The gravitational field model of an asteroid was presented through the utilization of spherical harmonic functions, and the kinetic equations governing the probe during its descent phase were methodically examined. An autonomous navigation framework employing dual artificial landmarks was introduced. Additionally, an observability examination was conducted on the condition number associated with the observation matrix. The dynamic precision, feasibility and effectiveness of the proposed dual artificial landmarks navigation approach for the probe were validated through simulations. These simulations showed that, in the absence of guidance control and under the influence of minimal gravitational and perturbative forces from the asteroid, the probe tended to deviate from the designated landing site following a spiral trajectory. Throughout the descent phase, the navigation strategy leveraging artificial landmarks, optimized via real-time minimization of the observation matrix’s condition number, exhibited superior accuracy compared to approaches that maximize the condition number. This outcome substantiates the validity of the observability analysis predicated on the observation matrix’s condition number.