Development of the Beidou Ionospheric Observation Network in China for space weather monitoring

The Global Navigation Satellite System (GNSS) beacon has been widely used in ionospheric monitoring. The Chinese Beidou Navigation Satellite System (BDS) started to operate in 2012, with three kinds of constellations: the medium Earth orbit, the inclined geosynchronous satellite orbit, and the geosynchronous Earth orbit. A compact, portable, and low-power GNSS observation instrument which is named BG2 GNSS ionospheric monitor was developed at the Institute of Geology and Geophysics, Chinese Academy of Sciences. It is capable of tracking BDS, Global Positing System, and Global Navigation Satellite System signals with a sampling rate up to 5 Hz. To use the unique BDS GEO signals for ionospheric monitoring, the Beidou Ionospheric Observation Network (BION) utilizing the BG2 GNSS ionospheric monitor was established recently in China with a total of 30 sites. This paper describes the development of the GNSS ionospheric monitor, the construction of the network, data processing, and preliminary scientific research. As demonstrated in the following paper, the BDS GEO total electron content data have shown unique value in some specific ionospheric studies due to the fact that it is not influenced by the mixed effect of spatial and temporal ionospheric variability as observed with other GNSS signals.