• Korean Journal of Remote Sensing
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• v.39 no.6_2
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• pp.1529-1539
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• 2023

The data from Geostationary Ocean Color Imager-II (GOCI-II), which observes the color of the sea to monitor marine environments, undergoes various correction processes in the ground station system, producing data from Raw to Level-2 (L2). Quality issues arising at each processing stage accumulate step by step, leading to an amplification of errors in the satellite data. To address this, improvements were made to the GOCI-II ground station system to measure potential optical quality and geolocation accuracy errors in the Level-1A/B (L1A/B) data. A newly established Radiometric and Geometric Performance Assessment Module (RGPAM) now measures five optical quality factors and four geolocation accuracy factors in near real-time. Testing with GOCI-II data has shown that RGPAM's functions, including data processing, display and download of measurement results, work well. The performance metrics obtained through RGPAM are expected to serve as foundational data for real-time radiometric correction model enhancements, assessment of L1 data quality consistency, and the development of reprocessing strategies to address identified issues related to the GOCI-II detector's sensitivity degradation.

• Journal of Space Technology and Applications
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• v.4 no.1
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• pp.74-85
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• 2024

As the limitations of conventional radio communications between satellites and the ground become apparent, various experiments are being conducted around the world to overcome them with space laser communication. In this study, we address the development of our own optical communications terminal (OCT) and optical ground station (OGS) and the experiments of free-space optical communication (FSOC) using them. Using a 30 mm-diameter OCT and a 250 mm-diameter portable OGS telescope, as well as commercial 10 Gbps SFP+ modules and media converters, we successfully transmitted and received 4K high-definition multimedia interface (HDMI) signals through 1,550 nm optical laser beam. The transmission and reception distances of the experiment were 3, 9, and 20 km, respectively, and the received signal strength at each distance was +6.1, -2.8, and -10.9 dBm, respectively. It was demonstrated that the 4K HDMI video lasted for over 10 minutes.

• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.34-40
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• 2024

Satellite images from Earth-orbit satellites are widely utilized in both the public sector and commercial industry. To achieve a high-quality satellite image service, satellite operation focuses on accurately transmitting images and information of space to users. In particular, the delivery time from ground system to user is the core factor of the quality of a ground station service. Thus, much development is underway to specifically shorten the time required for distribution to users. In this paper, we introduce an interface design of a ground station to shorten the delivery time from order to distribution, related to the archiving order of satellite images.

• Electronics and Telecommunications Trends
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• v.38 no.2
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• pp.85-95
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• 2023

Space optical communication technology capable of large-capacity, high-speed, and low-latency communication can reduce the size, weight, and power consumption of radio frequency communications in existing satellite systems, thereby reducing launch costs, accommodating additional science instruments, and extending lifetime. Despite the high technical difficulty, various projects are being carried out in advanced countries regarding space technology for use in national security and defense, earth observation, and space communications. We review the advantages, key components, and development trends of space optical communication technology, which is attracting attention in applications such as satellite communications, intersatellite linking, and deep space communications.

• Korean Journal of Optics and Photonics
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• v.33 no.3
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• pp.113-121
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• 2022

We analyze the link availability of satellite-to-ground free-space optical (FSO) communication systems in South Korea. Using ten-year meteorological data for five major cities (Seoul, Busan, Daegu, Daejeon, and Gwangju), we theoretically predict the link availability from the power losses induced by absorption, scattering, aerosols, and scintillation in the atmospheric channel. For accurate but conservative estimation of the link availability determined by cloud cover, we propose a loss model based on the maximum value of cloud droplet concentration. The results show that the link availability ranges from 45% to 70% when a single ground station is placed in a major city in South Korea and a 20-dB link budget is allocated for atmospheric loss. However, the availabilities improve to 90% and 97% when 3- and 5-site diversities are employed, respectively.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.671-680
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• 2021

This paper deals with the contents of designing and producing reconnaissance hardware and software, and verifying the functions after being installed on the CanSat platform and ground stations. The main reconnaissance mission is largely composed of two things: terrain search that renders the surrounding terrain in 3D using radar, GPS, and IMU sensors, and real-time detection of major objects through optical camera image analysis. In addition, data analysis efficiency was improved through GUI software to enhance the completeness of the CanSat system. Specifically, software that can check terrain information and object detection information in real time at the ground station was produced, and mission failure was prevented through abnormal packet exception processing and system initialization functions. Communication through LTE and AWS server was used as the main channel, and ZigBee was used as the auxiliary channel. The completed CanSat was tested for air fall using a rocket launch method and a drone mount method. In experimental results, the terrain search and object detection performance was excellent, and all the results were processed in real-time and then successfully displayed on the ground station software.

• The Optical Journal
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• s.110
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• pp.44-52
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• 2007

아시아를 대표하는 국제 규모의 디지털 이미징 전시회인 '2007 서울국제사진영상기자재전/디지털영상전' 이 지난 5월 17일부터 20일까지 나흘간의 일정으로 코엑스 본관 1층 태평양홀에서 성대하게 개최됐다. 금년에 16회째를 맞이한 이 전시회에는 19개 국에서 175여 개 사(570여개 부스)가 참가하여 급속한 변화와 성장을 거듭하고 있는 다양한 디지털 사진 영상장비를 선보였다. 특히 삼성테크윈을 비롯하여 카메라 메이저 업체들이 대거 참가하여 포토쇼의 '꽃' 이라고 할 수 있는 디지털 카메라를 선보이고 다양한 체험 이벤트를 벌여 전시회 분위기를 한껏 고조시켰다. 전시기간동안 수많은 전문.취미 사진가들을 비롯하여 세계 각국의 바이어들까지 총 6만여 명의 참관객들이 전시장을 찾아 사진영상분야에 대한 뜨거운 관심과 호응도를 확인할 수 있는 계기가 되었다.

