Ka Band Antenna Development for COMS

ABSTRACTThis article presents a geostatistical approach for downscaling precipitation products from passive microwave satellites with geostationary Meteorological Satellite observations. More precisely, the Advanced Microwave Scanning Radiometer 2 (AMSR2) precipitation (daily level 3 product) with 0.25° spatial resolution and the Communication, Ocean and Meteorological Satellite (COMS) infrared (IR) data with 5 km spatial resolution were used for the downscaling experiment over the Korean peninsula. Brightness temperature data observed at COMS IR 1 and water vapour channels were incorporated for downscaling via area-to-point residual Kriging with non-linear regression. The evaluation results with densely sampled Automatic Weather Station data revealed that incorporating the COMS IR observations with the AMSR2 precipitation showed similar error statistics to those of the AMSR2 precipitation because of the limitations of IR observations themselves and the inherent errors of the AMSR2 precipitation product over land. However, the area-based evaluation using information entropy indicated that incorporating the COMS observations resulted in more detailed spatial variation in the final product than direct downscaling of the AMSR2 precipitation. In addition, local precipitation patterns could be captured when there were regions with missing precipitation values in the AMSR2 product. Consequently, the downscaling result is useful for understanding the local precipitation patterns with an accuracy similar to that provided by microwave satellite observations. It is also suggested that the spatial variability in the downscaling result and errors in input low-resolution data should be considered when downscaling coarse resolution data using fine resolution auxiliary variables.

This paper presents an Image Motion Compensation (IMC) algorithm for Korea's Communication, Ocean, and Meteorological Satellite (COMS). An IMC algorithm is a priority component of the Image Navigation and Registration (INR) system to locate and register radiometric image data. To eliminate image distortions, depointing of the imager aiming direction must be adjusted. A compensation algorithm to correct depointing caused by satellite motion is designed, and the capability of the algorithm is compared with that of existing algorithm applied to the GOES's INR system. The algorithm developed in this paper improves pointing accuracy by efficiently compensating for depointing of the imager aiming direction. I. Introduction

Evaluation of geostationary satellite (COMS) based Priestley–Taylor evapotranspiration

The power capacity of solar photovoltaics (PVs) in Korea has grown dramatically in recent years, and an accurate estimation of solar resources is crucial for the efficient management of these solar PV systems. Since the number of solar irradiance measurement sites is insufficient for Korea, satellite images can be useful sources for estimating solar irradiance over a wide area of Korea. In this study, an artificial neural network (ANN) model was constructed to calculate hourly global horizontal solar irradiance (GHI) from Korea Communication, Ocean and Meteorological Satellite (COMS) Meteorological Imager (MI) images. Solar position variables and five COMS MI channels were used as inputs for the ANN model. The basic ANN model was determined to have a window size of five for the input satellite images and two hidden layers, with 30 nodes on each hidden layer. After these ANN parameters were determined, the temporal and spatial applicability of the ANN model for solar irradiance mapping was validated. The final ANN ensemble model, which calculated the hourly GHI from 10 independent ANN models, exhibited a correlation coefficient (R) of 0.975 and root mean square error (RMSE) of 54.44 W/m² (12.93%), which were better results than for other remote-sensing based works for Korea. Finally, GHI maps for Korea were generated using the final ANN ensemble model. This COMS-based ANN model can contribute to the efficient estimation of solar resources and the improvement of the operational efficiency of solar PV systems for Korea.

COMS (Communication, Ocean and Meteorological Satellite) named Chunrian is aimed to develop domestic space proven technology of Ka-band switching transponder and multi-beam antenna technologies, and to exploit advanced multimedia communication services. This paper is purposed to study development design, manufacturing and test technology of Ka-band payload system, and to verify outstanding technology level through ETRI project.

Tropical cyclones (TCs) are among the most severe and destructive natural events, and they have a major detrimental impact on both the economy and society. This study used Geo-KOMPSAT-2A (GK2A) satellite data to estimate TC intensity in the western North Pacific based on a convolutional neural network (CNN) model. Given that the GK2A data cover only the period since 2019, we applied transfer learning to the model using information learned from previous Communication, Ocean, and Meteorological Satellite (COMS) data, which cover a considerably longer period (2011–2019). Transfer learning is a powerful technique that can improve the performance of a model even if the target task is based on a small amount of data. Experiments with various transfer learning methods using the GK2A and COMS data showed that the frozen–fine-tuning method had the best performance due to the high similarity between the two datasets. The test results for 2021 showed that employing transfer learning led to a 20% reduction in the root mean square error (RMSE) compared to models using only GK2A data. For the operational model, which additionally used TC images and intensities from six hours earlier, transfer learning reduced the RMSE by 5.5%. Because continuous long-term data are not always available for TC intensity estimation based on geostationary satellite images, these results imply that transfer learning may constitute a new advance in this area. Acknowledgement. This research was supported by Korea Institute of Marine Science & Technology Promotion (KIMST) funded by the Korea Coast Guard (RS-2023-00238652, Integrated Satellite-based Applications Development for Korea Coast Guard).  

