Fringe Detection in the Lunar Orbit VLBI Experiment: The Initial Clock Search

Abstract We present the design and implementation of a fringe detection pipeline for the Lunar Orbit VLBI Experiment (LOVEX) on board China’s Queqiao-2 cislunar relay satellite. To address the challenge posed by limited space–ground time synchronization accuracy, we developed a dedicated initial clock offset search scheme based on a modified version of the Chinese VLBI Network software correlator. Key features of the pipeline include raw data validation, wide-range clock offset search, iterative fringe fitting, and GPU-accelerated processing. The pipeline was successfully applied to the initial clock offset determination in LOVEX observations. In particular, we report the detection of fringes for blazar AO0235+164 in the s5123m session, where a projected baseline length of 5.5 Earth diameters was achieved. We further discuss technical approaches for enhancing sensitivity to weak signals, with an emphasis on the need for advanced phase calibration techniques. The potential application of tensor core acceleration is also discussed.