGSE is used to check out satellite during the development prior to lunch. The EGSE represented in this paper consist of two parts. First, I will deal with the OCOE(Overall Check Out Equipment) system which controls and operates the all EGSE system. In second part, we will introduce the SCOE(Specific Check Out Equipment) systems which can test the specific subsystems of the COMS satellite.

• Journal of the Korean Professional Engineers Association
• /
• v.42 no.6
• /
• pp.53-57
• /
• 2009

Antenna Tracking System has been required core technology with special tracking algorithm, and it can be achieved by program tracking, step tracking, optracking, and monopulse tracking as well. Depend on tracking requirement we might be able to apply eligible tracking method in accordance with Geostationary and Inclined Orbit Satellite. Further, we should deeply consider two important factors in order to act up to customer expectation in quality and system performance including competitive price therefore we need maximized endeavor to upgrade not only tracking system performance, but reduction of product through engineering skill and R&D investment.