4.8 Ground Navigation Networks for Spacecrafts
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the monitor stations, master control stations and injection stations (also known as
the dedicated ground antennas). The monitor stations take charges of tracking and
measuring all GPS satellites passing over the stations, obtaining the pseudorange,
carrier phase and navigation message, measuring the atmospheric parameters like
temperature, humidity and air pressure, and finally transmitting all data to the master
station for processing. Using the measurement data from the monitor stations, the
master station takes charges of calculating the precise orbits and clock biases of
the GPS satellites, forming the navigation messages and commands for the GPS
satellites, and finally transmitting them to the injection stations. Through the S-band
antennas, the injection stations take charges of injecting the navigation messages and
commands to the GPS satellites, and receiving the telemetry information sent by the
satellites.
Since beginning to form the GPS constellation in 1978, as to April 2020, there
are a total of 74 GPS satellites with 7 types launched, including 11 Block I, 9 Block
II, 19 Block IIA, 13 Block IIR, 8 Block IIR-M, 12 Block IIF and 2 Block III. With
the GPS satellites’ modernizing, the optimized constellation operating and the User
Ranging Error (URE) decreasing, the performance of the GPS system is improved
gradually. In order to support the evolution of the platform and payload technologies
of GPS satellites, it is required to continuously improve the ground control network.
The development of ground control network for GPS constellation is divided into
the following four phases.
(1) From 1978 to 1985 was the demonstration phase. The ground closed-loop
control network was initially set up to support the on-orbit operation of GPS
Block I satellite series mainly through manual operation.
(2) From 1985 to 2007 was the full-constellation operation phase. The first generation of ground control segment with basic network architecture was built,
which has the capability to support the coordinated operation of 10 network
nodes to ensure the on-orbit operation of GPS Block II, IIA, IIR and IIR-M
satellite series.
(3) From 2007 to 2016 was the capability-improved phase. The second-generation
ground control segment with a network architecture facing users was built,
which can support more than 10 users of network nodes, to ensure the onorbit operation of the modernized GPS satellites, such as Block IIR-M and IIF
satellite series.
(4) From 2016 entered the new capability-upgraded phase. The Next-Generation
Operational Control System (OCX) will be built, with the network architecture
of central interface, modularization, flexibility and expandability, and the capability of supporting more than 100 network node users, to ensure the on-orbit
operation of current GPS satellites and transit to the TT&C tasks of the GPS
III satellites.
The GPS OCX will dramatically enhance GPS command, control and mission
capabilities and provide significant benefits to military and civilian users around the
world, and its development is following an incremental approach, with three versions
of Block-0, Block-1 and Block-2. The Block-0 is the launch and control system
255
the monitor stations, master control stations and injection stations (also known as
the dedicated ground antennas). The monitor stations take charges of tracking and
measuring all GPS satellites passing over the stations, obtaining the pseudorange,
carrier phase and navigation message, measuring the atmospheric parameters like
temperature, humidity and air pressure, and finally transmitting all data to the master
station for processing. Using the measurement data from the monitor stations, the
master station takes charges of calculating the precise orbits and clock biases of
the GPS satellites, forming the navigation messages and commands for the GPS
satellites, and finally transmitting them to the injection stations. Through the S-band
antennas, the injection stations take charges of injecting the navigation messages and
commands to the GPS satellites, and receiving the telemetry information sent by the
satellites.
Since beginning to form the GPS constellation in 1978, as to April 2020, there
are a total of 74 GPS satellites with 7 types launched, including 11 Block I, 9 Block
II, 19 Block IIA, 13 Block IIR, 8 Block IIR-M, 12 Block IIF and 2 Block III. With
the GPS satellites’ modernizing, the optimized constellation operating and the User
Ranging Error (URE) decreasing, the performance of the GPS system is improved
gradually. In order to support the evolution of the platform and payload technologies
of GPS satellites, it is required to continuously improve the ground control network.
The development of ground control network for GPS constellation is divided into
the following four phases.
(1) From 1978 to 1985 was the demonstration phase. The ground closed-loop
control network was initially set up to support the on-orbit operation of GPS
Block I satellite series mainly through manual operation.
(2) From 1985 to 2007 was the full-constellation operation phase. The first generation of ground control segment with basic network architecture was built,
which has the capability to support the coordinated operation of 10 network
nodes to ensure the on-orbit operation of GPS Block II, IIA, IIR and IIR-M
satellite series.
(3) From 2007 to 2016 was the capability-improved phase. The second-generation
ground control segment with a network architecture facing users was built,
which can support more than 10 users of network nodes, to ensure the onorbit operation of the modernized GPS satellites, such as Block IIR-M and IIF
satellite series.
(4) From 2016 entered the new capability-upgraded phase. The Next-Generation
Operational Control System (OCX) will be built, with the network architecture
of central interface, modularization, flexibility and expandability, and the capability of supporting more than 100 network node users, to ensure the on-orbit
operation of current GPS satellites and transit to the TT&C tasks of the GPS
III satellites.
The GPS OCX will dramatically enhance GPS command, control and mission
capabilities and provide significant benefits to military and civilian users around the
world, and its development is following an incremental approach, with three versions
of Block-0, Block-1 and Block-2. The Block-0 is the launch and control system