• Korean Journal of Remote Sensing
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• v.14 no.3
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• pp.213-222
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• 1998

Electro-Optical Camera(EOC) is the main payload of the KOrea Multi-Purpose SATellite(KOMPSAT) with the mission of cartography to build up a digital map of Korean territory including a Digital Terrain Elevation Map(DTEM). This instalment which comprises EOC Sensor Assembly and EOC Electronics Assembly produces the panchromatic images of 6.6 m GSD with a swath wider than 17 km by push-broom scanning and spacecraft body pointing in a visible range of wavelength, 510~730 nm. The high resolution panchromatic image is to be collected for 2 minutes during 98 minutes of orbit cycle covering about 800 km along ground track, over the mission lifetime of 3 years with the functions of programmable gain/offset and on-board image data storage. The image of 8 bit digitization, which is collected by a full reflective type F8.3 triplet without obscuration, is to be transmitted to Ground Station at a rate less than 25 Mbps. EOC was elaborated to have the performance which meets or surpasses its requirements of design phase. The spectral response, the modulation transfer function, and the uniformity of all the 2592 pixel of CCD of EOC are illustrated as they were measured for the convenience of end-user. The spectral response was measured with respect to each gain setup of EOC and this is expected to give the capability of generating more accurate panchromatic image to the users of EOC data. The modulation transfer function of EOC was measured as greater than 16 % at Nyquist frequency over the entire field of view, which exceeds its requirement of larger than 10 %. The uniformity that shows the relative response of each pixel of CCD was measured at every pixel of the Focal Plane Array of EOC and is illustrated for the data processing.

• Proceedings of the Korea Technology Innovation Society Conference
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• 2017.05a
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• pp.71-79
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• 2017

조종사가 탑승하지 않고도 지정된 임무를 수행할 수 있도록 제작된 무인항공기(드론)가 다양한 장비(광학, 적외선, 레이더 센서 등)를 탑재하여 활용되고 있다. 지금까지는 국가안보 유지 수단으로서 감시 정찰 정밀공격무기의 유도 등의 임무를 수행하여 왔다. 최근에는 민간부문에서도 다양한 용도로 활용되고 있어서 정부(국토교통부 산업통상자원부)는 무인항공기의 국내경제발전의 파급효과를 인지하고, 세계 무인항공기시장에서 우선순위를 선점하기 위해 투자확대를 기해 왔다. 무인항공기시장이 산업발전과 고용촉진에 도움이 되어 국내경제에 긍정적인 효과가 많다고 하더라도 무인항공기의 안전운행을 담보할 다양한 법적 제도적인 장치의 마련이 필요하다. 따라서 무인항공기로 야기되는 다양한 유형의 사고를 검토하여 이에 대한 법적 책임에 대한 분석이 필요하다. 무인항공기의 사고는 운영자의 운영상의 과실로 인한 사고도 있고 무인항공기 자체의 결함으로 인한 사고도 발생할 수 있다. 또한 운행자의 고의과실로 인한 타인의 권리(프라이버시권 등)를 침해하는 경우나 무인항공기끼리의 충돌사고도 발생할 수 있다. 이러한 사고로 인한 책임은 민사책임으로서 대부분 지상 제3자에 대한 생명 신체 또는 재산상의 손해배상책임이다. 이러한 책임을 규율하는 국제협약으로 로마협약이 있지만 체약국이 없기 때문에 국제협약으로서의 역할을 못하고 있다. 따라서 현재로서는 각국의 국내법에 의하여 해결될 가능성이 많을 것으로 생각된다. 무인항공기 운영자의 과실로 인한 사고는 민법이나 상법이 적용될 수 있고, 무인항공기의 제작결함으로 인해 사고가 발생하였을 경우와 시스템의 오작동으로 인해 사고가 발생하였다면 제조물 책임을 물어야 할 경우도 있을 수 있다. 이러한 법적 쟁점에 대한 검토를 통하여 무인항공기 공급과 활용의 확대로 인한 다양한 사고발생과 책임범위를 명확히 하여 사고당사자들의 책임관계를 인식시키는 것이 필요하다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.9
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• pp.784-793
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• 2017

A two-axis gimbal-type X-band antenna mounted on an observation satellite can efficiently transmit high-capacity image data to a ground station regardless of both the satellite position and the orbital motion. However, this X-band antenna induces unnecessary micro-jitter which can degrade the image quality of the high-resolution observation satellite. Therefore, to achieve the high-resolution image quality from the observation satellite, micro-jitters have been required to be isolated. In this study, to resolve aforementioned drawback, we proposed blade gear using a shape memory alloy (SMA) applied to azimuth stage of X-band antenna. To investigate the rotational basic characteristics of the proposed SMA blade gear, we performed rotational static loading test. Futhermore, to evaluate the cycle to failure of the gear, accelerated life test was conducted. The temperature test was conducted to confirm rotational basic characteristics at various temperature conditions. To verify the isolation performance for micro-jitter, we performed micro-jitter measurement test.