久世 宏明

Average concentration of carbon dioxide (CO2) has been measured over a path length of 5.1 km in the lower troposphere by the method of differential optical absorption spectroscopy (DOAS) using a near-infrared light source based on amplified spontaneous emission. The analysis of CO2 absorption intensity around 1575 nm observed during 10 days over the Chiba city area has revealed that the CO2 concentration varied in the range of around 360-450 ppmv, with presumable influence of air mass advection from nearby industrial facilities. In addition, a good correlation has been found in relative humidity values between the DOAS and meteorological station data. As a whole, the present result indicates the usefulness of such a DOAS approach for measuring the concentration of CO2 averaged over an optical path of a few kilometers in the lower troposphere. (C) 2015 Optical Society of America

Concentration measurement of oxygen gas is required for better monitoring and control of various types of combustion systems. As compared with conventional zirconia oxygen sensors, tunable diode laser absorption spectroscopy can provide faster response, with smaller interference of inflammable gases. In this paper we report the concentration measurement of oxygen molecules using the absorption band (A-band) of 760 nm wavelength. A periodically poled LiNbO₃ crystal (PPLN) is employed for the frequency doubling of 1520 nm light from a distributed feedback laser, resulting in the 760 nm output power of 1.8 mW. The wavelength modulation spectroscopy with dual beam configuration enables the cancellation of the common mode noise from diode laser as well as excess etalon noise that arises from optical paths including the PPLN module. With the cell length of 200 mm, the absorption measurement using the R11Q12 line at 760.445 nm has led to a minimum detectable absorbance of 3.7×10^-4 m^-1. A dynamic response faster than 1 s was seen when the oxygen concentration was changed between 0% and 24% while the laser wavelength was fixed at the absorption peak.

Fluorescence originating from chlorophyll provides information on the photosynthetic activities of vegetation. We have developed a ground-based remote sensing observation system that enables the stand-off measurements of fluorescence spectrum as well as two-dimensional distribution of fluorescence imagery. The initial laboratory test was conducted by means of the laser induced fluorescence (LIF) method and solar radiation reflected from a cold mirror. Also we describe the field observation based on the direct solar radiation induced fluorescence (SRIF) scheme that has been applied to various vegetation canopies with stand-off distances of 20-30 m.

We propose a stand-off system that enables detection and classification of CBRNe (Chemical, Biological, Radioactive, Nuclear aerosol and explosive solids). The system is an integrated lidar using a high-power (terawatt) femtosecond laser. The detection and classification of various hazardous targets with stand-off distances from several hundred meters to a few kilometers are achieved by means of laser-induced breakdown spectroscopy (LIBS) and two-photon fluorescence (TPF) techniques. In this work, we report on the technical considerations on the system design of the present hybrid lidar system consisting of a nanosecond laser and a femtosecond laser. Also, we describe the current progress in our laboratory experiments that have demonstrated the stand-off detection and classification of various simulants. For the R and N detection scheme, cesium chloride aerosols have successfully been detected by LIBS using a high-power femtosecond laser. For the B detection scheme, TPF signals of organic aerosols such as riboflavin have clearly been recorded. In addition, a compact femtosecond laser has been employed for the LIBS classification of organic plastics employed as e-simulants.

Fusion of images with different spatial resolutions has the capability of improving visualization and spatial resolution and enhancing structural/textural information of the involved images, while preserving the spectral information in multi-spectral (MS) images. In this paper, various fusion methods have been examined in the data fusion of GeoEye-1 and QuickBird imagery, followed by subsequent image control. The effectiveness of five techniques, the Gram-Schmidt (GS), high-pass filtering (HPF), modified intensity-hue-saturation (M-IHS), fast Fourier transform (FFT)-enhanced IHS (FFT-E) and wavelet principal component analysis (W-PCA), has been evaluated through visual inspection, histogram analysis and correlation analysis. Also, image quality information is assessed by means of global spectral information (relative dimensionless global error, relative average spectral error), spectral distortion (peak signal-to-noise ratio), spectral (bias, root means square error) and spatial information (mean, standard deviation) of the fused images. In addition, the extraction of object boundary is tested and evaluated using Canny edge detection. The results show that most of the image fusion techniques preserve spectral information of original image, but occasionally with some spectral distortion. It has been found that the GS method, followed by HPF, yields the best information quality in the fused image, suitable for improving visual interpretation and data quality from the viewpoint of remote sensing applications.

