China launches last BDS
satellite to complete global navigation constellation
June 23
China launched the last satellite
of the BeiDou Navigation Satellite System (BDS) on
Tuesday, marking the completion of the deployment of its
own global navigation system.
The satellite, the 55th in the
family of BeiDou that means "Big Dipper" in Chinese, was
launched at 9:43 a.m. (Beijing Time) and sent into the
preset orbit by a Long March-3B carrier rocket from the
Xichang Satellite Launch Center in southwest China's
Sichuan Province.
The mission, the 336th by the Long
March rocket series, was a "complete success," the
launch center said.
The satellite, designated to enter
the geostationary earth orbit (GEO), was the last one of
the BDS-3 system, which started to offer countries and
regions along the Belt and Road as well as the world
basic navigation service in December 2018.
BDS is one of four global
navigation satellite systems in the world. The other
three global navigation systems are GPS of the United
States, Galileo of the European Union, and GLONASS of
Russia.
China has been actively encouraging
the cooperation and exchanges between the BDS system and
other navigation systems in fields such as construction
and application, strengthening compatibility and
interoperability, resource sharing, and providing users
with more qualified, diversified, safe and reliable
services.
Compared with other global systems
in the world, the design of the BDS constellation is
unique, including medium earth orbit (MEO), inclined
geosynchronous orbit (IGSO) and GEO satellites.
The BDS-3 system consists of a
total of 30 satellites, including 24 MEO satellites,
three IGSO satellites and three GEO satellites.
The three GEO satellites, including
the newly launched one, can help significantly enhance
the overall technical indicators of the BDS-3 system,
according to the satellite developer China Academy of
Space Technology (CAST).
They feature two distinctive
creations of the BDS system -- active positioning and
short message communication, CAST said.
The short message communication
capability of the BDS-3 system has been improved 10
times. Users of the system can send a message of 1,200
Chinese characters at one time, as well as pictures, a
useful function in emergencies.
Active positioning, employing radio
measurement technology, can provide the locations of the
users, not only to themselves, but also to relevant
parties who are monitoring the users' whereabouts,
through the joint efforts of two GEO satellites.
The function is widely used in
search and rescue, fishing and other fields to help
guarantee people's safety.
The BDS system provides navigation
signals of multiple frequencies, and is able to improve
service accuracy by using combined multi-frequency
signals.
It also integrates navigation and
communication capabilities for the first time, and can
provide services of navigation, short message
communication, satellite-based augmentation,
international search and rescue, as well as precise
point positioning.
"BDS provides time-and-space
location benchmarks, which will have a great influence
on the country's social and economic development, as
well as people's lives," said Chen Zhonggui, chief
designer of the BDS-3 satellites at CAST.
"It will also lay the foundation
for new infrastructure construction, an important
direction for China's development in the next stage,"
Chen said.
China started to explore a
navigation satellite system suited to its national
conditions in the 1980s, laying down a three-step
strategy.
The BDS-1 project, the first step,
also known as BeiDou Navigation Satellite Demonstration
System, got official approval in 1994, when China was
still facing an international technology blockade and
domestic component manufacturers were not yet fully
fledged.
The team started the exploration
work with the solar arrays, recalled Fan Benyao, chief
designer of BDS-1 at CAST.
Insisting on self-reliance, the
older generation of the BDS team overcame a series of
technical problems, including those relating to the
Dongfanghong-3 satellite platform and key components
that might affect the service life of the satellites.
BDS-1 was completed and put into
operation in 2000 with the launching of two satellites,
providing useful experience in the areas of construction
and application, as well as training professionals for
the following projects.
The second step was to construct
the BDS-2 system, which started in 2004.
The team worked around the clock,
at one point conducting 200-hour non-stop power-on tests
at the launch site.
By the end of 2012, a total of 14
satellites, including five GEO satellites, five IGSO
satellites and four MEO satellites, were successfully
launched to complete the deployment.
The BDS-2 system is the world's
first hybrid constellation, in which satellites in three
kinds of orbits work in concert. It started providing
regional services for users in the Asia-Pacific region
in December 2012.
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