Accuracy evaluation of Doresa and Milena Galileo satellites broadcast ephemerides

摘要

On 22 August 2014 Doresa and Milena Galileo satellites were launched in wrong orbit. In November 2014 European space agency started a salvaged mission to make two satellites usable. On 5 August 2016 these two satellites started broadcasting ephemerides in navigation message for testing purposes. Any errors in these ephemerides will directly impact the accuracy of Galileo positioning. This paper compares all the Galileo satellites position computed using broadcast ephemerides with the precise position provided by the IGS with a focus on Doresa and Milena satellites. The comparison was undertaken every second during 20 days of data. The statistics of these errors were also analyzed. The position error between the broadcast orbit and the IGS precise orbit was determined for each second for the period starting on February 21, 2018 (DOY 52) to March 12 (DOY 71) by using IGS products. The analysis shows that the broadcast orbit of Doresa and Milena satellite has a daily 3d RMS error of about 2 meters that is a comparable value with that of the other Galileo satellites. Only on DOY 62 they show an RMS 3d error of about 40 meters.