Pulsar navigation using time of arrival (TOA) and time differential TOA (TDTOA)

Pulsar navigation is a novel autonomous navigation method for deep-space missions. The pulsar navigation method using the time of arrival (TOA) determines the absolute position of the spacecraft. However, its accuracy is greatly affected by system errors, including the ephemeris error of the pulsar and the satellite-borne clock error. The time differential technique is an innovative method to eliminate these system errors. However, pulsar navigation using time differential TOA (TDTOA) can only provide an accurate relative position, and the absolute position is missing. To solve the problem, pulsar navigation using both TOA and TDTOA is proposed in this paper. Because the measurement of pulsar navigation using TDTOA is not only related to the current state vector but to the previous state vector. The previous state vector is replaced with its estimation, and the covariance matrix of the measurement noise is also derived. Simulations show that the accuracy of the new proposed pulsar navigation method is better than that only using TOA or TDTOA. Besides, the impact factors of the new proposed method are analyzed by simulations.