• 대한원격탐사학회지
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• 제37권5_1호
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• pp.1043-1059
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• 2021

식량자원의 확보와 환경생태계에 매우 중요한 요소인 산림과 농경지는 정기적인 모니터링이 요구된다. 농림 위성 영상 자료는 우리나라의 기존 산림 및 농경지 모니터링 방법의 보완재로 효과적으로 활용될 것으로 예상되고 있다. 농림위성의 발사 이전에 사전연구로써 목표 수직기하정확도 산정을 위해 수치표고모델 분석을 수행하였다. 특히 농림위성의 주요 관심 지역인 우리나라 산악지역과 농경지의 특성을 고려하여, 경사도와 식생에 따른 분석을 수행하였다. 공주, 제주 그리고 삼척 지역에 대하여 Shuttle radar topography mission digital elevation model과 Copernicus digital elevation model를 가을과 겨울에 촬영한 드론 LiDAR 수치표면모델 그리고 국토지리정보원 5 m 수치지형모델을 기준으로 평균 상대오차를 비교했다. 그 결과 Shuttle radar topography mission digital elevation model은 8.35, 8.19, 그리고 7.49 m의 상대오차를 나타냈으며, Copernicus digital elevation model는 각각 5.65, 6.73, 그리고 7.39 m의 상대 고도 오차를 나타냈다. 남한 전체에 대하여 Shuttle radar topography mission digital elevation model과 Copernicus digital elevation model를 국토지리정보원 5 m 수치지형모델을 기준으로 지형 경사에 따른 상대 고도 오차를 나타냈다. 그 결과 경사도 0°~5° 사이에서 Shuttle radar topography mission digital elevation model과 Copernicus digital elevation model의 상대 고도 오차는 각각 약 3.62와 2.52 m로 Shuttle radar topography mission digital elevation model의 오차가 더 큰 것으로 산출되었다. 하지만 경사도가 증가함에 따라 이러한 양상은 반전되어 경사도 35° 이상에서는 각각 10.16, 그리고 11.62 m 로 Copernicus digital elevation model의 상대오차가 더 크게 나타났다.

• Journal of Astronomy and Space Sciences
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• 제31권1호
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• pp.51-61
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• 2014

In this work, the preliminary analysis on both the tracking schedule and measurements characteristics for the spacecraft on the phase of lunar transfer and capture is performed. To analyze both the tracking schedule and measurements characteristics, lunar transfer and capture phases' optimized trajectories are directly adapted from former research, and eleven ground tracking facilities (three Deep Space Network sties, seven Near Earth Network sites, one Daejeon site) are assumed to support the mission. Under these conceptual mission scenarios, detailed tracking schedules and expected measurement characteristics during critical maneuvers (Trans Lunar Injection, Lunar Orbit Insertion and Apoapsis Adjustment Maneuver), especially for the Deajeon station, are successfully analyzed. The orders of predicted measurements' variances during lunar capture phase according to critical maneuvers are found to be within the order of mm/s for the range and micro-deg/s for the angular measurements rates which are in good agreement with the recommended values of typical measurement modeling accuracies for Deep Space Networks. Although preliminary navigation accuracy guidelines are provided through this work, it is expected to give more practical insights into preparing the Korea's future lunar mission, especially for developing flight dynamics subsystem.

• Journal of Astronomy and Space Sciences
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• 제37권3호
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• pp.199-208
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• 2020

This paper presents a kinematic ephemeris generator for Korea Pathfinder Lunar Orbiter (KPLO) and its performance test results. The kinematic ephemeris generator consists of a ground ephemeris compressor and an onboard ephemeris calculator. The ground ephemeris compressor has to compress desired orbit propagation data by using an interpolation method in a ground system. The onboard ephemeris calculator can generate spacecraft ephemeris and the Sun/Moon ephemeris in onboard computer of the KPLO. Among many interpolation methods, polynomial interpolation with uniform node, Chebyshev interpolation, Hermite interpolation are tested for their performances. As a result of the test, it is shown that all the methods have some cases that meet requirements but there are some performance differences. It is also confirmed that, the Chebyshev interpolation shows better performance than other methods for spacecraft ephemeris generation, and the polynomial interpolation with uniform nodes yields good performance for the Sun/Moon ephemeris generation. Based on these results, a Kinematic ephemeris generator is developed for the KPLO mission. Then, the developed ephemeris generator can find an approximating function using interpolation method considering the size and accuracy of the data to be transmitted.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.780-783
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• 2006