Despite the same purpose, each satellite product has different value because of its inescapable uncertainty. Also the satellite products have been calculated for a long time, and the kinds of the products are various and enormous. So the efforts for reducing the uncertainty and dealing with enormous data will be necessary. In this paper, we create an ensemble Sea Surface Temperature (SST) using MODIS Aqua, MODIS Terra and COMS (Communication Ocean and Meteorological Satellite). We used Bayesian Model Averaging (BMA) as ensemble method. The principle of the BMA is synthesizing the conditional probability density function (PDF) using posterior probability as weight. The posterior probability is estimated using EM algorithm. The BMA PDF is obtained by weighted average. As the result, the ensemble SST showed the lowest RMSE and MAE, which proves the applicability of BMA for satellite data ensemble. As future work, parallel processing techniques using Hadoop framework will be adopted for more efficient computation of very big satellite data.

Ground-truthing is a major problem in the satellite estimation of rain rate. This problem is that the measurement taken by the satellite sensor is fundamentally different from the one it is compared with on the ground. Additionally, since the satellite has the limited capability to measure the light rain rate exactly, the comparison should also consider the threshold value of satellite rain rate. This paper proposes a ground-truth design with threshold for the satellite rain rate. This ground-truth design is the generalization of the conventional ground-truth design which considered the only (zero, nonzero) and (nonzero, nonzero) measurement pairs. The mean-square error is used as an index of accuracy in estimating the ground measurement by satellite measurement. An application to the artificial random field shows that the proposed ground-truth design with threshold is valid as the design bias is zero. The same result is also derived in the application to the COMS (Communication, Ocean, and Meteorological Satellite) rain rate data in Korea.

COMS(Communication, Ocean and Meteorological Satellite), the first Korean geostationary meteorological satellite, provides free meteorological information through HRIT/LRIT(High/Low Rate Information Transmission) service. This work presents the development of data receiver circuit that is essential to the implementation of a low-cost meteorological information receiver system. The data receiver circuit processes the data units according to the specification of physical layer and data link layer of HRIT/LRIT service. For this purpose, the circuit consists of a Viterbi decoder, a sync. word detector, a derandomizer, a Reed-Solomon decoder and so on. The circuit also supports PCI express interface to pass the information data on to the host PC. The circuit was implemented on an FPGA(field programmable gate array) and its function was verified through simulations and hardware implementation.

Automation of the key flight dynamics operations for the geostationary orbit satellite mission is analyzed and designed. The automation includes satellite orbit determination, orbit prediction, event prediction, and fuel accounting. An object-oriented analysis and design methodology is used for design of the automation system. Automation scenarios are investigated first and then the scenarios are allocated to use cases. Sequences of the use cases are diagramed. Then software components and graphical user interfaces are designed for automation. The automation will be applied to the Communication, Ocean, and Meteorology Satellite (COMS) flight dynamics system for daily routine operations.

