Estimate of Frequency Bias Method in DORIS Real-time Orbit Determination

DIODE is a real-time on-board orbit determination software,embedded in the DORIS receiver since 1998.Frequency biases between beacons and satellites USO are the max errors in DORIS measurement data.The purpose of this paper is to find a method to estimate the frequency biases.To start with,we describe the state and measurement equations about DORIS real-time orbit determination.Then,we present a method to estimate the frequency biases.Using our method and considering the 40×40 Earth gravitational fields,solid tide,moon and sun attractions,we analyze ten days' measurements data of SPOT-5.The results show that the radial component RMS is better than 30 cm,which correspond to the SPOT-5 real time orbit accuracy,and the 3D RMS is better than 80 cm,which achieves the specifications of SPOT-5.