5.9 Future of Navigation Satellite System
401
navigation, but also directly promote the interdisciplinary researches, such as physics,
astronomy, geophysics, mechanical engineering, information & communication
engineering, control science and engineering, electronic science and technology,
instrument science and technology, aeronautic & astronautic science and technology,
surveying & mapping science and technology, nuclear science and technology, as
well as computer science and technology. In addition, some basic research fields
like the gravitational wave detection using the X-ray pulsars may also be carried
out. It is conducive to accelerating the interdisciplinary integration researches, well
developing and utilizing pulsar resources, improving the research ability and level
of basic, cutting-edge and exploratory disciplines, and promoting the development
of human civilization and the scientific and technological progress.
5.9.2 Generation Gap Between Navigation Satellite Systems
It is well known that a typical navigation satellite system consists of three segments,
including space constellation, ground control and user terminal, where the space
constellation segment is composed of tens of navigation satellites evenly distributed
in the MEO, GEO or IGSO, providing more than four-signal coverage for global or
regional users; the ground control segment is composed of the monitoring, major
control and injection stations, which is responsible for tracking and monitoring the
navigation satellites, compiling the control instructions and navigation messages,
and uploading them to the navigation satellites regularly; the user terminal segment
is composed of all kinds of user receivers on the Earth’s surface and in the near-earth
orbits, which is responsible for receiving and processing the signals from the navigation satellites to provide the position and time parameters for users. In general, the
information transmission system between the navigation constellation segment and
the ground control segment is referred to as TT&C mechanism, and the information transmission system between the navigation constellation segment and the user
terminal segment is referred to as navigation mechanism. Obviously, the current
navigation satellite system contains two aspects of the TT&C mechanism and the
navigation mechanism, as shown in Fig. 5.45.
From the perspective of the development of navigation satellite system, the passive
navigation mechanism based on the principle of the Doppler shifts is adopted for the
First Generation Navigation Satellite Systems (1G-NAV), such as the Transit navigation system built in the United States in 1964, and the Tsiklon and Parus system built
in Soviet Union in 1970 s. In addition, the active navigation mechanism based on the
two-way timing and ranging is adopted for the 1G-NAV of China, i.e., the BeiDou
navigation satellite test system built in 2000. At present, the passive navigation
systems with one-way time ranging are adopted in the Second Generation Navigation
Satellite Systems (2G-NAV), such as U.S. GPS system, Russian GLONASS system,
China’s BeiDou system and Europe’s Galileo system. Obviously, the essential difference between the 1G-NAV and 2G-NAV is to use the different navigation mechanism,
401
navigation, but also directly promote the interdisciplinary researches, such as physics,
astronomy, geophysics, mechanical engineering, information & communication
engineering, control science and engineering, electronic science and technology,
instrument science and technology, aeronautic & astronautic science and technology,
surveying & mapping science and technology, nuclear science and technology, as
well as computer science and technology. In addition, some basic research fields
like the gravitational wave detection using the X-ray pulsars may also be carried
out. It is conducive to accelerating the interdisciplinary integration researches, well
developing and utilizing pulsar resources, improving the research ability and level
of basic, cutting-edge and exploratory disciplines, and promoting the development
of human civilization and the scientific and technological progress.
5.9.2 Generation Gap Between Navigation Satellite Systems
It is well known that a typical navigation satellite system consists of three segments,
including space constellation, ground control and user terminal, where the space
constellation segment is composed of tens of navigation satellites evenly distributed
in the MEO, GEO or IGSO, providing more than four-signal coverage for global or
regional users; the ground control segment is composed of the monitoring, major
control and injection stations, which is responsible for tracking and monitoring the
navigation satellites, compiling the control instructions and navigation messages,
and uploading them to the navigation satellites regularly; the user terminal segment
is composed of all kinds of user receivers on the Earth’s surface and in the near-earth
orbits, which is responsible for receiving and processing the signals from the navigation satellites to provide the position and time parameters for users. In general, the
information transmission system between the navigation constellation segment and
the ground control segment is referred to as TT&C mechanism, and the information transmission system between the navigation constellation segment and the user
terminal segment is referred to as navigation mechanism. Obviously, the current
navigation satellite system contains two aspects of the TT&C mechanism and the
navigation mechanism, as shown in Fig. 5.45.
From the perspective of the development of navigation satellite system, the passive
navigation mechanism based on the principle of the Doppler shifts is adopted for the
First Generation Navigation Satellite Systems (1G-NAV), such as the Transit navigation system built in the United States in 1964, and the Tsiklon and Parus system built
in Soviet Union in 1970 s. In addition, the active navigation mechanism based on the
two-way timing and ranging is adopted for the 1G-NAV of China, i.e., the BeiDou
navigation satellite test system built in 2000. At present, the passive navigation
systems with one-way time ranging are adopted in the Second Generation Navigation
Satellite Systems (2G-NAV), such as U.S. GPS system, Russian GLONASS system,
China’s BeiDou system and Europe’s Galileo system. Obviously, the essential difference between the 1G-NAV and 2G-NAV is to use the different navigation mechanism,