Abstract: To capture weak navigation signals from the opposite side of the Earth, receivers operating in geostationary orbit and higher altitudes must use long coherent integration time. However, the application of long coherent integration time leads to an excessive number of search units during signal acquisition. For high orbit receivers, the probability of receiving the main lobe signal from a navigation satellite is relatively high. When the receiver captures the strong signal from the main lobe (referred to as a strong satellite), the acquisition efficiency and accuracy are much higher than when capturing the weak signal from a side lobe (referred to as a weak satellite). Thus, a rapid signal recapture algorithm using a strong satellite to assist weak satellites is proposed. Firstly, the position error pattern of the high orbit receiver during the loss-of-lock period is analyzed and the range of the pseudo-range estimation error from the receiver to the weak satellite is derived. Then, assuming that the receiver has already captured a main lobe signal, the distance constraint between the receiver and the captured satellite is used to reduce the receiver's position uncertainty, thereby narrowing the range of the pseudo-range estimation error for the satellite to be captured and reducing the number of code phase search units. Theoretical analysis and simulation results show that, with the assistance of a strong satellite, the code phase search range for capturing a weak satellite is reduced by more than 50% on average, and the reduction is inversely proportional to the sine value of the angle between the line-of-sight vectors of the strong and weak satellites. Furthermore, the higher the receiver's orbit, the smaller the average angle between the line-of-sight vectors of the strong and weak satellites, and the better the compression effect on the weak satellite's code phase search range. This method can significantly improve the efficiency of signal re-acquisition for high orbit receivers and enhance their autonomous navigation capabilities.

Key words: high orbit receiver, signal recapture, main-lobe signal, side-lobe signal, code phase range compression