Objective  Celestial navigation is an important method of autonomous navigation. Astronomical observation of high-speed aircraft will be disturbed inevitably by the high-speed flow nearby the observation window, which causes the star maps degradation like displacement and blurring. And this will lead to a decrease in the accuracy of the stars center, which will have a direct effect on the accuracy of astronomical attitude determination. At present, most studies on the calculation and correction of star map degradation are based on computer simulation, whose results are greatly affected by the configuration of model parameters and may not be consistent with the real physical process. Therefore, it is necessary to construct the physical experimental observation conditions of the influence of high-speed flow on star-light deflection and to carry out experimental research.

  Methods  A small static wind tunnel is built, which can generate a Mach 2.5/3.5 mixing layer structure in the test section. The calibrated simulated star-points on the indoor dome with a diameter of 10 m are measured through the high-speed flow, and the star centroids are extracted to collect the data of imaging displacements by the real flow. The data of star image disturbed by the flow field are obtained and compared with the computer simulation results.

  Results and Discussions   The deflection by flow is greater than the estimated value of computer simulations. At the near end of the tunnel nozzle, the high-speed mixing layer makes a large star-light deflection. The mean deflection in the vertical direction of the flow field is less than 0.5″, and that in the direction of the flow field is 3.85″, and the maximum is close to 4.89″ (Fig.8). At the far end, the mean deflection in these two direction is −1.36″ and −0.49″ respectively (Fig.9). The variation of starlignt deflection at the near end is smaller and more stable than that at the far end, which is conducive for modeling correction (Fig.10).

  Conclusions  A star-points observation system under the high-speed flow was constructed based on the indoor dome, and a Mach 2.5/3.5 mixed high-speed flow field was generated in the experimental observation section. The target star-points were observed from different observation positions, and the quantitative conclusion of the high-speed flow on star-points imaging disturbance was obtained for the first time by physical observation experiment. 　　The results show that: 1) Star-light deflection is mainly concentrated in streamwise. This result is consistent with the expectation of the theoretical analysis; 2) The star-light deflection caused by the flow field at the near end of the nozzle is larger than that at the far end, but the variation range is smaller and more stable than that at the far end, which is conducive for modeling correction; 3) The absolute value of target starlight deflection caused by high-speed mixed flow is greater than the simulation result at both near and far end of the tunnel nozzle. The current work has proved the stability and effectiveness of the experimental system, which can provide an experimental basis to form a systematic understanding of the influence of flow structure on navigation starlight acquisition by the subsequent systematic observation under different altitude angles and azimuth angles, and provide experimental data of physical observation for simulation modeling. Then, a modified model of the influence of high-speed flow fields with different structures on starlight could be established, which may provide theoretical support for the suppression of aerodynamic influence and the deflection correction of air-cooled film in the astronomical observation of hypersonic vehicles.