On-board orbit calculation and tracking system of the S band inter-satellite communication equipment (SIC) for Japan's Engineering Test Satellite-VI (ETT-VI) to be launched in 1992, is presented. The SIC provides a multibeam phased array antenna with 54 phase shifters for beam pointing. The beams are directed to any desired user satellites automatically by controlling 54 phase shifters according to results of on-board orbit calculations by an on-board microprocessor. As accurate on-board beam pointing is required in inter-satellite communications, this paper describes a method of on-board orbit calculation and estimations of beam pointing errors caused by using the system considering perturbations.
A Hall acceleration model in an applied-field MPD thruster has been constructed. This model predicts that the thruster performance is characterized by a parameter B2/m (applied magnetic field strength squared over mass flow rate). When this parameter is larger than a critical value, the Hall current is a decreasing function of B2/m and the increase in thrust becomes small. The importance of the parameter B2/m was verified by experimental studies using a 10kW steady-state MPD thruster.
A higher order theory for bending of homogeneous orthotropic elastic plates has been developed in the preceding paper. In the present paper, the theory is applied to some illustrative problems to test its accuracy and usefulness in comparison with the Reissner type theory and classical theory. Two problems are selected; (1) cylindrical bending of a simply supported rectangular plate of infinite length due to lateral pressure, and (2) bending of a simply supported rectangular plate due to sinusoidal pressure. These problems have been being used as benchmark problems because exact solutions of three-dimensional elasticity can be calculated without much difficulty. The results of the numerical calculations show that the higher order theory is much superior in the accuracy to other plate theories. As far as the stresses are concerned, an excellent agreement is observed between the higher order theory and elasticity solutions in broad range of geometric parameters.
Through the use of Venus and Earth gravity assist (VEGA) which significantly increase the spacecraft heliocentric energy it is possible to deliver a spacecraft to the outer planet and the asteroid with a low launch energy but with the additional flight time from Earth to Venus and back to Earth. A numerical investigation for this kind of VEGA trajectory returning to Earth June 1992-January 2002 indicates that similar spectra occur at the synodic interval of 583.9 days (1.6yrs) for Venus and Earth. Also, these spectra repeat in 8 year cycles of 5 opportunities.