Integration of very long baseline interferometry data acquisition, recording, and transmission with multichannel and multibit for CE-5 mission

Abstract

<p indent="0mm">Real-time signal acquisition, recording, and transmission are the important functions of very long baseline interferometry (VLBI). In the Chang’e-5 (CE-5) mission, a VLBI backend is required to connect the telemetry, track and command (TT&amp;C) beacons, data signals from multiple probes, such as the orbiter, ascender, and lander, and signals from the extragalactic radio source in time. Due to the multiple frequency points, large dynamic range, and complex spectrum form of the probe signals, existing VLBI astronomical backends do not meet the requirements of lunar exploration and deep space exploration. According to the characteristics of the beacon of CE-5 probes, we researched the integration technology of multichannel and multibit signal acquisition, recording, and transmission. This paper proposes a frequency tunable polyphase-filter bank algorithm, which can flexibly set frequency and obtain flat amplitude and linear phase characteristics in a wide band. The novel integrated VLBI backend developed by this technology contains 16 channels, which can sample and record all the TT&amp;C and data signals from CE-5 probes in real time and transmit the VLBI data to the VLBI center through the network. It ensures successful VLBI measurement in the complex electromagnetic environment of CE-5 multi beacons. Compared with the previous astronomical backends, the real-time performance, measurement accuracy, and reliability of the novel integrated VLBI backend are greatly improved, which support the successful completion of China’s first lunar sampling return mission of CE-5. The novel integrated VLBI backend also has the function of multibit quantization to meet the needs of wide and narrow observation of future radio sources and probes.