Indonesia is undeniably true is one of the most disastrous country in the world when it comes to incidences of natural disaster. Besides its geologic setting of being squeezed by three major tectonic plates (Eurasian, Pacific and Indo-Pacific plates), its location in tropical region makes it also vulnerable in terms weather imposed disaster such as flood, landslides and typhoon. On the other hand, remote sensing technology has been developed intensively and extensively for the use of natural disaster mapping. On March 24, 2004, one of the major landslides occurred at the head of Jeneberang River in Bawakaraeng Mountain inactive volcano complex bringing huge amount of debris flowing to the lower stream of the river which endangered the Bili-Bili Dam in the district of Gowa, South Sulawesi. The Dam is very essential to the city of Makassar for the supply of drinking water and electrical power plant. This study aims to monitor the distribution and the surface displacement of the uncontrolled collapsed material of the previous landslide from the potential of material blockage to the Bili Bili Dam and possibility of future landslide by utilizing the Japanese Advanced Land Observation Satellite (ALOS) with Phased Array type L-band Synthetic Aperture Radar (PALSAR) images in the Differential Interferometric of Synthetic Aperture Radar (DInSAR) processing technique in three consecutive years of 2007, 2008 and 2009. With this technique the surface deformation of the landslide area can be measured and validated with ground measurement of Global Positioning System (GPS) and direct ground survey. Landsat images were also used to analyze the spatial extent of the area. The result shows the surface deformation occurred along the path of the collapse material where river discharge becomes an erosive agent that weakened the strength of the material cohesion which in turn creates further landslides. This phenomenon is dangerous to the people, crops and cattle surfacing this area. Therefore this area especially where cracks are found needed to be mapped and monitored and the result of the study must be distributed. In conclusion, this study is able to show that DInSAR technique with ALOS PALSAR image data can be used to monitor the post landslide area and to support the creation of landslide susceptibility map of the area. Small movement of cracks of 5-10 cms can be mapped in some parts of the surface displacement area. Using remote sensing technology this effort is effective and efficient to map such a large area.

Disasters, both natural and man-made, are increasing in their frequency and catastrophic impact in Indonesia. The Japanese L-Band SAR sensors satellite data (ALOS PALSAR) has ability to monitor disasters and measure any change occurred on earth surface. In this research, we proposed the usage of Differential Synthetic Aperture Radar Interferometry (DInSAR) to monitor landslide hazard in Kayangan catchment area, Yogyakarta, Indonesia. DInSAR is a remote sensing technique that can be used to accurately detect ground displacement or land deformation in the antenna line-of-sight (slant-range) direction using Synthetic Aperture Radar (SAR) data taken at two separate acquisition times. The DInSAR method is complementary to ground-based methods such as leveling and global positioning system (GPS) measurements, yielding information in a wide coverage area even when the area is inaccessible. The landslide map is generated over each area according to the DInSAR result. Our analysis reveals that Kayangan catchment area exhibits clear indications of slight movement in study area. The analysis result of land deformation was used to identify the acceleration caused by a destabilizing anthropogenic change and the relationship among seasonal precipitation and deformation variability. Copyright © (2013) by the Asian Association on Remote Sensing.

The application of a hyperspectral camera to the analysis of aerosol optical property is described. As compared with conventional instruments such as a skyradiometer, imaging measurement is advantageous because of its capability of obtaining spatial distribution of scattered solar radiation with exact identification of the solar disk position in an image. In particular, it has been demonstrated that the aureole information is useful for constraining aerosol properties.

Image fusion is a useful tool for integrating a high resolution panchromatic image (PI) with a low resolution multispectral image (MIs) to produce a high resolution multispectral image for better understanding of the observed earth surface. Various methods proposed for pan-sharpening satellite images are examined from the viewpoint of accuracies with which the color information and spatial context of the original image are reproduced in the fused product image. In this study, methods such as Gram-Schmidt (GS), Ehler, modified intensity-hue-saturation (M-IHS), high pass filter (HPF), and wavelet-principal component analysis (W-PCA) are compared. The quality assessment of the products using these different methods is implemented by means of noise-based metrics. In order to test the robustness of the image quality. Poisson noise, motion blur, or Gaussian blur is intentionally added to the fused image, and the signal-to-noise and related statistical parameters are evaluated and compared among the fusion methods. And to achieve the assessed accurate classification process, we proposed a support vector machine (SVM) based on radial basis function kernel. By testing five methods with WorldView2 data, it is found that the Ehler method shows a better result for spatial details and color reproduction than GS, M-IHS, HPF and W-PCA. For QuickBird data, it is found that all fusion methods reproduce both color and spatial information close to the original image. Concerning the robustness against the noise, the Ehler method shows a good performance, whereas the W-PCA approach occasionally leads to similar or slightly better results. Comparing the performance of various fusion methods, it is shown that the Ehler method yields the best accuracy, followed by the W-PCA. The producer's and user's accuracies of the Ehler method are 89.94% and 90.34%, respectively, followed by 88.14% and 88.26% of the W-PCA method. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.

