• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.1197-1199
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• 2003

ROCSAT-2 mission is to daily image over Taiwan and the surrounding area for disaster monitoring, land use, and ocean surveillance during the 5-year mission lifetime. The satellite will be launched in December 2003 into its mission orbit, which is selected as a 14 rev/day repetitive Sun-synchronous orbit descending over (120 deg E, 24 deg N) and 9:45 a.m. over the equator with the minimum eccentricity. National Space Program Office (NSPO) is developing a ROCSAT-2 Image Processing System (IPS), which aims to provide real-time high quality image data for ROCSAT-2 mission. A simulated ROCSAT-2 image, based on Level 1B QuickBird Data, is generated for IPS verification. The test image is comprised of one panchromatic data and four multispectral data. The qualification process consists of four procedures: (a) QuickBird image processing, (b) generation of simulated ROCSAT-2 image in Generic Raw Level Data (GERALD) format, (c) ROCSAT-2 image processing, and (d) geometric error analysis. QuickBird standard photogrammetric parameters of a camera that models the imaging and optical system is used to calculate the latitude and longitude of each line and sample. The backward (inverse model) approach is applied to find the relationship between geodetic coordinate system (latitude, longitude) and image coordinate system (line, sample). The bilinear resampling method is used to generate the test image. Ground control points are used to evaluate the error for data processing. The data processing contains various coordinate system transformations using attitude quaternion and orbit elements. Through the qualification test process, it is verified that the IPS is capable of handling high-resolution image data with the accuracy of Level 2 processing within 500 m.

• Nuclear Engineering and Technology
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• v.55 no.4
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• pp.1332-1341
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• 2023

Beam position measurement system can not only provide the beam position monitoring, but also be used for global orbit correction to reduce beam loss risk and maximize acceptance. The Beam Position Monitors (BPM) are installed along the synchrotron to acquire beam position with the front-end electronics and data acquisition system (DAQ). To realize high precision orbit measurement in the main heavy ion synchrotron and cooling storage ring of heavy-ion research facility in Lanzhou (HIRFL-CSRm), a series of alignment and calibration work has been implemented on the BPM and its DAQ system. This paper analyzed the tests performed in the laboratory as well as with beam based on the developed algorithms and hardware. Several filtering algorithms were designed and implemented on the acquired BPM raw data, then the beam position and resolution were calculated and analyzed. The results show that the position precision was significantly improved from more than 100 ㎛ to about 50 ㎛ by implementing the new designed filtering algorithm. According to the analyzation of the measurement results and upcoming physical requirements, further upgrade scheme for the BPM DAQ system of CSRm based on field programmable gate array (FPGA) technology was proposed and discussed.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.216-219
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• 2004

In this study, the concept and techniques to generate the level lA, lB and 2A image products have been reviewed. In particular, radiometric and geometric corrections and bands registration used to generate level lA, lB and 2A products have been focused in this study. Radiometric correction is performed to take into account radiometric gain and offset calculated by compensating the detector response non-uniformity. And, in order to compensate satellite altitude, attitude, skew effects, earth rotation and earth curvature, some geometric parameters for geometric corrections are computed and applied. Bands registration process using the matching function between a geometry, which is called 'reference geometry', and another one which is corresponds to the image to be registered is applied to images in case of multi-spectral imaging mode. In order to generate level-lA image products, a simple radiometric processing is applied to a level-0 image. Level-lB image has the same radiometry correction as a level-lA image, but is also issued from some geometric corrections in order to compensate skew effects, Earth rotation effects and spectral misregistration. Level-2A image is generated using some geo-referencing parameters computed by ephemeris data, orbit attitudes and sensor angles. Level lA image is tested by visual analysis. The difference between distances calculated level 1 B image and distances of real coordinate is tested. Level 2A image is tested Using checking points.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.3
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• pp.221-235
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• 2024

Errors included in Global Navigation Satellite System (GNSS) measurements degrade the performance of user position estimation but can be mitigated by spatial correlation properties. Augmentation systems providing correction data can be broadly categorized into State Space Representation (SSR) and Observation Space Representation (OSR) methods. The satellite-based cm-level augmentation service based on the SSR broadcasts correction data via satellite signals, unlike the traditional Real-Time Kinematic (RTK) and Network RTK methods, which use OSR. To provide a large amount of correction data via the limited bandwidth of the satellite communication, efficient message structure design considering service area, correction generation, and broadcast intervals is necessary. For systematic message design, it is necessary to analyze the influence of error components included in GNSS measurements. In this study, errors in satellite orbits, satellite clocks for GPS, Galileo, BeiDou, and QZSS satellite constellations ionospheric and tropospheric delays over one year were analyzed, and their spatial decorrelations and linear modeling characteristics were examined.

