• 한국군사과학기술학회지
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• 제21권6호
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• pp.744-751
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• 2018

In this paper, we propose a fast detection and identification algorithm of chemical gases with a passive FTIR spectrometer. We use a pre-detection algorithm that can reduce the spatial region effectively for gas detection and the candidates of the target. It is possible to remove background spectra effectively from measured spectra with the least-squares method. The CC(Correlation Coefficients) and the SNR(Signal-to-Noise Ratio) methods are used for the detection of target gases. The proposed pre-detection algorithm allows the total process of chemical gas detection to be performed with lower complexity compared with the conventional algorithms. This paper can help developing real-time chemical detection instruments and various applications of FTIR spectrometers.

• 한국전자파학회논문지
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• 제23권9호
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• pp.1107-1115
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• 2012

본 논문은 수면에서 복사되는 마이크로파 대역의 미약한 열잡음 전파를 수신하여 수면 온도의 변화를 실시간 원격으로 모니터링할 수 있는 마이크로파 라디오미터의 개발에 관한 연구 내용을 소개한다. 수면 온도의 원격 측정 범위 $5{\sim}30^{\circ}C$, 최대 오차 $2^{\circ}C$의 성능을 달성하는 데 요구되는 마이크로파 라디오미터의 설계 사양을 도출하였으며, 도출된 사양을 만족시키기 위한 라디오미터 수신기를 설계, 제작하였다. 성능 측정 결과, 제작된 수신기는 주파수 5.02 GHz, 대역폭 50 MHz, 45.2 dB의 시스템 이득과 수신 감도 0.56 K 이내로 설계 목표 사양을 만족하였다. 제작된 수신기와 표준 혼 안테나로 구성된 마이크로파 라디오미터로 간이 풀장을 이용 $7.5{\sim}18^{\circ}C$ 범위의 수면 온도 변화에 대한 원격 측정 실험 결과, 오차 $0.45^{\circ}C$ 이하의 수면 온도 측정 성능을 확인할 수 있었다.

• Journal of the Optical Society of Korea
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• 제20권6호
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• pp.669-677
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• 2016

A miniaturized FTIR spectrometer based on lamellar grating interferometry is being developed for passive remote-sensing. Consisting of a pair of micro-mirror arrays, the lamellar grating can be fabricated using MEMS technology. This paper describes a method to compute the optical field in the interferometer to optimize the design parameters of the lamellar grating FTIR spectrometer. The lower limit of the micro-mirror width in the grating is related to the formation of a Talbot image in the near field and is estimated to be about $100{\mu}m$ for the spectrometer to be used for the wavelength range of $7-14{\mu}m$. In calculating the far field at the detection window, the conventional Fraunhofer equation is inadequate for detection distance of our application, misleading the upper limit of the micro-mirror width to avoid interference from higher order diffractions. Instead, the far field is described by the unperturbed plane-wave combined with the boundary diffraction wave. As a result, the interference from the higher order diffractions turns out to be negligible as the micro-mirror width increases. Therefore, the upper limit of the micro-mirror width does not need to be set. Under this scheme, the interferometer patterns and their FT spectra are successfully generated.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2002년도 Proceedings of International Symposium on Remote Sensing
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• pp.604-609
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• 2002

The passive microwave remote sensing has progressed considerably in recent years. Important earth surface parameters are detected and monitored by airborne and space born radiometers. However the spatial resolution of real aperture measurements is constrained by the antenna aperture size available on orbiting platforms and on the ground. The inverse problem technique is researched in order to improve the spatial resolution of microwave scanning radiometer. We solve a two-dimensional (surface) temperature-imaging problem with a major intention to develop high-resolution methods. In this paper, the scenario for estimation of both radiometer point spread function (PSF) and target configuration is explained. The PSF of the radiometer is assumed to be unknown and estimated from the observations. The configuration and brightness temperature of targets are also estimated. To do this, we deal with the parametric modeling of observation scenario. The performance of developed algorithms is illustrated on two-dimensional experimental data obtained by the water vapor radiometer.

• 한국해양공학회지
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• 제34권5호
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• pp.371-376
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• 2020

Underwater acoustics, which is the study of the phenomena related to sound waves in water, has been applied mainly in research on the use of sound navigation and range (SONAR) systems for communication, target detection, investigation of marine resources and environments, and noise measurement and analysis. Underwater acoustics is mainly applied in the field of remote sensing, wherein information on a target object is acquired indirectly from acoustic data. Presently, machine learning, which has recently been applied successfully in a variety of research fields, is being utilized extensively in remote sensing to obtain and extract information. In the earlier parts of this work, we examined the research trends involving the machine learning techniques and theories that are mainly used in underwater acoustics, as well as their applications in active/passive SONAR systems (Yang et al., 2020a; Yang et al., 2020b; Yang et al., 2020c). As a follow-up, this paper reviews machine learning applications for the inversion of ocean parameters such as sound speed profiles and sediment geoacoustic parameters.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.474-477
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• 2005

