Research On Position Determination For Spacecraft Based On TDOA Measurement Of Pulsar

Pulsar is a kind of neutron star with rapid self-rotation. The signal it radiates has stable and precise period, which is the most remarkable property. The property can offer position, velocity, and accurate time navigation information for the spacecrafts in near-earth orbit, geostationary orbit, elliptic orbit or interplanetary orbit. Therefore, X-ray pulsar navigation has an extremely important military use and wide application prospect.This thesis studies the technology of orbit determination for spacecraft based on TDOA measurement. TDOA measurement, a key technology in XPNAV system, decides the precision of XPNAV's timing and position determination. After giving the formula of Pulse TDOA measurement, the influences from Doppler delay effect, Parallax and Sun-Shapiro delay effect on the measurement precision of TDOA are analyzed in the paper. Then, the Navigation algorithms, EKF and SR-UKF are introduced, which are used to determinate position for spacecraft. Finally, simulation results show that using the formula of pulse TDOA measurement corrected as observation equation can improve the positioning accuracy for spacecraft. Obviously, we obtain that using SR-UKF in X-ray pulsar-based position determination can improve the positioning accuracy from simulation result, and its precision is better than using EKF.