Oxygen-17 is a stable oxygen isotope useful for various diagnostics in both engineering and medical applications. Enrichment of O-17, however, has been very costly due to the lack of appropriate methods that enable efficient production of O-17 on an industrial level. In this paper, we report the first O-17-selective photodissociation of ozone at a relatively high pressure, which has been achieved by irradiating a gas mixture of 10 vol% O-3-90 vol% CF4 with narrowband laser. The experiment was conducted on a pilot-plant scale. A total laser power of 1.6W was generated by external-cavity diode lasers with all the laser wavelengths fixed at the peak of an absorption line of O-16 O-16 O-17 around 1 mu m. The beams were introduced into a 25-m long photoreaction cell under the sealed-off condition with a total pressure of 20 kPa. Lower cell temperature reduced the background decomposition of ozone, and at the temperature of 158 K, an O-17 enrichment factor of 2.2 was attained. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.3702565]

Recent advances in image sensor and information technologies have enabled the development of small hyperspectral imaging systems. EBA JAPAN (Tokyo, Japan) has developed a novel grating-based, portable hyperspectral imaging camera NH-1 and NH-7 that can acquire a 2D spatial image (640 x 480 and 1280 x 1024 pixels, respectively) with a single exposure using an internal self-scanning system. The imagers cover a wavelength range of 350 - 1100 nm, with a spectral resolution of 5 nm. Because of their small weight of 750 g, the NH camera systems can easily be installed on a small UAV platform. We show the results from the analysis of data obtained by remote sensing applications including land vegetation and atmospheric monitoring from both ground-and airborne/UAV-based observations.

The technique of differential optical absorption spectroscopy (DOAS) is applied to monitor concentrations of nitrogen dioxide (NO2) and aerosol, the major pollutants in the urban atmosphere. Two DOAS paths with optical distances of a few kilometers have been set up in the Chiba city area. The spectra of visible radiation emitted from xenon flashlights installed on tall constructions are analyzed in comparison with the laboratory spectrum of NO2. The intensity stability of the light sources enables the retrieval of aerosol extinction along the paths. It is found that the temporal behavior of both pollutants is similar to those observed at nearby ground sampling stations, though the effect of difference in the observation height often appears. Wind Doppler lidar measurement has also been undertaken from an observation site near an industrial complex along the Tokyo Bay, suggesting the influence of wind direction on the pollutant concentrations observed in the region.

A novel circularly polarized microstrip antenna using triple proximity-fed method is proposed in this paper. The circular polarization radiation is produced by adjusting 120 degrees phase shift between the feeds. In the feeding network, a three-way circular-sector power divider is adopted to distribute the current equally to each feed. A method of moments is employed for optimizing the design and achieving a good circular polarization at the center frequency of 1.28 GHz. The measured result shows that 3-dB axial ratio bandwidth and maximum gain are about 0.68% (8.7 MHz)and 7.11 dBic, respectively, which are consistent with the simulated values of 0.70% (9.0 MHz) and 7.21 dBic. The narrow bandwidth and reasonable gain indicate that this antenna is promising for various applications in L-band. (C) 2011 Elsevier GmbH. All rights reserved.

Atmospheric Data Collection Lidar (ADCL) of the Center for Environmental Remote Sensing (CEReS), Chiba University, is a multi-wavelength lidar system designed for measuring tropospheric aerosols and clouds with ancillary data from ground-based aerosol measurement instruments. In this paper, we report on the concept of aerosol and cloud retrieval based on vertical, slant-path, and plan-position indicator (PPI) lidar measurements in combination with aerosol measurements conducted with a three-wavelength integrating nephelometer, an aethalometer, and a particle counter. It is expected that such a combined approach makes it possible to study the detailed features of aerosols in the troposphere, including the aerosol-cloud interaction.

