5.9 Future of Navigation Satellite System
405
If the navigation constellation can operate autonomously for a long time, the
TT&C mechanism of navigation satellite system will change essentially. So, the
autonomous navigation will become the development orientation of the 3G-NAV
system, which can effectively enhance the anti-jam and autonomous survival ability
of the navigation satellite system and reduce the dependence of the system on
the ground TT&C stations, with great engineering application value and strategic
research significance.
5.9.3 Conception of Third-Generation Navigation Satellite
System
The essential difference between the 1G-NAV and 2G-NAV is the difference of using
the navigation mechanism, while the difference between the 2G-NAV and 3G-NAV
is the difference of using the TT&C mechanism. So, the 3G-NAV is defined as a
kind of the navigation satellite system built by using the space-based TT&C mechanism, which can provide long-term autonomous operation service for the navigation
constellation.
In the numerical analysis experiment in Sect. 5.7.5, the autonomous navigation
of navigation constellation is achieved by installing the X-ray detectors on each
navigation satellite platform to detect the X-ray photons radiated from the pulsars,
measuring the pulse arrival-time and getting the pulsar’s image information, as well as
autonomously determining the orbit, time and attitude parameters of each satellite.
However, the X-ray photon fluxes radiated from the pulsars are very so low and
weak that the detector system with an array of large area is required to install on the
platform of satellite for collecting the X-ray photons, while the detector system is
often with a large volume, heavy weight and high power consumption, resulting in
that the limited resource allocation of the satellite’s payload is crowded out. From
the perspective of the development of current X-ray detector technology, it is still
difficult to develop the navigation-type detectors with high sensitivity, small size,
light weight and low power consumption, which is suitable for the application of
satellite’s platform. For this reason, the constellation composed of several small or
medium-sized satellites is constructed in the LEO, known as reference constellation,
where the X-ray detector system is the only pay load of each satellite, with the
effective detection area of 1−10 m
2 , which is called database-type detectors. Taking
the X-ray signals radiated from the pulsars as natural beacons, the satellites of the
reference constellation autonomously determine the navigation parameters like orbit,
time and attitude. Meanwhile, taking the reference constellation satellites as the
TT&C stations with dynamically-accurately known positions, the orbit and time
parameters of the GNSS satellites can be determined in real time by receiving the
navigation signals emitted from them, and then the navigation messages are compiled
and transmitted to the GNSS satellites through the inter-satellite links between the
satellites in the reference constellation and those in the GNSS constellation. In this
405
If the navigation constellation can operate autonomously for a long time, the
TT&C mechanism of navigation satellite system will change essentially. So, the
autonomous navigation will become the development orientation of the 3G-NAV
system, which can effectively enhance the anti-jam and autonomous survival ability
of the navigation satellite system and reduce the dependence of the system on
the ground TT&C stations, with great engineering application value and strategic
research significance.
5.9.3 Conception of Third-Generation Navigation Satellite
System
The essential difference between the 1G-NAV and 2G-NAV is the difference of using
the navigation mechanism, while the difference between the 2G-NAV and 3G-NAV
is the difference of using the TT&C mechanism. So, the 3G-NAV is defined as a
kind of the navigation satellite system built by using the space-based TT&C mechanism, which can provide long-term autonomous operation service for the navigation
constellation.
In the numerical analysis experiment in Sect. 5.7.5, the autonomous navigation
of navigation constellation is achieved by installing the X-ray detectors on each
navigation satellite platform to detect the X-ray photons radiated from the pulsars,
measuring the pulse arrival-time and getting the pulsar’s image information, as well as
autonomously determining the orbit, time and attitude parameters of each satellite.
However, the X-ray photon fluxes radiated from the pulsars are very so low and
weak that the detector system with an array of large area is required to install on the
platform of satellite for collecting the X-ray photons, while the detector system is
often with a large volume, heavy weight and high power consumption, resulting in
that the limited resource allocation of the satellite’s payload is crowded out. From
the perspective of the development of current X-ray detector technology, it is still
difficult to develop the navigation-type detectors with high sensitivity, small size,
light weight and low power consumption, which is suitable for the application of
satellite’s platform. For this reason, the constellation composed of several small or
medium-sized satellites is constructed in the LEO, known as reference constellation,
where the X-ray detector system is the only pay load of each satellite, with the
effective detection area of 1−10 m
2 , which is called database-type detectors. Taking
the X-ray signals radiated from the pulsars as natural beacons, the satellites of the
reference constellation autonomously determine the navigation parameters like orbit,
time and attitude. Meanwhile, taking the reference constellation satellites as the
TT&C stations with dynamically-accurately known positions, the orbit and time
parameters of the GNSS satellites can be determined in real time by receiving the
navigation signals emitted from them, and then the navigation messages are compiled
and transmitted to the GNSS satellites through the inter-satellite links between the
satellites in the reference constellation and those in the GNSS constellation. In this