| Summary: | 博士 === 國立中央大學 === 機械工程研究所 === 92 === The main goal of this dissertation focuses on the low-cost space mission and constellation design for acquiring weather images of Taiwan. Due to the low-cost requirement, the passive magnetic attitude control system is employed. The components of bus-system also use as many of off-the-self parts as possible. The primary payload of spacecraft is the imagery system possessed the CCD camera with wide angle of field of view.
This dissertation contains two main subjects: the imagery system design and the constellation design. In Chapter 2, the mission requirements, imaging requirements, pointing requirements and coverage requirements are defined and analyzed according to the mission objectives. In Chapter 3, the imagery system is designed according to the mission requirements defined in Chapter 2. According to the characteristics of attitudinal and orbital motion of spacecraft, the shooting zone and imaging logic are designed for acquiring weather images of Taiwan per day. The maximal and mean reference pointing errors are defined to analyze the pointing error of imagery system. The calculation result shows that the minimum pointing error can be obtained by means of employing an optimal setup angle of CCD cameras. It is found that the imagery system design for Taiwan can be applied to the other targets located at the same geomagnetic latitude as that of Taiwan. Furthermore, the imagery system with multi-cameras is extended to observe an area target at a specified geomagnetic latitude band.
In Chapter 4, a constellation for acquiring the weather images of Taiwan hourly is designed according to the coverage requirements defined in Chapter 2. The bus-system and imagery system designed in Chapter 3 are also employed in the satellites of constellation. The calculation result shows that the 14/14/0 Walker constellation can satisfactory meet the mission requirement of taking pictures hourly. The analysis of present constellation design also shows that the maximal coverage gap of 14/14/0 constellation is less than one hour at the latitude band of ± 33 deg N. The combination of 14/14/0 constellation and the imagery system of multi-cameras in Chapter 3 can provide the weather images of an area target, which is located at a specified geomagnetic band. This result is also applied to observe a moving target, such a typhoon, within a warning area including Taiwan. The simulation of observing typhoon Taraji shows that 127 images can be acquired during 102 hours.
In Chapter 5, the conclusions of this dissertation are given and the suggestions of the future applications of present study are also proposed.
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