The KOrea Multi-Purpose Satellite-2 (KOMPSAT-2) was launched in July 2006 and the main mission of the KOMPSAT-2 is a high resolution imaging for the cartography of Korea peninsula by utilizing Multi Spectral Camera (MSC) images. The camera resolutions are 1 m in panchromatic scene and 4 m in multi-spectral imaging. This paper provides an initial geometric accuracy assessment of the KOMPSAT-2 high resolution image without ground control points and briefly introduces the sensor model of KOMPSAT-2. Also investigated and evaluated the obtained 3-dimensional terrain information using the MSC pass image and scene images acquired from the KOMPSAT-2 satellite.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.241-245
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• 2005

Strapdown inertial navigation system (SINS) integrated with astronavigation system (ANS) yields reliable mission capability and enhanced navigational accuracy for spacecrafts. The theory and characteristics of integrated system based on unscented Kalman filtering is investigated in this paper. This Kalman filter structure uses unscented transform to approximate the result of applying a specified nonlinear transformation to a given mean and covariance estimate. The filter implementation subsumed here is in a direct feedback mode. Axes misalignment angles of the SINS are observation to the filter. A simple approach for simulation of axes misalignment using stars observation is presented. The SINS error model required for the filtering algorithm is derived in space-stabilized mechanization. Simulation results of the integrated navigation system using a medium accuracy SINS demonstrates the validity of this method on improving the navigation system accuracy with the estimation and compensation for gyros drift, and the position and velocity errors that occur due to the axes misalignments.

• 한국항공우주학회지
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• 제41권4호
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• pp.319-326
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• 2013

본 논문에서는 다목적실용위성 3호의 초기 궤도운영 결과를 기술하였다. 다목적실용위성 3호는 2012년 5월 18일 발사된 이후 지상국 추적데이터 및 GPS 수신기 데이터를 이용한 궤도결정을 통해 위성의 초기 궤도정보를 획득하였다. 또한, 발사체 투입 궤도로부터 임무궤도로의 변경을 위한 궤도조정을 성공적으로 완료하였다. 그리고 GPS 수신기 원시데이터 및 IGS 데이터를 이용한 정밀궤도결정을 통해 궤도 정밀도를 확인하였다. 다목적 실용위성 3호는 현재 임무궤도에서 정상 운영 중에 있으며, 한국항공우주연구원 지상 관제국에서는 위성 임무 수행에 필요한 궤도 데이터를 매일 생성하여 배포하고 있다. 초기 운영 기간 동안 수행된 궤도운영 결과는 향후 다른 위성의 초기운영의 참고자료로 활용할 예정이다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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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.

• 항공우주시스템공학회지
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• 제16권5호
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• pp.49-56
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• 2022

S-STEP 은 관심 지역의 시한성 긴급 표적 및 군사적 이상 징후를 감시하기 위한 초소형 SAR 위성 임무로, 고도 510 km의 저궤도에 32 대의 위성군을 배치하여 관심 지역에 대해 평균 재방문 주기를 30 분 이하로 달성한다. S-STEP의 임무 운용 모드는 표준 모드, 관측 모드, 통신 모드, 궤도유지 모드 등으로 구분되며, 이에 따라 자세 기동 모드 역시 초기 각속도 안정화, 태양 지향, 목표지점 및 지상국 지향, 추력 방향 유지 등으로 세분화된다. 이 연구에서는 S-STEP 임무 운용 시나리오의 예비 설계 결과와 위성체의 특성을 바탕으로 초기 각속도 안정화 및 태양 지향 모드와 관측 궤도 운용 모드에서의 자세 성능을 분석하였다. 분석 결과, 할당된 시간 이내에 필요한 자세 제어를 완료하여 각 모드에서 요구되는 자세 제어 정확도를 달성함을 확인하였다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.464-466
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• 2004

Ranging and 2-way Doppler measurements are very essential source for orbit determination in LEOP (Launch and Early Operation). This paper shows ranging system features of 13M TT &C antenna and test results recently acquired with KOMPSAT-l. Ranging and 2-way Doppler measurements were compared with KOMPSAT-I GPS telemetry data. Through comparison, it was found that constant and accurate ranging measurements are available with 13M antenna system. Ranging and Doppler measurement function is expected to be used for KOMPSAT-1 and KOMPSAT-2.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 춘계학술대회 논문집
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• pp.543-548
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• 2002

Railroad has been one of major public transportations with the advantages of safety and schedule accuracy. However, the sustainable development will be the first principle in order to save the earth environment in the future, and the only transportation that satisfies it can continuously survive. Transportation has caused air pollution severely. Thus, the most environment-friendly means of transport should be chosen to maintain clean environment in the 21st century. Railroad is currently the best choice to fulfill the mission. But, the overall railroad technologies should be developed in consideration of clean environment to be a future leading transportation.