A celestial navigation system (CNS) can be integrated in vehicles to suppress the diverging error of the inertial navigation system (INS). However, the CNS is subjected to aero-thermo-optic effects in hypersonic environments that introduce large-scale centroiding errors in star sensor images and greatly reduce the star sample size, limiting the usefulness of the CNS for hypersonic vehicles. In this study, these difficulties were addressed by the development of a statistical model for measurement noise based on the angular distance so that the standard deviation of the measurement noise can be correlated with the star sample size. To compensate for the centroiding error, a variable-dimension pseudo-transient adaptive filter was designed where the initial R matrix is set according to the star sample size. A semi-physical experiment was conducted to evaluate the performance of the proposed method, and the results indicated that stable centroiding error compensation was achieved for extremely small star sample sizes. In particular, the proposed method compensated for up to 66.24% of random positioning error, which is a performance improvement of about 10% compared with conventional compensation methods.

A high power and high quality picosecond laser is crucial in MEMS fabrication regarding micromachines. Optimal seed beam coupling is an important precondition to enhance laser efficiency. However, empirical coupling limits its development. In this paper, the physical parameters related to coupling are determined. The relationships among them are established under optical mode matching constraints to satisfy optimal seed beam coupling. According to a theoretical analysis, the focal length cut-off and the optimal coupling position of the coupling lens are acquired. A maximum transmittance of 87.2% is acquired with a 6 W input seed power in the validation experiment. In further power amplification experiments, a diffraction-limited beam quality is achieved, with M²_X = 1.111, M²_Y = 1.017, an optical efficiency of 60.5% and a slope efficiency of 66%, benefiting from the previous theoretical guidance.