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In radio astronomy observations, radio frequency interference (RFI) is mixed into the telescope receiving system in various forms. The existence of RFI brings misjudgment to the observation or reduces the observational signal-to-noise ratio. In recent years, the domestic and overseas radio astronomy has developed rapidly. Large-scale radio telescopes and telescope arrays at home and abroad have been constructed successively. Observation sensitivity is greatly improved, and the influence of RFI is particularly prominent. With the development of science and technology and the intensification of human activities, the RFI has become increasingly serious and irreversible. We propose to use the two-dimensional discrete wavelet transform method to analyze the data of radio astronomy observations, and to perform wavelet transform on the time-frequency sequence output by the telescope system. According to the wavelet coefficients, the every component in the original signal is separated, and the corresponding threshold value is obtained by the statistics on each component. Each component is compared with the threshold to identify the interference component, and to mark it for removal. This method is used to process the actual observation data. The results show that this method can well mark and eliminate the interference signal, and improve the observational signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

In order to carry out the spectral observation with the TM65m radio telescope, the frequency calibration and test of DIBAS (Digital Backend System) are performed, it is found that it has a good performance. First, by injecting the PCAL signals, the frequency resolution, frequency drift and the stability of frequency interval between two spectral lines of the DIBAS backend are measured. It is found that in one hour, the maximum frequency drift of a single spike is 0.03 channel, the maximum fluctuation of spike interval is 0.05 channel. Then, by the observations on the H 2 CO maser and absorbtion lines of massive star formation regions, and the comparison with the results observed by the GBT (Robert C. Byrd Green Bank Telescope), it is shown that the results of frequency calibration are correct. Finally, by the OH maser observations in more than one hour toward W3(OH), and the methanol maser observations in more than 5 hours, it is found that the spectral profiles keep consistent, and the observational noise is consistent with the theoretical value, indicating the stability and reliability of the frequency calibration program. [ABSTRACT FROM AUTHOR]

The lunar rendezvous and docking (RVD) technology is an important guarantee for our third phase of lunar exploration. In this paper, by using VLBI (Very Long Baseline Interferometry) delay of CE03 (Chang'e-03) which was around the lunar, the changing of differential group delay (DGD) under the SBI (same-beam VLBI) observation mode was simulated. The simulation results indicated that the orbit distance between Orbiter and Ascender Combination (Ascender and Returner) was kept in 100 kilometers, and it lasted for half an hour, the track information of these two were well reflected by DGD which can be used for orbit determination. In the approach stage, DGD is rapidly approaching to 0, as Ascender Combination accelerated and closed to the orbiter, while the orbit distance was reduced from 5 km to 20 m, and was rapidly increased as Ascender Combination was far away from Orbiter. At last, using VLBI delay of CE03 which was halfway to the lunar, and transmitted two DOR (Differential One-Ranging) signals that were observed by CVN (Chinese VLBI Network), we calculated DPD (Differential Phase Delay), and preliminarily showed the error of DPD. [ABSTRACT FROM AUTHOR]

On 14th December 2013, the Chang’E-3 made a successful soft landing on the lunar surface, and then carried out the tasks of separating the lander and the rover, and taking pictures of each other. With the same beam VLBI (Very Long Baseline Interferometry) technique to observe the signals transmitted by the lander and the rover simultaneously, the differential phase delay between them is calculated, which can reflect the minor changes of the rover's position on a scale of a few centimeters. Based on the high sensitivity of differential phase delay, the rover's speeds during 5 movements are obtained with an average of 0.056 m/s. The relationship between the rover's shake in the moving process and the lunar terrain is analyzed by using the spectrum of the residual of the differential phase delay after the first-order polynomial fitting. [ABSTRACT FROM AUTHOR]