Analysis of Vector Tracking Loop Algorithm Combine ISL & GNSS Signal for High orbit spacecraft Positioning

On the high earth orbit, traditional Global Navigation Satellite System (GNSS) downlink signals are very weak, visible satellites are quite few and geometry structure is poor. In this article, the inter-satellite link (ISL) signal is taken into used to assist GNSS weak signals for high orbital space vehicle positioning. The vector delay lock loop (VDLL) tracking algorithm are used for combining the ISL strong signal branch and the traditional weak signal branches, and overcoming the fault of biased VDLL tracking results. The theory analysis and numerical simulation results prove that the GNSS signals tracking assisted with ISL is unbiased. The conclusion indicates the VDLL tracking algorithm combining ISL signal with GNSS signal are effective.