Near-synchronous uncontrolled objects were searched using an optical telescope. The observation was planned systematically. The geostationary orbit was scanned in two nights so as to follow a definite right ascension. Seven drifting objects were detected. These orbits were estimated since a fixed point was observed in the equatorial celestial coordinates. Therefore, follow-up observation is easy even if these are not tracked constantly. As a result, the proper orbits of four objects were determined. The observation procedure is appropriate for parallel measurement of near-synchronous debris.

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A new ballon design method named ‘three-dimensional gore design’ was developed. It is based on a pumpkin shape balloon with bulges of small radii between adjacent load tapes without the help of film extensibility. This type of balloon can be manufactured with gores having a size larger than that of the conventional gore. The sides of each gore are fixed to the adjacent short load tapes with controlled shortening rates. The gore length is chosen so as not to create any meridional tension. Hence, the superpressure limit of these balloons is simply given as film strength divided by bulge radius. As the limit does not depend on the balloon size, a large balloon with a high superpressure limit can be easily constructed without strong films. A test flight as well as indoor inflation and burst experiment showed that this new design method can realize a larger and lighter superpressure balloon capable of suspending a heavy payload in the stratosphere.

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An effective method to keep cushion pressure constant under fluctuation of cushion volume of SES is proposed and examined experimentally. In general, the fluctuation is induced by wave pumping. In the method an air jet with the length equal to the width of the air cushion is adapted. The air cushion is formed by this jet and sealed at one side. On the other hand, the opposite side is sealed with a material like as a skirt. The air nozzle that supplies the air jet can revolve to control the cushion pressure. In experiments a two-dimensional air cushion model of SES was used, where the wave pumping was simulated by a piston. Angle of the air nozzle was changed dynamically to eliminate the fluctuation of cushion pressure occurred by the piston. The experimental results show that the fluctuation of the cushion pressure became drastically extinct. The availability of this method was cleared and proved.

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The purpose of this study is to analyze human pilot behavior at landing operation. The pilot model is constructed using neural network from the results of the simulator tests. The inputs to this model are observation cues such as the horizon and the runway, and pilot control inputs. The output is the elevator angle. The data on two cases (with wind, or with no wind) are used for learning. The constructed pilot models are simulated in various cases and their validity and generalization are investigated. Finally, the importance of each input is evaluated using factor analysis of the Neural Network model.

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Institute of Space and Astronautical Science has developed a cathodeless microwave discharge neutralizer for the microwave ion engine system. In order to clarify the electron emission mechanism of the microwave neutralizer, electron current characteristics as well as plasma parameters inside the neuralizer were measured. The electron current was greatly influenced by the material of the neutralizer orifice. Among several materials with different work functions, an orifice made of tungsten impregnated with barium-oxygen showed the best performance. It is concluded that by adopting a low-work-function material, the secondary-electron emission by the singly-charged-ion impact was emphasized, and thereby the electron current was increased.

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