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4 Navigations from Ground to Space
etc. The user segment consists of various types of BDS-1 user terminals, such as
handheld terminal, vehicle-onboard terminal, ship-onboard terminal and command
terminal, which are used to submit the positioning application to the control center,
correct time, receive location data, short message, etc. The active navigation mechanism with two-way timing and ranging is used in the BeiDou test system, which
can provide location determination, one-way or two-way time service, short-message
communication and other services for medium and low dynamic users and static users
within China and its surrounding areas, with the positioning accuracy of 20 m, the
timing accuracy of 100 ns for one way and 20 ns for two way, and the number of single
short-message communication words of 20 Chinese characters. The BeiDou test
system has played an important role in promoting Chinese economic construction,
social development and national security.
The second phase is from 2004 to 2012, to build the BeiDou navigation satellite
system for regional service. In 2004, the Chinese government launched the project of
building the BeiDou navigation satellite system, known as BDS-2. In April 2007, the
first BDS-2 satellite was launched successfully, and as of October 2012, a total of 16
BDS-2 satellites had been sent into the orbits, forming the BDS-2 constellation with
five GEO satellites, five Inclination Geo-Synchronization Orbit (IGSO) satellites and
four Medium Earth Orbit (MEO) satellites. The five GEO satellites were located at
58.75°E, 80°E, 110.5°E, 140°E and 160°E over the equator. The five IGSO satellites
were with an orbital altitude of 35,786 km and an inclination of 55° to the equatorial
plane, where the three satellite sub-point tracks were coincident, with the equatorial
intersection at 118°E, and the other two satellites sub-point tracks were coincident,
with the equatorial intersection at 95°E. By using the constellation Walker 24/3/1,
two of the four MEO satellites were put into the first orbital plane and the other two
into the second orbital plane. The MEO satellites were with the orbital altitude of
21,528 km, the inclination 55° to the equatorial plane and the repeated period of 13
circles per 7 days. Moreover, the ground segment of the BDS-2 is composed of monitoring stations, master control stations, time synchronization and injection stations,
which are used for the BDS-2 satellites tracking and monitoring, data processing,
task planning, operation management, navigation message preparation, navigation
message injected to the satellites, etc. The user segment consists of various types of
BDS-2 user terminal equipment. The passive navigation mechanism with one-way
timing and ranging is used in the BDS-2 system. In 2012, the BDS-2 system had
the capability of affording regional continuous navigation, positioning and timing
service, with the service area ranges from 55°S to 55°N and from 70°E to 150°E, and
the horizontal and vertical positioning accuracies are better than 10 m (2-sigma).
The third phase is from 2013 to 2020, to build the BeiDou navigation satellite
system for global service. After the BDS regional system built in 2012, the construction of the BDS project in the third phase was pushed forward continuously to
achieve the global coverage of the BDS signals, which is also known as BDS-3.
By inheriting the technical schemes of both active and passive services, the BDS3 system can provide the positioning, navigation and timing, global short-message
communication, and international search and rescue services for global users. Meanwhile, for regional users within China and its surrounding areas, it can also offer the
4 Navigations from Ground to Space
etc. The user segment consists of various types of BDS-1 user terminals, such as
handheld terminal, vehicle-onboard terminal, ship-onboard terminal and command
terminal, which are used to submit the positioning application to the control center,
correct time, receive location data, short message, etc. The active navigation mechanism with two-way timing and ranging is used in the BeiDou test system, which
can provide location determination, one-way or two-way time service, short-message
communication and other services for medium and low dynamic users and static users
within China and its surrounding areas, with the positioning accuracy of 20 m, the
timing accuracy of 100 ns for one way and 20 ns for two way, and the number of single
short-message communication words of 20 Chinese characters. The BeiDou test
system has played an important role in promoting Chinese economic construction,
social development and national security.
The second phase is from 2004 to 2012, to build the BeiDou navigation satellite
system for regional service. In 2004, the Chinese government launched the project of
building the BeiDou navigation satellite system, known as BDS-2. In April 2007, the
first BDS-2 satellite was launched successfully, and as of October 2012, a total of 16
BDS-2 satellites had been sent into the orbits, forming the BDS-2 constellation with
five GEO satellites, five Inclination Geo-Synchronization Orbit (IGSO) satellites and
four Medium Earth Orbit (MEO) satellites. The five GEO satellites were located at
58.75°E, 80°E, 110.5°E, 140°E and 160°E over the equator. The five IGSO satellites
were with an orbital altitude of 35,786 km and an inclination of 55° to the equatorial
plane, where the three satellite sub-point tracks were coincident, with the equatorial
intersection at 118°E, and the other two satellites sub-point tracks were coincident,
with the equatorial intersection at 95°E. By using the constellation Walker 24/3/1,
two of the four MEO satellites were put into the first orbital plane and the other two
into the second orbital plane. The MEO satellites were with the orbital altitude of
21,528 km, the inclination 55° to the equatorial plane and the repeated period of 13
circles per 7 days. Moreover, the ground segment of the BDS-2 is composed of monitoring stations, master control stations, time synchronization and injection stations,
which are used for the BDS-2 satellites tracking and monitoring, data processing,
task planning, operation management, navigation message preparation, navigation
message injected to the satellites, etc. The user segment consists of various types of
BDS-2 user terminal equipment. The passive navigation mechanism with one-way
timing and ranging is used in the BDS-2 system. In 2012, the BDS-2 system had
the capability of affording regional continuous navigation, positioning and timing
service, with the service area ranges from 55°S to 55°N and from 70°E to 150°E, and
the horizontal and vertical positioning accuracies are better than 10 m (2-sigma).
The third phase is from 2013 to 2020, to build the BeiDou navigation satellite
system for global service. After the BDS regional system built in 2012, the construction of the BDS project in the third phase was pushed forward continuously to
achieve the global coverage of the BDS signals, which is also known as BDS-3.
By inheriting the technical schemes of both active and passive services, the BDS3 system can provide the positioning, navigation and timing, global short-message
communication, and international search and rescue services for global users. Meanwhile, for regional users within China and its surrounding areas, it can also offer the