We built a differential optical absorption spectroscopy system to measure near-surface CO2 absorption in the atmosphere using a nanosecond white light continuum. The white light laser can cover wavelengths ranging from 420 to 2400 nm, where the CO2 and H2O absorption lines are located. At an optical path length of 568 m, it was possible to evaluate atmospheric CO2 concentration from absorption bands of CO2 and H2O in the vicinity of 2000 nm detected by broadband white light simultaneously. (C) 2011 Optical Society of America

Spatial patterns of future atmospheric warming presented by climate model projections indicate that the temperatures of the lower troposphere will increase markedly at high latitudes in the Northern Hemisphere and also the upper troposphere at low-middle latitudes. In this study, potential impacts of the spatial patterns of future atmospheric warming on Asian dust emission were investigated by performing numerical experiments using a dynamical downscaling method. After three significant Asian dust outbreak events were reproduced as control runs, initial and boundary conditions of the control runs were updated by adding differences in atmospheric variables between the future climate (2091-2100) and the recent climate (1991-2000) to execute pseudo global warming runs. The results showed that the dust emission fluxes in the main Asian dust sources (MADSs), i.e., the Taklimakan and Gobi deserts, decrease markedly in the future climate condition. The future decreases in the dust emission fluxes are likely to be caused by a combination of the relatively large increases in sea level pressures (SLPs) in MADSs and the small SLP changes to the north of MADSs, which reduces the meridional SLP gradients between the two areas and consequently weakens cold air outbreaks. The large SLP increases in MADSs may be due to a northward shift of storm tracks and increased atmospheric stabilities caused by the large upper-tropospheric warming at low-middle latitudes. The small SLP changes to the north of MADSs corresponded to the large increases in surface air temperatures, which would be influenced by the large lower-tropospheric warming at high latitudes. (C) 2011 Elsevier Ltd. All rights reserved.

The portable automated lidar (PAL) has been shown to be effective in observing cloud dynamics and aerosol optical properties in the troposphere. The continuous monitoring of the atmosphere has indicated that the detection range is limited during daytime due to noise from the sky radiance. Here we apply the wavelet denoising method to improve the signal-to-noise ratio (SNR) of the time-dependent PAL data. As a result, SNR increased by 7.9% when compared to data smoothing based on moving average. Moreover, the analysis of wavelet coefficients enables direct retrieval of the cloud base height. It is found through manual comparison that this method shows 4.4 times less false positive and 2.2 times less false negative detection on average, when compared to a conventional method such as the threshold method. © 2011 AOS.

The spectral intensity of direct and scattered solar radiation is of fundamental importance for various studies in civil engineering, agriculture, solar power generation, and radiation budget estimation. In this paper, we describe a ground-based, wide-spectral-range sensor that can be used for measuring spectral intensities both in the visible and near-infrared spectral regions. The measurements are conducted either with artificial light sources or direct/scattered solar radiation. The measured spectra yields information on the absorption features of atmospheric gases such as nitrogen dioxide (NO2), carbon dioxide (CO2) and water vapor, as well as aerosol optical properties in the atmosphere. Relatively weak absorption of nitrogen dioxide is measured with the technique of differential optical absorption spectroscopy (DOAS), whereas aerosol, carbon dioxide, and water vapor amounts are measured by matching the observed spectra with simulated ones. Both High Resolution Transmission (HITRAN) and Moderate Resolution Atmospheric Transmission (MODTRAN) database/codes are used to derive column amounts of absorbing molecular species and to characterize aerosol optical properties.

We have developed an array antenna consisting of 12 elements of simple square-shaped, corner-truncated patches for circularly polarized synthetic aperture radar (CP-SAR) operated in the L-band. The corporate feed design concept is implemented by combining a split-T and a 3-way circular-sector-shape power divider to excite circularly polarized radiation. The fabricated antenna based on the simulation using moment method gives a good circular polarization at the center frequency of 1.27 GHz with an impedance bandwidth of 6.1% and 3-dB axial ratio bandwidth of 1.0%, satisfying the specification for our circularly polarized synthetic aperture radar intended for use onboard an unmanned aerial vehicle and a small satellite.

