Highly elliptical orbit satellite integrated navigation method using celestial/radar altimeter

In order to realize autonomous navigation of highly elliptical orbit satellite, an integrated navigation system based on celestial and radar altimeter navigation method is proposed. Since the dynamics of highly elliptical orbit satellite changes severely around perigee, the precision of celestial navigation method based on star-earth angle observation declines seriously. Though the orbit height can be measured by radar altimeter, the measuring range is less than 1000 km due to the limitation of size and power. To make full use of the methods, the integrated navigation system is composed by both the celestial and radar altimeter methods, and the UKF algorithm is used to estimate the navigation information. When the satellite is near the perigee and the height is below 1000 km, the radar altimeter measurement is introduced as additional observation to celestial navigation. When the satellite is near the apogee, only the celestial navigation method is used in navigation process. Simulation results show that the proposed integrated navigation method can make full use of the two navigation methods, and achieve autonomous and continuous navigation information outputs. The navigation precision is increased 68.9% compared with that only by celestial navigation.