arXiv subjects

Jin-song Ping

Publications and source records attributed to Jin-song Ping.

2 recordsLinked to original sources

arXiv2025

Noise Reduction Method for Radio Astronomy Single Station Observation Based on Wavelet Transform and Mathematical Morphology

The 21 cm radiation of neutral hydrogen provides crucial information for studying the early universe and its evolution. To advance this research, countries have made significant investments in constructing large low-frequency radio telescope arrays, such as the Low Frequency Array (LOFAR) and the Square Kilometre Array Phase 1 Low Frequency (SKA1-low). These instruments are pivotal for radio astronomy research. However, challenges such as ionospheric plasma interference, ambient radio noise, and instrument-related effects have become increasingly prominent, posing major obstacles in cosmology research. To address these issues, this paper proposes an efficient signal processing method that combines wavelet transform and mathematical morphology. The method involves the following steps: Background Subtraction: Background interference in radio observation signals is eliminated. Wavelet Transform: The signal, after removing background noise, undergoes a two-dimensional discrete wavelet transform. Threshold processing is then applied to the wavelet coefficients to effectively remove interference components. Wavelet Inversion: The processed signal is reconstructed using wavelet inversion. Mathematical Morphology: The reconstructed signal is further optimized using mathematical morphology to refine the results. Experimental verification was conducted using solar observation data from the Xinjiang Observatory and the Yunnan Observatory. The results demonstrate that this method successfully removes interference signals while preserving useful signals, thus improving the accuracy of radio astronomy observations and reducing the impact of radio frequency interference (RFI).

astro-ph.IM↗

arXiv2015

Ionospheric inversion of the Venus Express radio occultation data observed by Shanghai 25 m and New Norcia 35 m antennas

Electron density profiles of the Venus' ionosphere are inverted from the Venus Express (VEX) one-way open-loop radio occultation experiments carried out by Shanghai 25 m antenna from November 2011 to January 2012 at solar maximum conditions and by New Norcia 35 m antenna from August 2006 to June 2008 at solar intermediate conditions. The electron density profile (from 110 km to 400 km) retrieved from the X-band egress observation at Shanghai station, shows a single peak near 147 km with a peak density of about $2 \times 10^4 \rm{cm}^{-3}$ at a solar zenith angle of 94$^{\circ}$. As a comparison, the VEX radio science (VeRa) observations at New Norcia station were also examined, including S-, X-band and dual-frequency data in the ingress mode. The results show that the electron density profiles retrieved from the S-band data are more analogous to the dual-frequency data in the profile shape, compared with the X-band data. Generally, the S-band results slightly underestimate the magnitude of the peak density, while the X-band results overestimate that. The discrepancy in the X-band profile is probably due to the relatively larger unmodeled orbital errors. It is also expected that the ionopause height is sensitive to the solar wind dynamical pressure in high and intermediate solar activities, usually in the range of 200 km - 1000 km on the dayside and much higher on the nightside. Structural variations ("bulges" and fluctuations) can be found in the electron density profiles in intermediate solar activity, which may be caused by the interaction of the solar wind with the ionosphere. Considerable ionizations can be observed in the Venus' nightside ionosphere, which are unexpected for the Martian nightside ionosphere in most cases.

physics.space-ph↗