Abstract. The Geostationary Ocean Color Imager (GOCI) onboard the Communication, Ocean, and Meteorological Satellite (COMS) is the first multi-channel ocean color imager in geostationary orbit. Hourly GOCI top-of-atmosphere radiance has been available for the retrieval of aerosol optical properties over East Asia since March 2011. This study presents improvements made to the GOCI Yonsei Aerosol Retrieval (YAER) algorithm together with validation results during the Distributed Regional Aerosol Gridded Observation Networks – Northeast Asia 2012 campaign (DRAGON-NE Asia 2012 campaign). The evaluation during the spring season over East Asia is important because of high aerosol concentrations and diverse types of Asian dust and haze. Optical properties of aerosol are retrieved from the GOCI YAER algorithm including aerosol optical depth (AOD) at 550 nm, fine-mode fraction (FMF) at 550 nm, single-scattering albedo (SSA) at 440 nm, Ångström exponent (AE) between 440 and 860 nm, and aerosol type. The aerosol models are created based on a global analysis of the Aerosol Robotic Networks (AERONET) inversion data, and covers a broad range of size distribution and absorptivity, including nonspherical dust properties. The Cox–Munk ocean bidirectional reflectance distribution function (BRDF) model is used over ocean, and an improved minimum reflectance technique is used over land. Because turbid water is persistent over the Yellow Sea, the land algorithm is used for such cases. The aerosol products are evaluated against AERONET observations and MODIS Collection 6 aerosol products retrieved from Dark Target (DT) and Deep Blue (DB) algorithms during the DRAGON-NE Asia 2012 campaign conducted from March to May 2012. Comparison of AOD from GOCI and AERONET resulted in a Pearson correlation coefficient of 0.881 and a linear regression equation with GOCI AOD = 1.083 × AERONET AOD − 0.042. The correlation between GOCI and MODIS AODs is higher over ocean than land. GOCI AOD shows better agreement with MODIS DB than MODIS DT. The other GOCI YAER products (AE, FMF, and SSA) show lower correlation with AERONET than AOD, but still show some skills for qualitative use.

Algorithm for retrieval of aerosol optical properties over the ocean from the Geostationary Ocean Color Imager

접촉 케플러 궤도요소로부터 변환된 NORAD TLE를 정지궤도 위성의 안테나 포인팅에 직접 사용하기 위한 분석을 수행하였다. 일주일에 한번씩 동서방향과 남북방향의 위치유지를 위한 궤도조정을 수행하고 하루에 두 번씩 추력기를 이용한 모멘텀 덤핑을 통해서 궤도가 계속 변하는 통신해양기상 위성에 대해서 변환된 NORAD TLE를 이용한 안테나 포인팅 오프셋 각을 계산하여 위성신호를 수신할 수 있는지 검토하였다. 이를 통해 변환된 NORAD TLE를 사용하여 위성 관제시스템의 안테나 포인팅에 관련된 인터페이스를 간단하게 수행할 수 있음을 보였다. 또한 이심률이 큰 천이궤도에 있어서 위성의 평균 근점각에 따른 변환된 NORAD TLE 값의 차이를 분석하여 천이궤도의 원지점 근처에서의 NORAD TLE 변환 값이 더 좋은 결과를 나타내는 것을 알 수 있었다. Antenna pointing analysis for a geostationary satellite has been performed for using the NORAD Two-Line-Elements (TLE) converted from osculating Keplerian orbital elements. In order to check the possibility of the reception of the satellite signal, the antenna offset angles have been derived for the Communications, Ocean, and Meteorological Satellite (COMS) which carries out weekly East-West and North-South station-keeping maneuvers and twice a day thruster assisted momentum dumping. Throughout the analysis, it is shown that the use of converted NORAD TLE simplifies the antenna pointing related interfaces in satellite mission control system. For a highly eccentric transfer orbit cases, further analysis presents that the converted NORAD TLE from near apogee gives more favorable results.

Exploring solar and wind energy resources in North Korea with COMS MI geostationary satellite data coupled with numerical weather prediction reanalysis variables

This paper deals with the design of an EBG antenna dedicated to feed a side front offset Cassegrain antenna (SFOCA) for a multibeam coverage of Europe in Ka band. Indeed, the EBG structure which permit to interlace equivalent radiating apertures, represents a new passive technology to realize multi beam coverage with only one reflector at an attractive cost compared to usual systems with beam forming networks or with several reflector antennas. The telecommunication mission studied requires on the one hand a multibeam reflector antenna with large F/D ratio to decrease the parasitic defocusing effects for high scanned beams and on the other hand, a circular polarization concept which reduces the price of the subscriber terminals assembly. These characteristics induce some focal structure specifications which cannot be reached with a classical EBG antenna. Also, the first step has been to improve the EBG antenna performances thanks to a more efficient feed which is a conical horn. The replacement of the patch by the horn permits to double the radiation bandwidth and to decrease the side lobes (-15 dB) of a 24 dB EBG antenna. The second job has been to reduce the parasitic interferences which occur in a multifeed EBG antenna especially that no polarization decoupling is achievable. Consequently, a multihorn two level EBG antenna with corrugations which permit to emplace the feeds outside the EBG cavity has been designed. As the performances of this structure are as well as those obtained with an EBG antenna fed by only one feed, we have study the whole system composed of the SFOCA and the multihorn two level EBG structure. The results obtained agree with the specifications because a EOC gain higher than 43 dB and sideslobes lower than -20 dB have been obtained for 90% of the beams. (7 pages)