Y. Matsuzaka

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

Plastic balloons with thin polyethylene films for high altitude observations

Abstract Balloons made of thin films have been frequently used to observe high altitude winds. Such a balloon is also useful to perform some scientific observations now performed by sounding rockets. Since this balloon is lighter than a normal balloon, it can easily reach an altitude more than 40km with a payload less than 10 kg. A ceiling altitude of 48.7 km was achieved by the new balloon with a volume of 30,000m 3 in a test flight in 1995. We need to reduce mechanical stress by attaching an exhaust duct especially for a thin polyethylene balloon. Three types of exhaust ducts were tested in flights in 1995. We have confirmed good performance of the thin polyethylene balloon. The launching device for the high altitude balloon 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.

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.

‘‘Glow‐discharge’’ ionic anemometer

We have developed an ionic anemometer utilizing a glow discharge for the purpose of observing stratospheric turbulence. The anemometer has a three‐electrode structure; two electrodes made of Ni mesh hold a glow discharge between them and act as the source of ion tracers. The third electrode collects the ions interacting with wind. The minimum detectable wind speed is less than 1 cm/s over a pressure range of 15–35 Torr. The lifetime of this device is more than 50 h. The anemometer has been successfully operated on balloon‐borne experiments carried out in 1983 and 1984.

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.

Measurement of scattering coefficient σ° of trees

Abstract This paper describes (1) an indoor measurement method to sludy backscattering characteristics of trees and (2) the result of the measurements made on two kinds of conifers, Sugi (Japanese cedar) and Sawara (Japanese cypress), at C- and X-bands for polarization combinations of HH, VV, HV and VH. The discussions on the backscattering and penetration characteristics of the trees using the measured ground truth data indicate the usefulness of this method to study microwave signatures of trees.

Semi-dynamic launching method for scientific balloons

Abstract The Sanriku Balloon Center (SBC), which belongs to the Institute of Space and Astronautical Science, was built in 1971. The launching field of SBC was 140 m in length and 20 m in width. In Japan, the balloon launching method that we have been using since 1971 is a kind of static launching method. In 1998, we extended the launching field 20 m in length and created a new launcher at this point. We have recently developed a “semi-dynamic” launching method. This newly developed launcher is different from the launcher used in the dynamic launching method, it is fixed to the ground creating freedom of rotation around the vertical axis. It is also possible for the launcher to lift up a payload to a height of 5 m from the ground. We succeeded in launching the first test balloon by using this new launching method on September 6, 1999. Utilizing the new launching machine, it became possible to launch a balloon with a volume of 1,000,000 m 3 and a total lift of 2 tons, even in Japan.

Low Altitude Space Communication System

Abstract We describe a new Low Altitude Space Communication System (LASCOS), which was completed in 1996 by the Institute of Space and Astronautical Science in Japan. This system consists of a mobile balloon tracking and receiving station and networks which connect them to the Sanriku Balloon Center in Iwate Municipality and the Institute of Space and Astronautical Science (ISAS) in Kanagawa Municipality. This station and the SBC receiving station are connected via telephone lines, i. e. an Integrated Services Digital Network (ISDN) or an analog communication network. Balloon trajectory monitoring, telecommand transmission operation and telemetry data acquisition can be done from any computer terminal through the LASCOS. LASCOS has built-in flexibility to adapt to a foreign balloon station. The number of individuals necessary to operate it minimum. LASCOS will be used for long range tracking and balloon expedition. We present the results of its first test with an actual balloon flight.