Pan-sharpening is also known as image fusion, resolution merge, image integration and multi sensor data fusion has been widely applied to imaging sensors. The purposes of pan-sharpening is to fuse a low spatial resolution multispectral image with a higher resolution panchromatic image to produces an image with higher spectral and spatial resolution. In this paper, we are investigated these existing pan-sharpening methods based on visual and spectral analysis. And to achieve assess the accurate classification process, we proposed a Support Vector Machine (SVM) based on Radial Basis Function (RBF) kernel. In the Experimental results, a comparative performance analysis of techniques by various methods show that Gram-Schmidt followed by RCA perform best among all the techniques. Besides that, higher overall accuracy of Gram-Smidth (GS) fused image increase 0.90 percent. And also, the high producer's and user's accuracy average of Gram-Smidth (GS) fused for each of the classes and methods used was always reported greater than 91.8% and 91.11%, respectively, indicating the overall success of the performed classification. And producer accuracy he followed by RCA was 90.84% and user accuracy was 89.99. © 2011 Academic Journals Inc.

The advancement of remote sensing technology has contributed to a significant level of assistance in reducing nature's calamities, threatening both human lives and property in its immediate vicinity. Volcanic eruption is one of a kind where the dangerous environment surrounding it also causes great difficulties for close-up monitoring and surveillance. Differential Synthetic Aperture Radar Interferometry (DInSAR) is a technique useful for accurately detecting the ground displacement or land deformation in the antenna line-of-sight (slant-range) direction using synthetic aperture radar (SAR) data taken at two separate acquisitions. As one of important targets of the DInSAR analysis, we have studied the volcanic eruption of Miyakejima island, successfully demonstrating the detection of land deformation around its crater.

We propose a new circularly polarized elliptical microstrip antenna intended for use in circularly polarized synthetic aperture radar (CP-SAR) systems operated in L-Band (1 27 GHz) The design and fabrication process aim to fulfill the challenging specification for our CP-SAR onboard unmanned aerial vehicle (UAV) We apply the proximity-coupled single feeding method by a microstrip line positioned 45 counterclockwise to the semi-major axis of the ellipse to generate the left-handed circularly polarized wave radiating from the patch Both simulated and measured results are presented For a single-element model the simulation gives an axial ratio bandwidth ( < 3 dB) of about 0 85% (10 8 MHz) which is consistent with the bandwidth measured for the measured fabricated model of 082% (10 4 MHz) and 091% (11 6 MHz) simulated for an antenna array model These results satisfy the specification for our CP-SAR sensor onboard UAV (C) 2010 Elsevier GmbH All rights reserved

Various methods proposed for image fusion satellite images are examined from the viewpoint of accuracies with which the color information and spatial context of the original image are reproduced in the fused product image. Image fusion is a useful tool in integrating a high resolution panchromatic image (PI) with a low resolution multispectral image (MIs) to produce a high resolution multispectral image and better understanding of the observed earth surface. In this study, five typical fusion methods of Gram-Schmidt (GS), Ehler, modified intensity-hue-saturation, high pass filter, and wavelet-principal component analysis (PCA) are compared. The spectral quality assessment of the products using these different methods is implemented by image quality metrics. The accuracy of classification result is assessed by means of the support vector machine based on radial basis function kernel. Our analysis indicates that as a whole, the Ehler and wavelet-PCA method show good performances, followed by GS. Also, the examination of confusion matrix shows that both Ehler and wavelet-PCA yield better accuracies in the classification results.

The L-band of LHCP and RHCP array antenna for circularly polarized synthetic aperture radar (CP-SAR) has been developed using simple corner-truncated square-patch elements. The corporate feed design concept is implemented by combining a split-T and a 3-way circular-sector-shape power divider to excite circularly polarized radiation. The fabrication of both antennas based on the simulation using the method of moment (MoM) gives a good circular polarization. Impedance bandwidth and 3-dB axial ratio bandwidth for LHCP are 6.1% and 1.0%, respectively, while for RHCP are 6.2% and 1.0%, respectively. The full antenna (four panels), will be installed on an Unmanned Aerial Vehicle (UAV) JX-1 in Center for Environmental Remote Sensing, Chiba University. In the future, CP-SAR is expected to improve the characteristics of conventional SAR system, especially to extract some new physical information on the earth surface.

