Abstract: The transmission link between BeiDou navigation satellites and user satellite, and the relationship between the capture sensitivity and the incoherent accumulation were analyzed. A fourtime incoherent accumulation was used and capture sensitivity reached -130dBm, together with positioning time less than 5 minutes. Based on the capture sensitivity, a STK model was set up to simulate the number of captured BeiDou navigation satellites for the user satellite whose orbit was of sun synchronous in a full orbital period. The results show that more than 4  satellites could be captured during the full orbital period. Positioning accuracy and speed accuracy are 2.59m and 0.00378m/s respectively. The first test of on-orbit satellite positioning was carried out right after BeiDou navigation satellite system completed deployment at the end of 2020. Six or more visible BeiDou navigation satellites were captured. Positioning accuracy of 2.77m and speed accuracy of 0.006m/s were achieved, showing good consistency with the simulated results. The study proves that the algorithm can be used for satellite positioning applications and  that it satisfies the positioning requirement based on Beidou navigation system.

Key words: BeiDou-3 navigation satellite system, incoherent accumulation, capture sensitivity, positioning accuracy, on-orbit test