• Proceedings of the KSRS Conference
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• v.1
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• pp.232-235
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• 2006

Using 30 days of hourly visible channel data and DIScrete Ordinate Radiative Transfer (DISORT) model (6S), Aerosol optical depth (AOD) at $0.55{\mu}m$ was retrieved over the East Asia. In contrast with the AOD retrieval using low-earth-orbit satellites such as MODIS (Moderate-Res olution Spectroradiometer) or MISR (Multiangle Imaging SpectroRadiometer), this algorithm with geostationary satellite can improve the monitoring of AOD without the limitation of temporal resolution. Due to the limited number of channels in the conventional meteorological imager onboard the geostationary satellite, an AOD retrieval algorithm utilizing a single visible channel has been introduced. This single channel algorithm has larger retrieval error of AOD than other multiple-channel algorithm due to errors in surface reflectance and atmospheric property. In this study, the effects of manifold atmospheric and surface properties on the retrieval of AOD from the geostationary satellite, are investigated and compared with the AODs from AERONET and MODIS. To improve the accuracy of retrieved AOD, efforts were put together to minimize uncertainties through extensive sensitivity tests. This algorithm can be utilized to retrieve aerosol information from previous geostationary satellite for long-term climate studies.

• Bulletin of the Korean Space Science Society
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• 2002.05b
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• pp.40-40
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• 2002

• Journal of Astronomy and Space Sciences
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• v.26 no.4
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• pp.635-642
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• 2009

This paper describes the Flight Dynamics Automation (FDA) system for COMS Flight Dynamics System (FDS) and its test result in terms of the performance of the automation jobs. FDA controls the flight dynamics functions such as orbit determination, orbit prediction, event prediction, and fuel accounting. The designed FDA is independent from the specific characteristics which are defined by spacecraft manufacturer or specific satellite missions. Therefore, FDA could easily links its autonomous job control functions to any satellite mission control system with some interface modification. By adding autonomous system along with flight dynamics system, it decreases the operator's tedious and repeated jobs but increase the usability and reliability of the system. Therefore, FDA is used to improve the completeness of whole mission control system's quality. The FDA is applied to the real flight dynamics system of a geostationary satellite, COMS and the experimental test is performed. The experimental result shows the stability and reliability of the mission control operations through the automatic job control.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.49.4-50
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• 2009

We report stray light modeling and analysis results for the current and proposed next generation ocean color imagers with Sun and the target area around Korean penninsular as viewed from geostationary orbit. The imagers used in this study are GOCI of 140mm in diameter and a proposed next generation GOCI (GOCI-II) of about 300mm in diameter. First, we built complete GOCI and GOCI-II 3D optical system models with the realistic surface characteristics. These optical models were incorporated into the in-house built Intergrated Ray Tracing (IRT) algorithm, connecting the Sun, the measurement target area and the instruments via single ray tracing computation for radiative transfer and scattering. The stray light level was then estimated for possible orbital configurations for science measurement and in-orbit calibration operation. The simulation details, results and their implications are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.8
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• pp.87-93
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• 2002

In general, station relocation for a geostationary orbit satellite is formulated as a request for moving the spacecraft from its present longitude to the target longitude within a given time interval. The station relocation maneuver is composed of drift orbit insertion maneuver and target orbit insertion maneuver. During station relocation, the satellite orbit is continually influenced by the non-spherical geo-potential. When we plan a maneuver, if we do not consider the influence, the satellite may not be relocate to desired longitude successfully. To solve this problem, we applied the linearised orbit transfer equation to acquire maneuver time and delta-V. Nonlinear simulation for the station relocation of multiple satellites is performed in order to verify the distance between two satellites.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.199-206
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• 2024

The GEO-KOMPSAT-2A (GK2A) satellite, which was launched in December 2018, carries weather observation payloads and uses the image navigation and registration system to calibrate the observation images. The calibration system requires accurate orbit prediction data and depends on the accuracy of the orbit determination accuracy. In order to find a possible way to improve the current orbit determination accuracy of the GK2A flight dynamic subsystem module, orbit determination software was developed to independently evaluate the orbit determination accuracy. A comprehensive satellite dynamic model is applied for a batch-type least squares filter. When determining the orbit, thrust firing during station-keeping maneuvers and wheel-off loading maneuvers is taken into account. One month of GK2A ranging data were processed to estimate the satellite position on a daily basis. The orbit determination error was evaluated by comparing estimates during overlapping estimation intervals.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.10
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• pp.67-76
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• 2004

This paper improves existing 'fly-the-wire' based autonomous station-keeping system, suitable for geostationary satellite and introduces results of computer simulations conducted to verify the algorithm. The on-board stationkeeping system receives pseudo-range signals from two ground equipments located with long baseline, determines the orbit error in realtime and generates orbit control commands. To reduce fuel consumption, this paper proposes an on-board orbit control logic using modified fly-the-wire method. The modified fly-the-wire method de-couples error components into two dynamic modes, harmonic and linear motion. The harmonic error components are removed by applying output commands produced by feedback controller, and the linear motions are controlled by the correction ${\Delta}V\;s$ added to reference maneuvers. The reference maneuvers are generated through the ground based computer simulation and embedded or uploaded into the on-board computer with time tags. Finally, the performance of the proposed algorithm is verified through a series of computer simulations.

• Aerospace Engineering and Technology
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• v.12 no.2
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• pp.57-63
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• 2013

The mission of a lot of satellites on geostationary orbit is the communication and/or the broadcasting. These satellites need a big power, so these have a large solar array. Recently, the new satellite for Earth environment monitoring is developing on geostationary orbit. The payload of Earth monitoring satellite requires better thermal condition on detector. Therefore this satellite uses a boom for the attitude stability instead of rejecting one-side solar array as a heat source. The other hand, it uses some momentum wheels being a more momentum capacity to control the large disturbance by solar pressure due to the asymmetric solar array configuration. In this paper, the analysis on the wheel allocation and the wheel off-loading for COMS is summarized and the results are verified by telemetry of COMS. COMS has no boom and a perfectly asymmetric solar array configuration, and it is operating well on geostationary orbit.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1057-1064
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• 2014

The satellite on geostationary orbit accommodates multiple payloads into a single spacecraft platform and launched in June 26, 2010. The electrical power required to the satellite during sunlight is generated by a solar array wing. The solar cells are the GaInP/GaAs/Ge Triple Junction cells named Gaget2 cells from RWE Space, which were based on a Spectrolab epitaxy. This paper evaluates solar array power performance at end of design life based on the trend analysis results for the flight data on geostationary orbit. The estimated solar array power performance at end of design life compares with the power performance provided by solar array manufacturer. The solar cells show nominal behavior without significant degradation through the trend analysis results.

• Journal of Astronomy and Space Sciences
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• v.3 no.2
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• pp.93-102
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• 1986

For a geostationary satellite east-west station keeping maneuvers must control both the mean longitude and the orbit eccentricity simultaneously. The effect on the orbit eccentricity of maneuvers may be reprensented by a phse plane of $e_{c}$ verse $e_{s}$, since these eccentricity elements give the projection of the orbit center onto the equatorial plane in units of the semimajor axis. The evolution of the mean longitude and the orbit eccentricity are obtained.