• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.306-309
• /
• 2007

Japanese Ocean Flux Data Sets with Use of Remote Sensing Observations (J-OFURO) includes global ocean surface heat flux data derived from satellite data and are used in many studies related to air-sea interaction. Recently latent heat flux data version 2 was constructed in J-OFURO. In version 2 many points are improved compared with version 1. A bulk algorithm used for estimation of latent heat flux is changed from Kondo (1975) to COASRE 3.0(Fairall et al., 2005). In version 1 we used NCEP reanalysis data (Reynolds and Smith, 1994) as SST data. However, the temporal resolution of the data is weekly and considerably low. Recently there are many kinds of global SST data because we can obtain SST data using a microwave radiometer sensor such as TRMM/MI and Aqua/AMSR-E. Therefore, we compared many SST products and determined to use Merged satellite and in situ data Global Daily (MGD) SST provided by Japan Meteorological Agency. Since we use wind speed and specific humidity data derived from one DMSP/SSMI sensor in J-OFURO, we obtain two data at most one day. Therefore, there may be large sampling errors for the daily-mean value. In order to escape this problem, multi-satellite data are used in version 2. As a result we could improve temporal resolution from 3-days mean value in version 1 to daily-mean value in version 2. Also we used an Optimum Interpolation method to estimate wind speed and specific humidity data instead of a simple mean method. Finally the data period is extended to 1989-2004. In this presentation we will introduce latent heat flux data version 2 in J-OFURO and comparison results with other surface latent heat flux data such as GSSTF2 and HOAPS etc. Moreover, we will present validation results by using buoy data.

• 한국항공우주학회지
• /
• 제42권9호
• /
• pp.779-788
• /
• 2014

저궤도 위성이 제한된 전력 내에서 임무를 성공적으로 수행하기 위해서는 효율적인 전력생산이 중요하다. 이를 위해 저궤도 소형위성의 전력계에서는 주로 MPPT (Maximum Power Point Tracking) 방식을 사용하여 태양전지에서 생산되는 전력을 조절한다. 본 연구에서는 소형 큐브위성(KAUSAT-5)에 적용될 퍼지 로직 기반의 MPPT 알고리즘을 제안하며, 제안된 방법의 유용성을 확인하기 위해 MATLAB/Simulink와 STK (Systems Tool Kit)를 연동하여 시뮬레이션을 수행하였다. Simulink와 STK를 이용하여 위성 궤도와 자세에 따른 태양 광량과 운용모드에 따라 변하는 부하용량에 대해 KAUSAT-5의 두 가지 지향모드에서 EBA(Energy Balance Analysis)를 수행하였고, 이를 통해 제안된 퍼지 로직 기반의 MPPT 알고리즘의 성능을 확인하였다. 제안된 퍼지 로직 기반의 MPPT는 가장 일반적인 방법의 하나인 P&O (Perturbation & Observation)와 성능을 비교하여 유용성을 확인하였다.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2008년도 International Symposium on Remote Sensing
• /
• pp.155-158
• /
• 2008

The needs for digital models of real environment such as 3D terrain or cyber city model are increasing. Most of applications related with modeling and simulation require virtual environment constructed from geospatial information of real world in order to guarantee reliability and accuracy of the simulation. The most fundamental data for building virtual environment, terrain elevation and orthogonal imagery is acquired from optical sensor of satellite or airplane. Providing interoperable and reusable digital model is important to promote practical application of high-resolution satellite imagery. This paper presents the new research regarding representation of geospatial information, especially for 3D shape and appearance of virtual terrain, and describe framework for constructing real-time 3D model of large terrain based on high-resolution satellite imagery. It provides infrastructure of 3D simulation with geographical context. Details of standard-based approach for providing infrastructure of real-time 3D simulation using high-resolution satellite imagery are also presented. This work would facilitate interchange and interoperability across diverse systems and be usable by governments, industry scientists and general public.

• 항공우주시스템공학회지
• /
• 제13권3호
• /
• pp.23-31
• /
• 2019

현대의 위성들의 설계요구조건은 운용되는 목적에 따라 다양해진다. 기존 중/대형 위성과는 달리 저궤도에서 운용되는 소형위성의 경우 군사적인 목적을 나타내기도 한다. 그렇기 때문에 고해상도의 사진 및 영상 수요가 증가하며 다표적 관측이 중요하게 된다. 이에 다표적 관측을 하기 위해서 위성의 기동성은 중요한 설계변수이다. 기동성이 증가하기 위해서 소형화가 되면 전체 질량관성모멘트가 감소하기 때문에 위성의 강성을 높여야한다. 본체에 비해서 강성이 낮은 태양전지판의 경우 진동이 발생하기 때문에 영상획득에 큰 영향을 미친다. 이러한 진동특성을 확인하기 위하여 본 연구에서는 위성을 축소모델로 제작하여 자세기동을 모사하기 위한 실험 치구를 도입하였고, 위성의 강성을 모사하기 위한 모사장치를 제시하였다. 또한 실험방식은 스텝모터를 이용하여 와이어의 감는 길이에 따라 위성의 기동각을 모사하였으며, 기동실험 시 발생되는 위성의 본체 및 태양전지판에 대하여 진동특성을 실험적으로 검증하고자 한다.

