• Journal of Positioning, Navigation, and Timing
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• 제10권2호
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• pp.113-120
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• 2021

The Distance Measuring Equipment (DME) is a ground-based aircraft navigation system and is considered as an infrastructure that ensures resilient aircraft navigation capability during the event of a Global Navigation Satellite System (GNSS) outage. The main problem of DME as a GNSS back up is a poor positioning accuracy that often reaches over 100 m. In this paper, a novel approach of applying deep reinforcement learning to a DME pulse design is introduced to improve the DME distance measuring accuracy. This method is designed to develop multipath-resistant DME pulses that comply with current DME specifications. In the research, a Markov Decision Process (MDP) for DME pulse design is set using pulse shape requirements and a timing error. Based on the designed MDP, we created an Environment called PulseEnv, which allows the agent representing a DME pulse shape to explore continuous space using the Soft Actor Critical (SAC) reinforcement learning algorithm.

• 한국항공우주학회지
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• 제44권3호
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• pp.240-246
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• 2016

근래 우주 과학 및 연구의 가장 뜨거운 뉴스 또는 성과는 2013년 NASA의 화성 로버인 Curiosity, 2013년 중국의 달 착륙선/로버인 Chang'e 3 호, 2014년 ESA의 67P/Churyumov-Gerasimenko 소행성 탐사선 Rosetta, 그리고 2015년 NASA의 명왕성 탐사선 New Horizons 일 것이다. 이와 같은 장거리 심우주 탐사가 현 기술로 가능하다는 것에 매우 고무될 수밖에 없다. 하지만 이런 놀라운 심우주 항행 기술의 발전에도 불구하고 심우주 데이터 통신 기술 영역은 이렇다 할 변화가 없었다. 이 영역은 큰 변화를 현재까지 거부해 왔으나 최근 들어 지상의 우수한 통신 기술들을 심우주 탐사에 적용하려는 움직임이 관찰되고 있음에 주목할 필요가 있다. 그중에 하나가 본 논문에서 다루려고 하는 태양계 인터넷 기술이다. 본 논문에서 심우주 탐사에 태양계 인터넷이 미치는 영향을 분석하여 발표하고자 한다.

• 우주기술과 응용
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• 제3권1호
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• pp.58-71
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• 2023

본 논문에서는 관성측정장치와 천측 항법을 활용한 수평 위치 추정을 위한 항법 시스템 설계에 대해 기술하였다. 우주 상에서 별은 천구 상에 널리 퍼져 있는 천체로서 별의 관측을 통해 자세 정보를 획득하는데 주로 사용되어 왔다. 하지만 별의 고도 정보를 통해 수평 위치에 대한 정보 또한 획득이 가능한데, 이는 천측 항법이라고 불리며 예전 항해사들이 바다 위 항해 중에 자기의 위치를 알아내던 원리와 동일하다. 특히 GPS 등의 사용이 불가능한 심우주에서는 비교적 관측이 쉬운 별을 통해 위치에 대한 정보를 획득하는 것이 중요하다. 따라서 본 논문에서는 수평 위치정보를 추정할 수 있는 항법 시스템을 소개하며 측정값을 활용하는 방식에 따라 약결합과 강결합의 두 가지 방식의 시스템을 설계하고자 한다. 시뮬레이션을 통해 설계된 시스템이 올바르게 수평 위치정보를 추정하는지 여부와 함께 약결합과 강결합 방식의 성능을 비교하여 추후 천측 항법을 활용한 항법 시스템 설계에 도움이 되고자 한다.

• 한국항공우주학회지
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• 제50권12호
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• pp.877-888
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• 2022

최근 루나 게이트웨이의 선구자 임무인 CAPSTONE이 NRHO에서 통신 및 항법 기술 시연을 위해 소형발사체로 발사됨에 따라 전용 소형발사체와 소형위성을 이용하여 심우주 임무를 가능하게 한 이번 행사가 큰 주목을 받았다. 본 연구에서는 소형발사체 이중발사 운영개념이 소개하고, 달, 화성 및 소행성 탐사를 위한 새로운 개념의 가능성을 검토했다. 단독발사로 달 저궤도 임무에 약 247 kg을, 이중발사로 화성 및 소행성 아포피스와 같은 목적지에 각각 215 kg 및 183 kg을 수송할 수 있는 것으로 나타났다.

