Haruto Hirosawa

A wavelet-based texture feature set applied to classification of multifrequency polarimetric SAR images

Texture is an essential key to the classification of land cover in SAR images. A wavelet-based texture feature set is derived. It consists of the energy of subimages obtained by the overcomplete wavelet decomposition of local areas in SAR images, where the downsampling between wavelet levels is omitted. The feature set has been successfully applied to multifrequency polarimetric images of the Flevoland site, an agricultural area in The Netherlands. The methods of polarization selection and feature reduction are also discussed.

Cross-polarized radar backscatter from moist soil

Abstract Measurements of radar backscatter from bare soil at 9.0 GHz using a broad beam, with an effective beamwidth of product patterns and an incident angle of about 17° and 30°, respectively, have shown that the sensitivity of the cross-polarized ( HV ) return to soil moisture content was much higher than that of the like-polarized ( HH ) one. Analysis of the data shows that the observed HV back scattering power has a dependency of nearly Γ 2 , where Γ is the power reflection coefficient at a plane soil-air interface. This fact suggests that multiple scattering on rough soil surface caused the soil moisture sensitivity of the cross-polarized return to be high.

Smoothing effect of wavelet-based speckle filtering: the Haar basis case

The smoothing effect of the wavelet-based speckle filtering that the authors proposed is investigated. The filtering reduces the amplitude of wavelet coefficients, and a theoretical investigation with the Haar basis derives a functional relation between the ENL and two parameters: the wavelet level and the degree of the amplitude reduction.

Measurement of microwave backscatter from a cypress with and without leaves

The relative contributions of leaves and branches to backscatter are discussed, based on the changes of the scattering coefficients. A measurement in circular polarization of the backscatter at C band is also described

High altitude balloons with ultra thin polyethylene films

Abstract The balloon group at the Institute of Space and Astronautical Science (ISAS) has studied to develop high altitude balloons that could reach an altitude of more than 40 km with a light payload in order to meet the requirements of observations at extremely high altitudes. In 1999, we developed a ultra thin balloon film with a thickness of 3.4 μm. It is synthesized with a new catalyst, metallocene, and has a ultimate strength of ∼650 kg/cm 2 at −80°C. Using the film, we made the first balloon with 1,000 m 3 in volume and 2.6 kg in weight. We launched the balloon from Sanriku Balloon Center on September 1, 1999 and it successfully reached an altitude of 37.1 km. In 2000, we prepared the second balloon with 5,000 m 3 in volume with 6.8 kg in weight. It was launched on June 7, 2000 and it successfully reached an altitude of 43.0 km. Such light weight balloons are planned to be used for scientific studies in near future.

Space Vlbi Satellite Halca and its Engineering Accomplishments

Abstract The Institute of Space and Astronautical Science (ISAS), Japan, launched a satellite named HALCA in February 1997 by the ISASs new rocket M-V. It has become the first space Very Long Baseline Interferometry (VLBI) satellite of the world by accomplishing a series of engineering experiments, representative ones of which are deployment of 8 m diameter parabolic antenna, precise attitude control of spacecraft, transfer of phase reference signal, high data-rate telemetry, single dish telescope operation, and interferometry with ground radio telescopes. Following the successful engineering experiments, HALCA has been operated for science observations under the science program named “VSOP” (VLBI Space Observatory Programme) in cooperation with many organizations and radio telescopes around the world.

Measurement of backscatter from conifers in the C and X bands

Abstract This paper describes the microwave backscattering characteristics of three kinds of conifers, Matsu ( Japanese pine), Sugi (Japanese cedar) and Sawara (Japanese cypress), in the C and X bands for polarization combinations HH, VV, HV and VH. The measurements were made indoors using rotating-tree targets. ( i) Differences between HH and VV, (ii)the levels of the like backscatters of three conifers, and ( in) depolarization are discussed in relation to the features of canopy structure and leaf shapes. The method employed in this study will be ofuse in radar-signature studies of a wide variety of trees.

Systems for long duration flights

Abstract This paper describes the systems for long duration flights developed in Japan for scientific observations. Much efforts have been expended to evolve systems for long duration flights in Japan, by controlling the balloon trajectories with a knowledge of wind pattern at high altitudes over Japan. These systems called “Cycling Balloon”, “Boomerang Balloon” and “New Boomerang Balloon” have been successfully used for the observations by keeping the balloons close to the balloon station. “Relay Balloon” is another system to extend the telemetry range by using an additional balloon as a relay station to link the telemetry from the main balloon. Some detailes of the exhaust valve, ascent meter and automatic level control devices used for the balloon control are also described in the paper.

Thin-film balloon for high altitude observation

Abstract The development of high altitude balloons will enrich many areas of scientific observation. A high altitude balloon fabricated using improved technology with thin Winzen polyethylene films has been flown in the upper atmosphere. A light weight balloon carrying small instruments can reach an altitude higher than 40 km. In contrast to sounding rockets, the balloon-borne experiment provides a unique opportunity to stay at a high altitude for more than a few hours at low cost. We have developed methods for fabricating large balloons for scientific observation and have also established a new belt sealer and successful launching system. In January 27, 1997, a thin-film balloon with a volume of 120,000 m 3 , carrying a payload of 11.8 kg, reached an altitude of 50.2 km which is the highest balloon altitude ever in Japan. This shows that a thin-film balloon is suitable for high altitude observations and can fill the gap between satellite and conventional balloon altitudes.

A new static-launch method for plastic balloons

Abstract A new static-launch method that we have developed as an improvement of our former method is described. The key procedure is to extend a whole balloon vertically upon the launcher before release, with squeezing the top bubble of the balloon by a soft collar. The new method improved the capability for heavier payload significantly. In 1981, 15 balloons, ranging from 5,000 m 3 to 50,000 m 3 in volume with a total lift from 150 kg to 650 kg, were launched by this new method successfully.