Doppler velocity of star (DVS)-aided strap-down inertial navigation system (SINS)-integrated navigation (SINS/DVS) is an effective method for correcting spacecraft velocity errors, but its navigation accuracy is significantly affected by the geometric distribution of navigation stars. To solve this problem, the effect of star geometry on the transmission of the measurement errors of DVS is studied, and the relationship between the geometric distribution of stars and spacecraft velocity error is derived based on the measurement model. The results show that velocity error is negative correlated with geometric distribution. Then, a star optimization strategy based on geometric distribution is proposed, and the calculation of the optimization index k is given. To verify the effectiveness of the newly proposed optimization strategy based on k, the performance of SINS/DVS-integrated navigation under a variety of navigation star groups is evaluated. The results show that the navigation error decreases with increasing k. When k is 0.4758, the velocity error is only 10.39% of that when k is 0.0021. Thus, k can be used as an evaluation index for optimizing the navigation stars of SINS/DVS-integrated navigation.

The multipath navigation using time delay between the direct and reflected solar oscillation is attractive in determining the spacecraft’s position. While its navigation accuracy relies significantly on the selection of the reflected body. To address this problem, factors related to the reflected body that may affect the navigation accuracy are identified first, according to the measurement model, including the magnitude of measurement (defined as t), the distance between the spacecraft to the reflected body (defined as |r rp_t r| ) and that to the Sun (defined as |r sp_t 0 ). Because the |r rp_t r| and |r sp_t 0| cannot be measured directly, the <SMP is introduced to describe the influence of them. Subsequently, the influence of t and <SMP on navigation accuracy is analyzed from the geometric perspective and simulations. The theoretical results indicate that the navigation error decreases with the reductions in t and <SMP, respectively. The simulations show that when the reflected body with the smallest t and

The atmospheric density error affects the accuracy of the Strap-down inertial navigation system (SINS)/Refraction celestial navigation system (RCNS) integrated navigation seriously by degrading the accuracy of the atmospheric refraction model. At present, the mechanism and extent of the impacts of atmospheric density error on measurements measurement models of SINS/RCNS integrated navigation are unclear. To solve this problem, this study first derives the relationship among atmospheric density error, measurements and measurement models (including refraction apparent height, refraction angle, and star pixel coordinates) of SINS/RCNS integrated navigation. Then, the quantitative relationship is provided based on it. The results show that 3.0% atmospheric density error can cause errors of 190.22 m in refraction apparent height measurement, 4.40" in refraction angle measurement model, and 0.13 pixels in star pixel coordinates measurement model. And these errors increase approximately linearly with the increase of atmospheric density error. Furthermore, simulations are carried out to verified the theoretical derivation and the linear relationship between the impacts of the atmospheric density error, which has a significant impact on position error and a relatively small impact on velocity error and posture error. When the atmospheric density error are 3.0%, 6.0%, and 9.0%, the position errors of the SINS/RCNS integrated navigation are about 1.4 times, 2.1 times, and 2.9 times of those without atmospheric density error. The research provides a theoretical basis for the elimination of the atmospheric density error.