Josaphat Tetuko Sri Sumantyo

Dual-band circularly polarized equilateral triangular-patch array antenna for mobile satellite communications

The Japan Aerospace Exploration Agency will launch the Engineering Test Satellite VIII (ETS-VIII) in 2006 to support the next generation of mobile satellite communications covering the area of Japan (beam coverage El=38/spl deg/ to 58/spl deg/). In this paper, a satellite-tracking left-handed circularly polarized triangular-patch array antenna is developed for ground applications. The targeted minimum gain of the antenna is set to 5 dBic at the central elevation angle (El=48/spl deg/), in the Tokyo area, for applications using data transfer of around a hundred kbps. The antenna is composed of three equilateral triangular patches for both reception and transmission units operating at 2.50 and 2.65 GHz frequency bands, respectively. The antenna was simulated by method of moments (MoM) analysis, and measurement of the fabricated antenna was performed to confirm the simulation results. The measurement results show that the frequency characteristics and the 5-dBic gain coverage in the conical-cut plane of the fabricated antenna satisfy the specifications for ETS-VIII. A prototype of the proposed antenna system is employed in outdoor experiments using a pseudosatellite and shows good performance from El=38/spl deg/ to 58/spl deg/.

Assessment of pan-sharpening methods applied to image fusion of remotely sensed multi-band data

Abstract 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 producers and users accuracies of the Ehler method are 89.94% and 90.34%, respectively, followed by 88.14% and 88.26% of the W-PCA method.

Development of Circularly Polarized Array Antenna for Synthetic Aperture Radar Sensor Installed on UAV

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 1.27GHz with an impedance bandwidth of 6.1% and 3-dB axial ratio bandwidth of 1.0%, satisfying the speciflcation for our circularly polarized synthetic aperture radar intended for use onboard an unmanned aerial vehicle and a small satellite.

ALOS PALSAR D-InSAR for land subsidence mapping in Jakarta, Indonesia.

Differential synthetic aperture radar interferometry (D-InSAR) is a technique capable of detecting land surface deformation. In this research, we use Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) data to investigate land subsidence in Jakarta during 2007 and 2008. It is found that four northern areas in the city exhibit clear indications of land subsidence. The location of the centre of subsidence is estimated, and the subsidence volume is evaluated for each area using the unwrapping method as a further process of using D-InSAR results. The subsidence depth and volume around the centre are estimated to be 10–22 cm and 0.2 × 105 – 4.2 × 105 m3, respectively, in the study time period. Comparison with ground survey data indicates that the D-InSAR analysis gives reliable estimates of the subsidence in an urban environment.

Employing a Method on SAR and Optical Images for Forest Biomass Estimation

In this paper, we develop a novel method for forest biomass estimation. The intensity values of Advanced Land Observation Satellite-Advanced Visible and Near Infrared Radiometer type 2 and PRISM images and the texture features of the Japanese Earth Resources Satellite 1 image are used in a multilayer perceptron neural network (MLPNN) that relates them to the forest variable measurements on the ground. A proposed speckle noise model is also applied for modeling and reducing the speckle noise in the synthetic aperture radar (SAR) image. Reducing the speckle would improve the discrimination among different land use types and would make the textual classifiers more efficient in SAR images. Ideally, filters will reduce the speckle without loss of information. In the process of the forest biomass estimation, the filters should preserve the backscattering coefficient values and edges between different areas. We investigate both quantitative and qualitative criteria in speckle reduction and texture preservation to evaluate the performance of the proposed filter in the forest biomass estimation. We will also show that the biomass estimation accuracy is significantly improved in an MLPNN when the radar and the optical data are used in combination compared to estimating the biomass by using a single datum only. The root-mean-square error (rmse) value is decreased when the proposed method is used (rmse = 2.175 ton) compared with that of the classic method (rmse = 5.34 ton).

Long-Term Consecutive DInSAR for Volume Change Estimation of Land Deformation

In this paper, the long-term consecutive differential interferometric synthetic aperture radar (SAR) technique is used to measure the volume change during land deformation. This technique was used to investigate the subsidence of Bandung city, Indonesia, by assessing the data from two Japanese L-band spaceborne SARs (Japanese Earth Resources Satellite 1 SAR and Advanced Land Observation Satellite Phased Array type L-band Synthetic Aperture Radar) during the periods of 1993-1997 and 2007-2010. The results are confirmed using GPS observation data, ground survey data, local statistics, ground water level trend data, and the geological formation of the study area. The obtained results reveal a close correlation between the subsidence measurements and changes in the ground water level due to water pumping, population growth, industry growth, and urbanization of the study area.

Microwave and optical image fusion for surface and sub-surface feature mapping in Eastern Sahara

Synthetic Aperture Radar (SAR) is capable of penetrating a certain depth of dry sand and facilitates a unique opportunity for sub-surface imaging while optical sensors record information on sand features in the arid and semi-arid environments. Merging of radar and optical data generates greater quality images that can interpret and map the details of structural attributes in these landscapes. The current study compared different merging options to examine the effects of data fusion on object recognition. The study area is located on a sand-buried area of Eastern Sahara. Image fusion using Principal Component (PC) and intensity hue saturation (IHS) provides better results over the arithmetic (i.e. Synthetic Variable Ratio (SVR) and Brovey) and wavelet-based methods. The study also discussed the utility of data fusion for surface and sub-surface feature imaging and mapping in the desert environments.

A model for removal of speckle noise in SAR images (ALOS PALSAR)

Speckle noise is primarily due to the phase fluctuations of the electromagnetic return signals. Since inherent spatial-correlation characteristics of speckle in synthetic aperture radar (SAR) images are not exploited in existing multiplicative models for speckle noise, a speckle noise model is proposed here that provides a new framework for modelling and reducing the speckle noise. Both quantitative and qualitative criteria, including speckle reduction and texture preservation, are used to evaluate the performance of the proposed filter; one PALSAR (new Japanese sensor) image and a JERS-1 image are employed in the evaluation. The results showed that the proposed filter is slightly better than commonly used filters such as the Kuan, gamma, enhanced Lee, and enhanced Frost filters. The proposed filter can be used in different applications, including mapping and forestry biomass estimation. Furthermore, one of the benefits of the proposed filter is that it is independent of the threshold, which is required in most commonly used filters. The proposed filter was tested with SAR images of different sites in the northern forests of Iran.

Spectral information analysis of image fusion data for remote sensing applications

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.

Identifying Surface Materials on an Active Volcano by Deriving Dielectric Permittivity From Polarimetric SAR Data

Dielectric permittivity εr measured on the Earths surface is an effective property for characterizing surface materials in terms of rock type and water content, particularly in highly changeable environments such as active volcanoes. We propose a technique termed dielectric permittivity from polarimetric synthetic aperture radar (dPSAR) to quantify εr using a single scene of polarimetric SAR data, based on the small perturbation model of backscattering (SPMB). For an optimal solution, the Nelder-Mead simplex method was combined with SPMB. The application of dPSAR to a scene of ALOS PALSAR data from the vicinity of Mt. Merapi, Indonesia, correctly identified the relative value ranges of εr for pyroclastic flow and tephra deposits accompanying large eruptions that occurred on November 5, 2010; their means were 2.55 and 3.07, respectively. Pore water within porous ashes is a plausible factor for increases in the εr of the tephra.