Differential optical absorption spectroscopy (DOAS) is useful for various types of trace gas measurements in the lower troposphere. In this paper, we report the DOAS measurement conducted in Chiba, Japan during 2009 and 2010. An optical path length of 5.5 km is employed to measure the average concentration of NO(2) using a xenon aviation obstruction light that flashes every 1.5 s. By virtue of the high stability of the light source intensity, the intensity measurement enables the retrieval of aerosol extinction coefficient averaged over the optical path. The results are compared with the concurrent results of ground sampling and sunphotometer measurements. (C) 2010 Elsevier Ltd. All rights reserved.

Long-term characterization of tropospheric aerosol has been carried out at Chiba, Japan, using a compact, stand-alone spectroradiometer under clear-sky conditions between August 2007 and March 2009. The spectra of direct solar radiation, aureole, and scattered solar radiation in various directions are observed in a wavelength range between 350 and 1050 nm with an optical resolution of 10 nm. Radiative transfer calculation using the MODTRAN4 code is employed to retrieve aerosol optical parameters such as aerosol optical depth (AOD), extinction coefficient, single-scattering albedo, scattering phase function, and asymmetry parameter, as well as water vapor column amount. The retrieved value of AOD varies in the range 0.1-0.5, while the water vapor column amount changes from 0.2 to 4 g/cm(2), showing reasonable agreements with the concurrent measurements with a sunphotometer and a microwave radiometer, respectively. The seasonal variation of the retrieved parameters indicates the major impacts of dust particles in spring, sea salt particles in summer, and anthropogenic fine particles in winter. (C) 2010 Elsevier Ltd. All rights reserved.

We developed a method for characterizing atmospheric properties from ground-based, spectral measurements of direct and scattered solar radiation under clear sky conditions. A compact spectroradiometer is employed for radiation measurement in the wavelength range between 350 and 1050nm with a resolution of 10nm. Spectral matching of measured and simulated spectra yields a set of optical parameters that describe optical characteristics of tropospheric aerosols. We utilize the radiative transfer code MODTRAN4 for constructing realistic atmospheric models. Details of the system calibration, analysis procedure, and the results of its performance test are described. (C) 2010 Optical Society of America

Up till now, only linearly polarized microwave radiation are employed by the Synthetic Aperture Radar (SAR) systems onboard spaceborne platforms. In general, such linearly polarized SAR (LP-SAR) systems are very sensitive to Faraday rotation in the ionosphere and platform posture, both of which will contribute to system noise superposed on the resulting backscattering signature. So as to improve the situation, currently a novel Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor is developed in our Microwave Remote Sensing Laboratory, Chiba University. As an early stage of the development of this CP-SAR sensor, we will make use of an Unmanned Aerial Vehicle (UAV) platform, called as Josaphat Laboratory Experimental UAV (JX-1) for testing CPSAR capabilities. In this paper, we describe the CP-SAR hardware system design and CP-SAR parameters calculation with its results. The possibility of implementing a smaller antenna using the new CP-SAR technique than with conventional LP-SAR systems is shown. This research will contribute to the realization of a compact CP-SAR sensor, which can be installed on a small and low cost platform yielding a high accuracy SAR image data. The experience and knowledge of CP-SAR UAV experimental will be very valuable to realize a CP-SAR sensor onboard a small satellite platform as the final stage of the CP-SAR sensor development roadmap.

We have investigated elliptical annular ring microstrip antennas having a sine wave periphery both theoretically and experimentally. The proposed antenna gives a good circular polarization at the center frequency of 1.285GHz, with measured 3dB axial ratio bandwidth of about 0.73% (9.5MHz) and impedance bandwidth of about 1.7% (22.0MHz). Input and radiation characteristics are also examined for different sine wave amplitudes applied to the periphery of elliptical ring patch antenna.

For decades, linearly polarized synthetic aperture radar (LP-SAR) systems have been used in spaceborne platforms. In the transmitting and receiving processes, Faraday rotation in the ionosphere often affects the LP signals, leading to degradation in the backscatter signature in SAR images as well as loss of available power. Although the use of circular polarization can provide a solution to the Faraday rotation problem in many microwave systems, it has not previously been applied to SAR systems. In this paper, we describe the novel concept of a spaceborne (especially small-satellite) SAR system based on circular polarization, and show that a smaller antenna size, lower transmitted peak power and high precision signal reconstruction can be achieved by the proposed circularly polarized (CP)-SAR system. © 2010 Taylor &amp Francis.