In tactical theater, it is crucial to detect ground moving targets and to locate them precisely. This problem can be resolved by using SAR (Synthetic Aperture Radar) sensors providing GMTI (Ground Moving Target Indication) capability. In general, to implement a robust GMTI sensor is not simple because of the strong competitions between target signals and clutter signals on the ground, and low speed of moving targets. Contrary to the case that a delay canceller is mostly suitable for ground surveillance radars, DPCA (Displaced Phase Centered Antenna) or STAP (Space Time Adaptive Processing) techniques have been adapted for GMT! function of modem airborne radars. In this paper, anew scheme of DPCA using two passive antennas with vertical separation is proposed, which also provides good clutter cancellation performance. The proposed scheme enables us to scan straight ahead of the carrying platform that is impossible with typical DPCA configuration. Simulations using various conditions have been performed to validate the proposed scheme, and the results are acceptable.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.378-381
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• 2007

Analyses of Tropical Rainfall Measuring Mission (TRMM) microwave radiometer (TMI) and precipitation radar (PR) data show that the rainfall inhomogeneity, represented by the coefficient of variation, decreases as rain rate increases at the low resolution (the footprint size of TMI 10 GHz channel). The rainfall inhomogeneity, however, is relatively constant for all rain rates at the high resolution (the footprint size of TMI 37 GHz channel). Consequently, radiometric signatures at lower spatial resolutions are characterized by larger dynamic range and smaller variability than those at higher spatial resolution. Based on the observed characteristics, this study develops a low-resolution (${\sim}40{\times}40$ km) rainfall retrieval algorithm utilizing realistic rainfall distributions in the a-priori databases. The purpose of the low-resolution rainfall algorithm is to make more reliable climatological rainfalls from various microwave sensors, including low-resolution radiometers.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.649-652
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• 2005

In this paper we present a detail approach of the determination of IFOV (Instantaneous Field of View) of high-resolution (l m) panchromatic satellite image over test site. IFOV is the representative measurements as the determination of the spatial resolution in remote sensed imaging system. It can be defined as some area on the ground with the particular altitude when the satellite acquires the image at any given time. Especially, spatial resolution of passive sensors primarily depends on their IFOV. The determination of IFOV goes through simple steps of procedure as followings: Firstly, the GSD (Ground Sample Distance) should be computed at each point on the geometrically corrected image. Then, The GSD is converted into the IFOV. So we are going to explain our test procedures and results.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 1998년도 Proceedings of International Symposium on Remote Sensing
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• pp.138-148
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• 1998

The aim of the work described in this paper is to develop a complex underground acoustic system which detects and localizes the origin of an underground hammering sound using an array of hydrophones located about loom underground. Three different methods for the sound localization will be presented, a time-delay method, a power-attenuation method and a hybrid method. In the time-delay method, the cross correlation of the signals received from the way of sensors is used to calculate the time delays between those signals. In the power-attenuation method, the powers of the received signals provide a measure of the distances of the source from the sensors. A new hybrid method has been developed for estimating the origin of the underground acoustic source by coupling both methods. The Nelder-Meade simplex search algorithm is then used to numerically estimate the position of the source in those methods. For each method the sound localization is carried out in three dimensions underground. The distance between the true and estimated origins of the source is in some cases less than 6m for a search area of radius 250m.

• 대한원격탐사학회지
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• 제39권6_1호
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• pp.1185-1193
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• 2023

위성 영상을 활용하여 정확한 토양 수분도를 산정하는 연구는 원격탐사 응용 분야에 포함되는 중요한 기본 연구 주제 중 하나이다. 이 연구의 목적은 KOMPSAT-3/3A 영상과 KOMPSAT-5 SAR 영상을 적용하여 시험 지역에 대하여 토양수분도를 제작하고 산정된 결과를 정확도 검증 차원에서 미국 NASA에서 제공하는 Soil Moisture Active Passive (SMAP)의 토양수분 자료와 정량 비교하는 것이다. 한편 농림 식생 지대를 중심으로 토양수분도를 산정하기 위하여 환경공간정보서비스에서 제공하는 토지피복지도를 연구에 적용하였다. 시험 연구 지역은 이 연구에 적용한 수분 구름 모델(Water Cloud Model)에 기반한 토양수분 산정 알고리즘 적용에 필요한 입력 자료가 모두 가용한 제주 서부 지역을 선정하였다. 토양수분도 제작에 사용한 Synthetic Aperture Radar (SAR) 영상은 KOMPSAT-5 HV와 Sentinel-1 VV 영상이며, 식생지수는 KOMPSAT-3 영상의 지표반사도를 사용하였다. 이 연구에서 산출한 토양수분도 산정 결과와 SMAP (L-3) 자료를 차분 연산으로 비교하면 차이 값이 평균 4.13±3.60p%의 높은 일치도를 보이는 것으로 나타났고, SMAP (L-4) 자료와의 차분 연산 결과는 평균 14.24±2.10p% 수준의 일치도를 보였다. 이 연구를 통하여 향후 우리나라 위성영상과 공공 제공자료를 이용하여 정확도가 높은 정밀 토양수분도를 제작할 수 있는 가능성을 제시하였다.