296 research outputs found
ESTIMATION OF DATA MEMORY CAPACITY FOR CIRCULARLY POLARIZED SYNTHETIC APERTURE RADAR ONBOARD UNMANNED AERIAL VEHICLE PLATFORM (CP-SAR UAV)
Previously only linear polarization is widely used in the Synthetic Aperture Radar(SAR) system onboard spaceborne and airborne platforms. In such linearly polarized SAR(LP-SAR) systems, Faraday rotation in the ionosphere and platform posture will contribute tothe system noise. Therefore to improve this situation, currently a novel Circularly PolarizedSynthetic Aperture Radar (CP-SAR) sensor is developed in Microwave Remote SensingLaboratory, Chiba University. Moreover, from this research, a new backscattering data basedon circularly polarized wave in the remote sensing field can be obtained. As an early stage ofthe development of this CP-SAR sensor, we built an Unmanned Aerial Vehicle (UAV)platform for testing CP-SAR sensor capabilities. In this paper, we describe the novel CP-SARsensor and the method to design CP-SAR UAV especially in estimating the requirement ofdata memory capacity. Also a smaller antenna is possible to be implemented since the 3-dBaxial ratio on antenna characteristic becomes the main parameter in this new CP-SARtechnique. Hence, a compact CP-SAR sensor onboard a small and low cost spaceborneplatform yielding a high accuracy SAR image data can be realized in the near future
On the Equivalence of LEO-SAR Constellations and Complex High-Orbit SAR Systems for the Monitoring of Large-Scale Processes
High Earth orbit Synthetic Aperture Radar (SAR) systems offer high temporal sampling and moderate spatial resolution on a global scale, potentially outperforming conventional Low Earth Orbit (LEO) systems in revisit times. However, this requires complex system architectures such as burst operation
modes with multiple subswaths, large antennas, and digital beamforming. Similar temporal sampling and coverage enhancements can be realized with constellations of classical monostatic SAR instruments in LEO. This letter compares the complexity of such equivalent monostatic LEO-SAR constellations to complex high-altitude SAR systems and provides design numbers for two Medium Earth Orbit (MEO)-SAR mission examples and their LEO counterparts
Future exploration of Venus (post-Pioneer Venus 1978)
A comprehensive study was performed to determine the major scientific unknowns about the planet Venus to be expected in the post-Pioneer Venus 1978 time frame. Based on those results the desirability of future orbiters, atmospheric entry probes, balloons, and landers as vehicles to address the remaining scientific questions were studied. The recommended mission scenario includes a high resolution surface mapping radar orbiter mission for the 1981 launch opportunity, a multiple-lander mission for 1985 and either an atmospheric entry probe or balloon mission in 1988. All the proposed missions can be performed using proposed space shuttle upper stage boosters. Significant amounts of long-lead time supporting research and technology developments are required to be initiated in the near future to permit the recommended launch dates
小型衛星搭載の合成開口レーダー用の集中型送受信システムを有する2偏波対応進行波型アンテナ
学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 齋藤 宏文, 東京大学教授 橋本 樹明, 東京大学教授 保立 和夫, 東京電機大学教授 小林 岳彦, 東京工業大学教授 廣川 二郎University of Tokyo(東京大学
Statistical assessment on Non-cooperative Target Recognition using the Neyman-Pearson statistical test
Electromagnetic simulations of a X-target were performed in order to obtain its Radar Cross
Section (RCS) for several positions and frequencies. The software used is the CST MWS©. A 1 : 5
scale model of the proposed aircraft was created in CATIA© V5 R19 and imported directly into
the CST MWS© environment. Simulations on the X-band were made with a variable mesh size
due to a considerable wavelength variation. It is intended to evaluate the Neyman-Pearson (NP)
simple hypothesis test performance by analyzing its Receiver Operating Characteristics (ROCs)
for two different radar detection scenarios - a Radar Absorbent Material (RAM) coated model,
and a Perfect Electric Conductor (PEC) model for recognition purposes.
In parallel the radar range equation is used to estimate the maximum range detection for the
simulated RAM coated cases to compare their shielding effectiveness (SE) and its consequent
impact on recognition. The AN/APG-68(V)9’s airborne radar specifications were used to compute
these ranges and to simulate an airborne hostile interception for a Non-Cooperative Target
Recognition (NCTR) environment. Statistical results showed weak recognition performances
using the Neyman-Pearson (NP) statistical test. Nevertheless, good RCS reductions for most of
the simulated positions were obtained reflecting in a 50:9% maximum range detection gain for
the PAniCo RAM coating, abiding with experimental results taken from the reviewed literature.
The best SE was verified for the PAniCo and CFC-Fe RAMs.Simulações electromagnéticas do alvo foram realizadas de modo a obter a assinatura radar (RCS)
para várias posições e frequências. O software utilizado é o CST MWS©. O modelo proposto à
escala 1:5 foi modelado em CATIA© V5 R19 e importado diretamente para o ambiente de trabalho
CST MWS©. Foram efectuadas simulações na banda X com uma malha de tamanho variável
devido à considerável variação do comprimento de onda. Pretende-se avaliar estatisticamente
o teste de decisão simples de Neyman-Pearson (NP), analisando as Características de Operação
do Receptor (ROCs) para dois cenários de detecção distintos - um modelo revestido com material
absorvente (RAM), e outro sendo um condutor perfeito (PEC) para fins de detecção.
Em paralelo, a equação de alcance para radares foi usada para estimar o alcance máximo de
detecção para ambos os casos de modo a comparar a eficiência de blindagem electromagnética
(SE) entre os diferentes revestimentos. As especificações do radar AN/APG-68(V)9 do F-16 foram
usadas para calcular os alcances para cada material, simulando uma intercepção hostil num
ambiente de reconhecimento de alvos não-cooperativos (NCTR). Os resultados mostram performances
de detecção fracas usando o teste de decisão simples de Neyman-Pearson como detector
e uma boa redução de RCS para todas as posições na gama de frequências selecionada. Um ganho
de alcance de detecção máximo 50:9 % foi obtido para o RAM PAniCo, estando de acordo com
os resultados experimentais da bibliografia estudada. Já a melhor SE foi verificada para o RAM
CFC-Fe e PAniCo
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