This paper describes the performance of fan rib type highly accurate, highly reproducible mesh deployable reflector with precision screw type adjustment element for surface drawing and motor and link type deployment system. Surface error and its reproducibility for repeated deployment decreased less than 1/2 of previously developed fan rib type mesh reflector with spring type deployment system. No periodic distortion which corresponds to rib arrangements can be seen and thus mesh reflector with very low gore lobe and side lobe characteristics, which is very useful for frequency reuse, is achieved in C band. This paper also presents measured higher order passive intermodulation (PIM) products of mesh developed and used for this deployable reflector with the mesh tension as a parameter.
An Kalman filter has been widely used in target tracking. In most circumstances, the exact values of model parameters, however, are unknown and adaptive filtering is necessary. In this paper, a novel target tracking approach based on adaptive Kalman filter is proposed, in which unknown process noise variance is estimated by using the measured data of an actual state. The suggested approach has certain merits over various existing adaptive algorithms and it is simple, efficient and suitable for real-time applications. As an example, the tracking of a tethered subsatellite is analyzed, and the performance of this approach is evaluated by a simulation study on a realistic system.
The effects of DC applied magnetic fields and the configuration of the discharge-channel on the performance of teflon PPTs which input energy is 15J, 30J and 125J, respectively, were studied. The results of the experiments showed that, when the accelerating magnetic field was applied, high specific impulse (-4000s) and high thrust efficiency (-34%) can be achieved and also, both impulse bit and mass shot were decreased. When the electrode length was elongated than the propellant channel length, impulse bit and mass shot were decreased and specific impulse and thrust efficiency were increased. The results of the measurements of propellant vaporization distribution along streamwise direction suggested that the cause of improvement of specific impulse and thrust efficiency by the elongation of electrode is the suppression of excessive propellant sublimation at the propellant-channel end.
Experimental studies on the physical process inside of Teflon PPT were carried out. The current distribution measurement using Rogowski coils indicated the propagation of discharge region. It was showed that elongation of the electrodes and the applied accelerating magnetic field are effective in removing discharge current from Teflon sublimation surface to reduce the amount of Teflon comsumption. The improvement in specific impulse and in thrust efficiency, which is reported in Part I, is explained by this effect. The exhaust plasma properties were measured using double probes. The measurement showed that plasma generation is deeply affected by the discharge current.
NAVSTAR/GPS is now drawing the attention of the whole world as a global infrastructure for navigation, traffic control and search and rescue of almost mobile vehicles around the world. However, there are some problems in the application of GPS at stand alone. First, GPS navigation accuracy will be intentionally degraded to protect from military abuse by the countries in disputes. Second, in the land mobile application of GPS, the view field of satellites is restricted by buildings, trees or mountains, so navigation data are lost or turn inaccurate frequently. In this paper, several methods to solve the above mentioned problems are investigated and the navigation performance of these methods is verified by carrying out the computer simulation study. The use of high precision quartz as GPS reciever's clocks, vehicle velocity data derived from delta ranges, distance data derived from vehicle speed and direction, or additional range data obtained from satellites other than GPS are considered as the effective ways to improve the accuracy and reliability of satellite navigation.