寬頻安全通訊衛星可行性之探討

Abstract

通訊衛星的重要性不下於偵察衛星。自古以來通訊聯絡，就是關係到國家安全的重要問題。衛星通訊不受山川、河流、海洋和沙漠的地理條件的限制，具有通訊距離遠、容量大、可靠性高等優點。由於地面站對同步軌道衛星之控制、聯繫與追蹤相對來講較對其他軌道之衛星簡易許多，大部分的通訊衛星通常是在地球同步軌道運行，其軌道高度約是三萬六千公里。近十餘年來，雖也有中、低軌道的商用通訊衛星系統之建立或提議但多半不是很成功。 通訊衛星在許多先進國家都已是國家安全系統不可或缺的一環。我國幅員相對而言較為狹小，其必要性如何？可行性大不大？除了安全通訊外，有無其他的應用？其他國家發展的現況如何？等等問題都值得深入的探討。太空計畫室先前曾有Ka頻段衛星的提議，其技術難度、國外輸入可行性、我國氣候狀況之適用性又如何？也需要進一步釐清。此外，Ka頻段衛星應用於遠距教學、醫療、防災、環境保護以及緊急通訊系統等應用之可行性又如何？國內相關單位之需求又為何？都需要釐清。本論文之目的即在探討並試圖回答上述問題，以作為寬頻通訊衛星計畫系統規劃之參考。

An integrated C3I system is not only used for information collection and distribution but is also designed for prevention from being destroyed or rendered useless by enemy offensive operations. In other words, the survivability of the C3I is at least as critical as the other major capabilities of the system. At the strategic level, defense of C3I centers and the associated communications networks is crucial for maintaining an effective second-strike capability. Therefore, satellite links, because of their robustness against jamming if proper designed, has become a critical part of the C3I system for countries with advanced C3I networks. We are interested in Geostationary Ka band links for they are capable of providing extra protection margin against interference and jamming. Besides its defense applications, Ka Band satellite systems can provide the optimum solution for the distribution of broadband signals when the appropriate applications have been developed and made available at an affordable price. GPS-aided navigation is a useful application for which Ka Band is a natural candidate, especially when coupled with the provision of broadband services to mobile platforms, especially aircrafts. Other civil applications include emergency communications, flood and other natural disaster warning and environmental protection. For all its usefulness, however, Ka band satellite communication systems still have to address issues like technology feasibility concerning rain-fade compensation, on-board processing, users’ requirements, and cost/performance tradeoff. The purpose of this study is to present solutions to these related issues and investigate the feasibility of having a domestic broadband geostationary Ka-band satellite either as a component of the C3I network or as a standalone communication link and explore its civil applications.