| TT&C (telemetry telecontrol & communication) used in spacecraft is the most important part of the spacecraft technology. Normal space navigation relies on the TT&C system. With the development of spacecraft technology, the technology of telemetry and telecontrol has being promoted. The new and advanced technology comes forth and the old telemetry and telecontrol system is replaced or eliminated.With the spread—spectrum technology development, spread—spectrum technology is broadly used. On account of its advantage, such as low interrupt on the other channel, its hard captured for the enemy and its CDMA, and so on , it is becoming more and more important in the telemetry and telecontrol system. The spread—spectrum TT&C (telemetry telecontrol & communication) is the future spacecraft TT&C's orientation. Compared with the deficiency of tone-ranging,the spread-spectrum PN is good at space ranging. As the PN-code high performance of long period and the coherence, the very long distance and high precision ranging can be reached at the same time. Multi-target TT&C can be reached by CDMA of PN. As the advanced of PN ranging, this paper presents the PN-code's application in space TT&C.This paper presents four kinds of ranging method, including tone-ranging, PN-code ranging, carrier phase ranging and mixed ranging. The principle of ranging, source of ranging error and the comparison between them are discussed. The ranging ambiguity and the precision are studied as key points. A mixed ranging scheme is put forward, the distance and precision it can be reached are analyzed. The different performance and difficulty among these methods are analyzed. The key technology of PN-code ranging is studied, such as long periodic PN-code's design, PN-code rapid acquisition and its implement. The DLL used for the PN-code precision is simulated. The result shows that the loop filter has important influence on the tracking precision. Finally, we introduce the PN-code ranging applications in time unified system. |
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