Abstract: To address the issue of the orbit determination of space targets when using space-based single line-of-sight meas-urement information a new observability index was established. The influence of higher-order perturbation terms on system observability and a single line-of-sight measurement orbit determination method were studied. Firstly, the sys-tem observability matrix was derived using the Lie derivative, the system observability index was obtained based on the locally weakly observable condition of the system, and the approximate formula for the observability of higher-order perturbation terms was derived. Secondly, under the assumption of a near-circular orbit, the relationship be-tween the orbit parameters of the space target and observation platform and the observability index was established, providing a basis for the design of the observation platform orbit. Thirdly, an iterative least squares orbit determination algorithm was proposed, and the orbit determination error covariance matrix was derived. The digital simulation re-sults indicated that the higher-order perturbation term improves the observability of the system by increasing the vec-tor heterohedrality, keeping the observation platform away from its ascending node ensures observability of the sys-tem, a large observability index causes high orbit determination accuracy, and the standard deviation of position esti-mation error is greatly affected by the observability of the system and the observation duration.

Key words: space-based single line-of-sight measurement, orbit determination, observability analysis, Lie derivative, iterative least squares