5.9 Future of Navigation Satellite System
399
Fig. 5.44 Application system of XPNAV
various fields of national economy. At present, the application of the GNSS has
become a necessary part of people’s work and life. If the navigation constellation
can achieve the autonomous navigation, the workload of ground TT&C system will
be reduced effectively, the number of the deployed TT&C stations and the number of
injecting the messages from the ground stations to the navigation satellites reduced,
the construction and long-term operation maintenance cost of the navigation constellation reduced, the integrity of navigation information monitored in real time, and the
dependence of the navigation constellation on ground TT&C system reduced, so as to
enhance the autonomous survivability of the navigation satellite system. Currently,
the navigation constellations themselves need frequent information support from
the ground control system every day, so that they cannot operate independently for
a long time in the case without the ground support. The autonomous navigation
technology of navigation constellation based on the cross-link information has the
problem that the whole rotation errors of the constellation accumulate with time,
so that it is difficult for the constellation to run autonomously for a long time. The
autonomous navigation of navigation satellites based on the X-ray pulsars has not the
whole rotation of the constellation and can realize the autonomous operation of the
constellation with high precision for a long time, which is in the line with the development trends of seamless and high-precision autonomous navigation application
for the spacecrafts orbiting the Earth. Therefore, speeding up the development of the
399
Fig. 5.44 Application system of XPNAV
various fields of national economy. At present, the application of the GNSS has
become a necessary part of people’s work and life. If the navigation constellation
can achieve the autonomous navigation, the workload of ground TT&C system will
be reduced effectively, the number of the deployed TT&C stations and the number of
injecting the messages from the ground stations to the navigation satellites reduced,
the construction and long-term operation maintenance cost of the navigation constellation reduced, the integrity of navigation information monitored in real time, and the
dependence of the navigation constellation on ground TT&C system reduced, so as to
enhance the autonomous survivability of the navigation satellite system. Currently,
the navigation constellations themselves need frequent information support from
the ground control system every day, so that they cannot operate independently for
a long time in the case without the ground support. The autonomous navigation
technology of navigation constellation based on the cross-link information has the
problem that the whole rotation errors of the constellation accumulate with time,
so that it is difficult for the constellation to run autonomously for a long time. The
autonomous navigation of navigation satellites based on the X-ray pulsars has not the
whole rotation of the constellation and can realize the autonomous operation of the
constellation with high precision for a long time, which is in the line with the development trends of seamless and high-precision autonomous navigation application
for the spacecrafts orbiting the Earth. Therefore, speeding up the development of the