| 摘要 |
In a system used for determining the orbital position of a spacecraft, the distance measuring signal code A, code B, code N transmitted between an earth station 100 and the spacecraft 400 is produced by modulating a set of pseudo-random pulses at a high repetition rate with binary data at a slow repetition rate; each pulse is then separated into two half-pulses and every other half-pulse is inverted. The measuring signal retransmitted by the spacecraft is picked up at an earth station where the received signal is compared with a local replica of the code and the difference signal is used to control any drifting between the local code and the received signal in order to establish synchronism between these signals. This method makes it possible to transmit a communication signal at the same time as several measuring signals on the same carrier frequency with negligible mutual interference. <IMAGE>
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