中文摘要：

本文提出采用星载GPS双差定轨计算编队卫星星间基线的方法。利用2005年12月7日到16日的GRACE实测数据进行了编队卫星双差定轨计算，采用KBR观测数据对本文双差定轨结果和JPL非差定轨结果进行了外部检核，通过与JPL非差定轨结果比较，表明本文提出的双差定轨方法可以明显提高编队卫星的星间基线精度，在距离小于100km情况下，GRACE卫星星间基线精度优于2．0mm。

英文摘要：

The method of computing the baseline length between formation flying satellites using onboard GPS doubly differ- enced （DD） precise orbit determination （POD） is put forward. The baseline length between two GRACE satellites are computed by using the GPS data observed from December 7 to 16, 2005. The results of our DD POD and the orbits of JPL which are compu- ted using Zero Differenced （ZD） GPS data are compared independently with k -band ranging （KBR） data. Compared with the results of JPL ZD POD, the precision of relative positioning of satellites can be improved significantly by using the method of DD POD. The precision of the baseline length between two GRACE satellites is better than 2.0mm when the baseline is less than 100 km long.