• Journal of Astronomy and Space Sciences
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• 제34권2호
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• pp.139-151
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• 2017

This paper presents an overview of deep space orbit determination software (DSODS), as well as validation and verification results on its event prediction capabilities. DSODS was developed in the MATLAB object-oriented programming environment to support the Korea Pathfinder Lunar Orbiter (KPLO) mission. DSODS has three major capabilities: celestial event prediction for spacecraft, orbit determination with deep space network (DSN) tracking data, and DSN tracking data simulation. To achieve its functionality requirements, DSODS consists of four modules: orbit propagation (OP), event prediction (EP), data simulation (DS), and orbit determination (OD) modules. This paper explains the highest-level data flows between modules in event prediction, orbit determination, and tracking data simulation processes. Furthermore, to address the event prediction capability of DSODS, this paper introduces OP and EP modules. The role of the OP module is to handle time and coordinate system conversions, to propagate spacecraft trajectories, and to handle the ephemerides of spacecraft and celestial bodies. Currently, the OP module utilizes the General Mission Analysis Tool (GMAT) as a third-party software component for high-fidelity deep space propagation, as well as time and coordinate system conversions. The role of the EP module is to predict celestial events, including eclipses, and ground station visibilities, and this paper presents the functionality requirements of the EP module. The validation and verification results show that, for most cases, event prediction errors were less than 10 millisec when compared with flight proven mission analysis tools such as GMAT and Systems Tool Kit (STK). Thus, we conclude that DSODS is capable of predicting events for the KPLO in real mission applications.

• 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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• 제36권4호
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• pp.293-306
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• 2019

In this study, the observational arc-length effect on orbit determination (OD) for the Korea Pathfinder Lunar Orbiter (KPLO) in the Earth-Moon Transfer phase was investigated. For the OD, we employed a sequential estimation using the extended Kalman filter and a fixed-point smoother. The mission periods, comprised between the perigee maneuvers (PM) and the lunar orbit insertion (LOI) maneuver in a 3.5 phasing loop of the KPLO, was the primary target. The total period was divided into three phases: launch-PM1, PM1-PM3, and PM3-LOI. The Doppler and range data obtained from three tracking stations [included in the deep space network (DSN) and Korea Deep Space Antenna (KDSA)] were utilized for the OD. Six arc-length cases (24 hrs, 48 hrs, 60 hrs, 3 days, 4 days, and 5 days) were considered for the arc-length effect investigation. In order to evaluate the OD accuracy, we analyzed the position uncertainties, the precision of orbit overlaps, and the position differences between true and estimated trajectories. The maximum performance of 3-day OD approach was observed in the case of stable flight dynamics operations and robust navigation capability. This study provides a guideline for the flight dynamics operations of the KPLO in the trans-lunar phase.

• 한국전자통신학회논문지
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• 제8권1호
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• pp.27-40
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• 2013

본 연구는 미래예측방법으로 많이 활용되고 있는 시나리오플래닝 방법론을 적용하여 2006년에 개발된 한국형 수중로봇시스템(심해무인잠수정시스템)의 바람직한 미래상을 도출하였다. 한국이 개발한 이 심해무인잠수정의 설계심도는 6000미터이며, 그 구성을 보면, '해미래'는 실질적인 심해탐사작업을 실행하고, 이 '해미래'를 지원하는 '해누비'는 심해에서 시료채취나 탐사가 가능하다. 한편 이 한국형 심해무인잠수정시스템은 수중복합항법시스템을 사용하고 있지만, 6000m심해에서 5m이내의 항법오차가 있고 50cm이내의 상대 위치오차를 가지고 있다. 따라서 본고는 이를 보완하여 관련 분야에서 기술 선도국이 될 수 있는 한국정부가 추진해야 할 바람직한 미래전략방향을 고찰했다. 그 결과 인디케이터와 가상벽을 갖춘 외부장치를 구비한 심해무인잠수정 시스템 개발이 한국에 있어 미래지향적인 정책추진방안이었다.

• International Journal of Advanced Culture Technology
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• 제9권4호
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• pp.302-306
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• 2021

Indoor localization is one of the basic elements of Location-Based Service, such as indoor navigation, location-based precision marketing, spatial recognition of robotics, augmented reality, and mixed reality. We propose a Voxel Labeling-based visual positioning system using object simultaneous localization and mapping (SLAM). Our method is a method of determining a location through single image 3D cuboid object detection and object SLAM for indoor navigation, then mapping to create an indoor map, addressing it with voxels, and matching with a defined space. First, high-quality cuboids are created from sampling 2D bounding boxes and vanishing points for single image object detection. And after jointly optimizing the poses of cameras, objects, and points, it is a Visual Positioning System (VPS) through matching with the pose information of the object in the voxel database. Our method provided the spatial information needed to the user with improved location accuracy and direction estimation.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2023년도 추계학술발표대회
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• pp.624-627
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• 2023

Unmanned aerial vehicles are gaining in popularity with the development of science and technology, and are being used for a wide range of purposes, including surveillance, rescue, delivery of goods, and data collection. In particular, the ability to avoid obstacles during navigation without human oversight is one of the essential capabilities that a drone must possess. Many works currently have solved this problem by implementing deep reinforcement learning (DRL) model. The essential core of a DRL model is reward function. Therefore, this paper proposes a new reward function with appropriate action space and employs dueling double deep Q-Networks to train a drone to navigate in indoor environment without collision.