欧洲,日本間の精密時計比較用レーザー衛星の最適軌道案

A project of a series of experiments for the very precise clock synchronization by use of the laser techniques and the earth satellites has been set up recently in France. being supported by the international cooperation given by many laboratories interested in this problem. In the first phase of the project, a geostationary satellite is planned to be used. In case of the geostationary satellite as used for the clock synchronization between Europe and Japan, the elevation angle of the satellite situated at the point of equi-angular distance from Europe and Japan becomes less than 10 degrees as seen from the ground stations. This amount of the elevation angle is too low to secure the transmission of laser pulses between the satellite and the ground stations. It is proved that the elevation angle sufficient for the possible transmission can be obtained only by the satellites having the orbits which reach rather high latitude zone in the northern hemisphere. It is desirable, in this case, that the angular velocity of the satellite becomes as low as possible near the northern extreme of the orbit, where a series of laser pulses. must be shot in the experiment. <BR> In the present paper, various combinations of the inclination angle (I) and the eccentricity (e) adequate for the present purpose are examined by the numerical com-putation with respect to the synchronization satellites (n=ω, and n=2ω, n being the mean. angular velocity of the satellite and w the earth's angular velocity) which have the perigee at the southern extreme. According to the result of computations, a series of L-40°, e=0.1; I-50°, e=0.2: and I-60°, e-0.4 etc. is considered most appropriate with respect to the synchronization satellites for n=w. While, the optimum conditions are also obtained for the synchronization satellite for n=2w, however, the adequate values of e become as large as 0.5 to 0.7 which may introduce the orbital instability affected by the serious perturbations.