| 摘要: | 我國第一顆兼具科學與通信任務的人造衛星中華衛星一號已於1999年1月27日發射升空。根據先前的規劃，中華衛星一號將使用Ka波段的電磁波作為地面站與人造衛星之上鏈(28.25 GHz)與下鏈(18.45 GHz)的通訊聯繫之用，其中並包括19.5 GHz的標識訊號。當此種毫米波在地球大氣通道中傳播時，由於受到大氣種種因素的影響，如氧分子與水汽的吸收作用，大氣折射指數垂直與水平分布不均所造成的折射效應，大氣亂流所產生的閃爍現象，以及雨滴的吸收與散射作用所產生的訊號衰減與去極化現象等等，均使得毫米波發生異常傳播現象，而造成地面站與人造衛星之間通信品質的降低。為了要充分利用中華衛星一號所使用的Ka波段電磁波中隱含的各種可能訊息，以進一步配合中華衛星一號的科學研究與通信的任務，本計劃將利用中華衛星一號Ka波段的標識訊號，配合地面接收站的各項軟硬體設備，進行傳播通道的實驗。此項研究工作將包括台灣地區的降雨衰減特性實驗，去極化特性實驗，對流層閃爍實驗，抗衰減方法(如空間分集法)，天空噪音溫度量測實驗，低仰角人造衛星傳播實驗等等。在進行上述各項實驗以前，有關實驗所需的各項地面硬體設備性能參數的基本了解，人造衛星訊號和雨量資料的蒐集，分析與處理的方法，各項實驗方法的調查與整理，其他重要相關觀測儀器(如氣象雷達，探空儀與特高頻雷達等)的配合程度，均必須作完整的評估與規劃，以確保各項實驗的順利執行。希望經由本計劃的執行結果，能對Ka波段人造衛星訊號在台灣地區的傳播特性有進一步的了解，以作為日後利用Ka波段人造衛星訊號有關應用與研究的基礎。除此之外，在本計畫中將亦執行中華衛星一號ECP科學酬載可移動式地面接收站(TGT)之維護計畫，定期保養以及維護TGT，以維持該站之順利運作。 The ROCSAT-1 with the missions of scientific research and communication was launched on January 27, 1999. According to the system design of the specification of ROCSAT-1, the frequencies of this satellite for Experimental Communication Payload (ECP) are Ka band (28.25 GHz for uplink and 18.45 GHz for downlink) with the beacon frequency at 19.5 GHz. As this kind of millimeter waves propagate through the atmosphere, the degradation of earth-satellite communication links may take place due to atmosheric effects, such as the absorption effect of gaseous molecules O2 and H2O, scattering and diffraction effects through refractivity irregularities, severe attenuation owing to the scattering and absorption by rain particles, and abnormal refraction by stratification of atmospheric structure. In order to sufficiently utilize the information embedded in the Ka band for future application, the Ka band propagation experiments for ROCSAT-1 are proposed. The main objectives involved in this proposal are to conduct experiments for rain attenuation, depolarization, and tropospheric scintillation, and so on, using Ka band transponder of ROCSAT-1. Moreover, the techniques of overcoming rain attenuation, such as uplink power control and space diversity, will be also carried out in this proposal. Through this study, a thorough understanding of the characteristics of the Ka band propagation over Taiwan area can be achieved and the experimental results are capable of being employed for further application to the mission of Ka band satellite communication. In this proposal, the plan for the maintenance of transportable ground terminal (TGT) for ECP payload of ROCSAT-1 is also included. Through routinely maintaining and calibrating TGT, we hope that this terminal could be operated smoothly and have great benefit to the scientific missions of ECP payload. 研究期間：9201 ~ 9206 |
