摘要
Chang＇E-3 spacecraft was orbiting the Moon from December 6 14, 2013, and very long baseline interferometry （VLBI） observations were performed to improve the accuracy of its orbit determination. In the process of recording VLBI raw data, 2 bits quantization was implemented. Interesting phenomenon was that signal-to-noise ratio （SNR） of each VLBI station experienced periodical change and had large variation on amplitude while in the Moon＇s orbit, whereas SNR kept in a stable level after Chang＇E-3 landed on the Moon. Influence of varying elevation angle on SNR was analyzed and compensation of 2 bits quantization harmonics to SNR calculation was investigated. Most importantly, telescope system noise temperature increase caused by the Moon was computed along the time of Chang＇E-3 orbiting the Moon, and well matched SNR changing trend in terms of correlation coefficients.
Chang＇E-3 spacecraft was orbiting the Moon from December 6 14, 2013, and very long baseline interferometry （VLBI） observations were performed to improve the accuracy of its orbit determination. In the process of recording VLBI raw data, 2 bits quantization was implemented. Interesting phenomenon was that signal-to-noise ratio （SNR） of each VLBI station experienced periodical change and had large variation on amplitude while in the Moon＇s orbit, whereas SNR kept in a stable level after Chang＇E-3 landed on the Moon. Influence of varying elevation angle on SNR was analyzed and compensation of 2 bits quantization harmonics to SNR calculation was investigated. Most importantly, telescope system noise temperature increase caused by the Moon was computed along the time of Chang＇E-3 orbiting the Moon, and well matched SNR changing trend in terms of correlation coefficients.
基金
supported by the National Natural Science Foundation of China(Nos.11473059,11273049,11403082)
