Recently, the Very Long Baseline Interferometry (VLBI) operation team at the Nanshan Station of Xinjiang Astronomical Observatory (XAO) ,Chinese Academy of Sciences, operated the NanShan 26-meter Radio Telescope (NSRT) to participate in 4-Gbps VLBI observations organized by the European VLBI Network (EVN). Fringes were successfully found when broad-band data were correlated on March 11, 2024. Compared with previous 2-Gbps observations, 4-Gbps observations could allow radio astronomers to improve VLBI image sensitivity by a factor of about 1.4.

VLBI is a state-of-art interferometry technique. It can combine electromagnetic signals from radio telescopes around the world and enable astronomers to reveal some fine radio structures of distant radio sources with an image resolution of up to tens of micro-arcseconds. Such an extremely high-resolution image technique can also enable astronomers to capture the first image of the black shadow in the galaxy M87. Moreover, VLBI plays a key role in defining the International Celestial Reference Frame (ICRF) for deep-space navigation.

The broad-band test observations were performed with the upgraded digital backend DBBC2 and the new data recorder Flexbuff at the Nanshan station. The observations used 16 sub-bands per polarization, 32-MHz filters and 2-bit quantization.

The NSRT was built in 1991 with a 25-m aperture. In 2014-2015, the telescope was fully upgraded and re-commissioned. The NSRT is located in the hinterland of Eurasia. Its unique location and advanced VLBI system make it play an irreplaceable role in the East Asian VLBI Network (EAVN) and the EVN. As a core member of the Chinese VLBI Network (CVN), NSRT also participated in the accurate orbit determinations of the Chang’e lunar missions and the Mars exploration program.

As a member of the EVN, the NSRT serves EVN observations for three sessions per year, in total of about 750 hours. Currently, it has just completed the EVN session one of 2024. The success of the 4-Gbps testing observations indicates that the Nanshan station has entered the broadband VLBI era.