• 한국항행학회논문지
• /
• 제16권6호
• /
• pp.900-909
• /
• 2012

저궤도 위성에 탑재하는 위성항법 수신기는 관측된 신호를 필터링하고 신호중단 시 궤도예측을 수행하는 항법필터를 장착하는데, 사용하는 위성동역학 모델이 필터성능을 주로 결정하게 된다. 본 연구에서는 항법필터에 필요한 정밀위성동역학 알고리듬을 연구하고 이를 계산하는 프로그램을 개발하였다. 정밀 중력가속도, 정밀좌표변환, 3체 중력, 대기저항, 태양복사압 모델을 결합하였으며, 해외 정밀궤도결정 프로그램을 이용하여 정확도를 검증하였다. 시뮬레이션과 실제 궤도 데이터를 사용하여 초기위치 정확도에 따른 궤도예측정확도를 분석 하였다. 개발된 모델은 위성탑재용 실시간 항법필터에 적용되는 동역학모델로는 충분한 정확도를 가지는 것을 확인하였다.

• 천문학회보
• /
• 제40권1호
• /
• pp.59.3-60
• /
• 2015

We investigate the clustering properties of Lyman-break galaxies (LBGs) at z ~ 4. Using the hierarchical galaxy formation model GALFORM, we predict the angular correlation function (ACF) of LBGs and compare this with the measured ACF from combined survey fields consisting of the Hubble eXtreme Deep Field (XDF) and CANDELS. We find that the predicted ACF is in a good agreement with the measured ACFs. However, when we divide the model LBGs into bright and faint subset, the predicted ACFs are less consistent with observations. We quantify the dependence of clustering on luminosity and show that the fraction of satellite LBGs is important for determining the amplitude of ACF at small scales. We find that central LBGs predominantly reside in ${\sim}10^{11}h^{-1}M_{solar}$ haloes and satellites reside in haloes of mass ${\sim}10^{12}-10^{13}h^{-1}M_{solar}$. The model predicts fewer bright satellite LBGs than is inferred from the observation. LBGs in the tails of the redshift distribution contribute significant additional clustering signal, especially on small scales. This spurious clustering may affect the interpretation of the halo occupation distribution, including the minimum halo mass and abundance of satellite LBGs.

• 전기학회논문지
• /
• 제62권11호
• /
• pp.1584-1589
• /
• 2013

A new and significantly small guided and resonant structure is suggested to take over bulky metallic hollow waveguides used in military satellite transceivers. Below Ku-band, the conventional waveguides resulting in quite heavy transceivers will be replaced by the low profile SIW(substrate integrated waveguide) structures that are distinguished from the others in that the suggested ones have much lower cut-off frequencies by the circuital configuration of DNG(dobule negative) constitutive parameters and become even smaller than the other SIWs. The design scheme is validated by the circuit and full-wave simulations from the guided, resonant, and coupled structures. Besides, a bandpass filter as the suggested coupled structure is fabricated with a cheap substrate in a low-budget fabrication process and its frequency response is measured as verification of the purpose of the design.

• Journal of Positioning, Navigation, and Timing
• /
• 제3권1호
• /
• pp.11-16
• /
• 2014

A Satellite Based Augmentation System (SBAS) is a representative differential GNSS system, which is used for the navigation performance improvement of Global Navigation Satellite System (GNSS) users. SBAS has been developed focusing on the securement of user integrity so that it can be used for the navigation in aviation fields. Accordingly, the development of SBAS has been completed, and it has been actively used in the United States, Europe, and Japan. As the new satellite of Global Positioning System (GPS) recently started to broadcast new civil signals (L5 frequency), the methods for improving user navigation performance in SBAS using this signal have also been studied. In Korea, to keep pace with these circumstances, full-scale SBAS development is expected to start in 2014, and studies on dual-frequency SBAS using L1/L5 frequencies will also be performed. In this study, before the full-scale development of dual-frequency SBAS in Korea, a simulation was performed to predict the performance and analyze the expected effects.

• 대한전자공학회:학술대회논문집
• /
• 대한전자공학회 2005년도 추계종합학술대회
• /
• pp.131-134
• /
• 2005

Recently, RF systems have rapidly grown with the extension of the mobile communication service The mobile service companies are providing the satellite broadcasting and common usage are expected. Coinciding with current trend, the development of improved satellite DMB (Digital Multimedia Broadcasting) tuner is required. To improve the receiving sensitivity under the poor communication circumstance, It is necessary to design the LNA (Low Noise Amplifier) with outstanding low noise characteristic and the BPF (Bandpass Filter) to transmit only desired signal without distortion and loss. Besides high reliability, the miniaturization and lightweight are required for design of mobile terminals. In this study, we designed and fabricated DMB SIR-type BPF which operates at 2642 MHz and is embedded in the substrate using LTCC. As a result, we obtained the passband insertion loss of 2.4 dB and the passband ripple of 0.08 dB. So this DMB SIR-type BPF is applicable to RF module of a satellite DMB tuner.

• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
• /
• pp.53-56
• /
• 2007

The Korean Geostationary satellite (COMS) to fly in year 2009 will carry a meteorological sensor from which visible channel measurements will be available. We developed a method utilizing satellite-derived BRDFs for the solar channel calibration over the bright desert area. The 6S model has been incorporated to account for directional effects of the surface using MODIS-derived BRDF parameters within the spectral interval in interest. Simulated radiances over the desert targets were compared with MODIS and SeaWiFS measured spectral radiances in order to examine the feasibility of the developed calibration algorithm. We also simulated TOA radiance over ocean targets to verify the consistency and reliability of the result. It was shown that simulated 16-day averaged radiances are in good agreement with the satellite-measured radiances within about ${\pm}5%$ uncertainty range for the year 2005, suggesting that the developed algorithm can be used for calibrating the COMS visible channel within about 5% uncertainty level.