| 摘要 |
In general, a constellation of spacecraft is used to broadcast to a particular region with high angles of view in order to reduce blockage or shadowing. A constellation of a plurality of spacecraft is placed in 24-hour orbits having inclination of about 550, eccentricity of about 0.32, semi-major axis of about 42,000 km, longitude of the ascending node of about 43° East, argument of perigee of about 270°, and longitude of the ground track at maximum latitude of about 7° East. The preferred number of spacecraft ranges from three to six. In a particular application of Digital Audio Broadcast to Europe in some embodiments, the most populous cities are provided with service from no more than about 10° from vertical, and broadcast takes place when the spacecraft are above at least 35° North latitude. The broadcast power is reduced during those portions of the orbit in which the ground track lies in the Southern hemisphere. ( 146 )
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