基于动力学轨道外推的星载辅助 GPS 快速搜索方法

摘要

Spaceborne GPS receivers are widely used for satellite real time navigation.While at least four visible GPS satellites are acquired,the GPS receiver can realize one location.However,most of the spaceborne GPS receivers still use the sequential search method and need to search all the GPS satellites because these receivers are moving fast and can't receive any assistant mes-sage from outside.The location costs too much time.In this paper,a spaceborne assisted GPS fast search method is proposed to re-duce the location time by decreasing the acquisition times.The method regards the satellite orbital motion as assistant information and predicts the approximate location based on the orbit extrapolation,and then judges the visibility of GPS satellite in real time by calculating the elevations.The spaceborne GPS receivers can acquire the visible GPS satellites preferentially so that the acquisition times decrease which leads to shorter location time.The simulation results prove that,compared with the sequential search method and decision -making tree search method,the spaceborne A -GPS fast search method needs least acquisition times for the same number visible GPS satellites,which increase most slowly with the increasing orbit height of spaceborne GPS receivers.%星载 GPS 接收机广泛应用于卫星实时导航定位、定时。只要捕获到至少4颗可见 GPS 卫星，GPS 接收机就能完成一次定位。但由于星载 GPS 接收机处于高动态运动状态，无法接收外界辅助信息，因此大部分星载 GPS 接收机仍然采用轮询搜索方法对所有 GPS 卫星进行捕获，导致定位时间长。在此背景下，提出一种星载辅助 GPS（AGPS）快速搜索方法，通过减少捕获次数来缩短定位时间。方法以卫星轨道运动规律为辅助信息，基于动力学轨道外推预测星载 GPS 接收机的概略位置，然后通过计算俯仰角实时判断 GPS 卫星对星载 GPS 接收机是否可见。星载 GPS 接收机可以优先捕获可见的GPS 卫星，从而减少捕获次数，缩短定位时间。仿真结果表明，相比于轮询搜索、决策树搜索方法，为搜索到相同颗可见GPS 卫星，星载辅助 GPS 快速搜索方法需要的捕获次数最少；并且，随着轨道高度增加，星载辅助 GPS 方法需要的捕获次数增加得最慢。