Satellite To Expand The Applications Of Gps In The Formation Of The Constellation Status To Determine

The Global Positioning System (GPS) will play the important role in relative position and attitude determination for satellites formation flying However, in deep space, GPS may not be sufficient to reliably determine the relative position and attitude of formation flying In this paper, determination of the relative states of formation satellites using onboard augment GPS was investigated. Autonomous Formation Flyer technology developed by JPL is used Three receiving antennas and one transmitting antenna are installed on each satellite Each of satellites can transmit analog GPS signal but more accuracy. The multiple receiving antennas on the every satellite are capable of acquiring precise pesudorange and carrier phase signals transmitted by other satellite and compose of a kind of onboard augment GPS system. Based on that, we primarily discussed the special problems in autonomy positioning of satellite's formation flying.Firstly, the visibility on space target observing GPS was analyzed. Secondly the basic principle and the measurement model of AFF were developed. Lastly, determination of the relative states of two special formations with AFF configure was researched and simulation results are analyzed.Because geometry of formation of two satellites is very weak, the solution covariance is very big and unstable In order to resolve this problem, the measurement model was transformed from Cartesian coordinate system to Sphere coordinate system. It should be found that in Sphere coordinate system the solution covariance is stable and can be used to a simulation/covariance analysis. This method of coordinate system transformation we developed in the paper may give a new way to solve the abnormal equations.Using carrier phase, the first challenge is determining initial phase bias. Because formation satellite's relative position is very close and the geometry can change easily, based on the relative motion of satellites, the initial phase bias could be quickly resolved Simulation solution indicates that phase bias can be determined quickly and the relative states accuracy should be improved by using initial phase bias.