H. You, Y.-W. Jan, and J.-R. Tsai (Taiwan)
Optimization, GPS, Argo.
The navigation of Argo satellite utilizes global posi tioning system (GPS). The Argo satellite flies with SUn Pointing (SUP) in the daytime, and Geocentric Attitude Pointing (GAP) in eclipse, and there will be attitude changes while exiting eclipse and start ing to photograph. Because of this periodic changing of spacecraft attitude, the GPS visibility analysis is therefore conducted to seek the optimal antenna orien tation so as to have the longest time observing at least 4 GPS satellites during flight. The criterion of visibil ity is based on the link budget which considers power loss as well as antenna and satellite orientation, and visibility refers to the condition when the carrier-to noise-density-ratio value at the receiver is greater than the minimum threshold 35 dB-Hz. Considering mixing SUP and GAP modes for the Argo satellite attitude orientation, the antenna normal will have the best vis ibility of at least 4 GPS satellites at most time if it aligns with the -Z direction in the body-fixed frame. This analysis provides a systematic way to seek the optimal GPS antenna orientation for complex satellite attitude maneuvers.
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