• Journal of Astronomy and Space Sciences
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• v.22 no.1
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• pp.21-34
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• 2005

The initial conditions that generate bounded motion in eccentric reference orbit are determined for satellite formation flying. Because Hill's equations cannot describe the relative motion between two satellites in eccentric orbit, a new relative dynamics utilizing the nonlinearity and eccentricity correction for Hill's initial conditions is implemented. The constraint that matches angular rates of chief and deputy satellites is used to obtain the bounded motion between them. The constraint can be applied to satellite formation motions in eccentric orbit, since it implicates J2 perturbation due to the central body's aspherical gravitational forces. The periodic bounded motions are analyzed for the orbit with the eccentricity of less than 0.05 and about 0.5 km relative distance between chief and deputy satellites. It is mainly illustrated that the satellite formations in small eccentric orbits can have hounded motions; consequently, the formation can be kept by matching angular rates of the satellites. These results demonstrate an useful method that reduces the cost for operating satellites by providing effective initial conditions for satellite formation flying in eccentric orbit.

• Archives of Plastic Surgery
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• v.36 no.5
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• pp.617-622
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• 2009

Purpose: Endoscopic transnasal correction of the blowout fractures has many advantages over other techniques. But after removal of packing material, there were some patients with recurrence of preoperative symptoms. Authors tried to make a quantitative anterograde analysis of orbital volume change over whole perioperative period which might be related with recurrence of preoperative symptoms. Methods: 10 patients with pure medial wall fracture(Group I) and 10 patients with medial wall fracture combined with fracture of orbital floor(Group II) were selected to evaluate the final orbital volume change, who took 3 CT scans, pre-, postoperative and 4 months after packing removal. By multiplying cross - section area of orbit in coronal view with section thickness, orbital volume were calculated. Then, mean orbital volume increment after trauma, mean orbital volume decrement after endoscopic correction and volume increment after packing removal were found out. And we tried to find correlations between type of fracture, initial correction rate and final correction rate. Results: The mean orbital volume increment of the fractured orbits were 7.23% in group I and 13.69% in group II. After endoscopic surgery, mean orbital volume decrement were 11.0% in group I and 12.46% in group II. Mean volume increment after packing removal showed 3.10% in group I and 6.50% in group II. The initial correction rate(%) showed linear correlation with final correction rate(%) after packing removal. And there were negative linear correlation between increment percentage of orbital volume by fracture and final correction rate(%). Conclusion: Orbital volume was proved to be increasing after removal of packing or foley catheter and it was dependent upon type of fracture. Overcorrection should be done to improve the final result of orbital blowout fracture especially when there are severe fracture is present.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.589-592
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• 2005

Gravity characteristics and Moho undulations are investigated in the Korean peninsula by using satellite gravity data. According to the development of satellite geodesy, gravity potential models which have high accuracy and resolution were released. Using the EIGEN-CGOIC model based on low orbit satellite data such as CHAMP and GRACE, geoid and gravity anomaly were calculated by spherical harmonic analysis. The study area is located at $123^{\circ}\sim132^{\circ}E, 33^{\circ}\sim43^{\circ}$N including Korea. Free-air anomalies, which show the effect of terrain, have the values between $-37\sim724 mgal. After Bouguer correction, the range of simple Bouguer anomalies is $-221\sim246$ mgal. Complete Bouguer anomalies after terrain correction increase from continent to marine. This phenomenon is related rise of Moho discontinuity. The cut-frequency for extraction of Moho undulation was determined by power spectrum analysis, and then 3D inversion modeling was implemented. The mean, maximum, minimum, and standard deviation of Moho depth undulation are -26, -36, -8, and 4.9 krn, respectively.

• Proceedings of the KSRS Conference
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• v.1
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• pp.79-81
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• 2006

Geostationary ocean satellite, unlike other sun-synchronous polar-orbit satellites, will be able to take a picture of a large region several times a day (almost with every one hour interval). For geostationary satellite, the target region is fixed though the location of sun is changed always. Thus, the ocean signal of a given target point is largely dependent on time. In other words, the ocean signal detected by geostationary satellite sensor must translate to the signal of target when both sun and satellite are located in nadir, using another correction model. This correction is performed with a standardization of signal throughout relative geometric relationship among satellite - sun - target points. One signal value of a selected pixel point of the target region of Geostationary Ocean Colour Imager (GOCI) would be set up as a standard, and the ratio of all remained pixel point can be calculated. This relative ratio called bidirectional factor, the result of modelling of spatiotemporal variation of bidirectional factor is shown.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.35 no.3
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• pp.184-188
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• 2013

Post-traumatic enophthalmos is a relatively common problem following orbitozygomatic fractures. Bony-volume expansion and soft tissue atrophy are considered the main etiological causes of this condition. Enophthalmos is corrected mostly through reducing the enlarged orbit volume. Autogenous graft and various alloplastic materials are used for this purpose. Porous polyethylene is highly biocompatible, durable, and remarkably stable. Also, the titanium plate embedded in a porous polyethylene sheet provides radiographic visibility and increased sheet strength and contour retention. We present experiences of titanium reinforced porous polyethylene for correction of the traumatic enophthalmos with literature review.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.8
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• pp.574-581
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• 2019

This paper investigates the effects of thrust misalignments and offsets of the lateral center of gravity of a space launch vehicle on its guidance performance. Sensitivity analysis and Monte Carlo simulations are applied to analyze their effects by computing changes in orbit injection errors when including the error sources. To compensate their effects, the attitude controller including an integrator additionally and the Steering Misalignment Correction (SMC) routine of the Saturn V are considered, and then Monte Carlo simulations are performed to evaluate their performances.