The Beidou Navigation System or
Beidou Satellite Navigation and Positioning System is a project by
ChinaThe People's Republic of China , commonly known as China, is the largest country in East Asia and the most populous in the world with over 1.3 billion people, approximately one-fifth of the world's population...
to develop an independent satellite navigation system. The current Beidou-1 system (made up of 4 satellites) is experimental and has limited coverage and application. However, China has planned to develop a truly global satellite navigation system consisting of 35 satellites (known as
CompassThe Compass system is a project by China to develop an independent global satellite navigation system.Compass is not an extension to the previously deployed Beidou-1, but a new GNSS system similar in principle to GPS and Galileo.-General:The new system will be a constellation of 35 satellites,...
or Beidou-2).
The Beidou Navigation System is named after the
Big DipperThe Plough or the Big Dipper is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial. The comprising stars are the seven brightest of the formal constellation Ursa Major.-Europe:...
constellationIn modern astronomy, a constellation is an area of the celestial sphere, defined by exact boundaries.The term "constellation" can also be used loosely to refer to just the more prominent visible stars that seem to form a pattern in that area.-Definitions:...
, which is known in Chinese as
Běidǒu.
The Beidou Navigation System or
Beidou Satellite Navigation and Positioning System is a project by
ChinaThe People's Republic of China , commonly known as China, is the largest country in East Asia and the most populous in the world with over 1.3 billion people, approximately one-fifth of the world's population...
to develop an independent satellite navigation system. The current Beidou-1 system (made up of 4 satellites) is experimental and has limited coverage and application. However, China has planned to develop a truly global satellite navigation system consisting of 35 satellites (known as
CompassThe Compass system is a project by China to develop an independent global satellite navigation system.Compass is not an extension to the previously deployed Beidou-1, but a new GNSS system similar in principle to GPS and Galileo.-General:The new system will be a constellation of 35 satellites,...
or Beidou-2).
Name
The Beidou Navigation System is named after the
Big DipperThe Plough or the Big Dipper is an asterism of seven stars that has been recognized as a distinct grouping in many cultures from time immemorial. The comprising stars are the seven brightest of the formal constellation Ursa Major.-Europe:...
constellationIn modern astronomy, a constellation is an area of the celestial sphere, defined by exact boundaries.The term "constellation" can also be used loosely to refer to just the more prominent visible stars that seem to form a pattern in that area.-Definitions:...
, which is known in Chinese as
Běidǒu. The name literally means "Northern Dipper", the name given by Chinese astronomers to the seven brightest stars of Ursa Major or 'the Great Bear' constellation.
Historically, this set of stars was used in navigation to locate the
North StarThe North Star is the prominent pole star that lies closest in the sky to the north celestial pole and which appears directly overhead to an observer at the Earth's North Pole. Currently, this is Polaris, which lies about two thirds of a degree from the north celestial pole, at the end of the...
PolarisPolaris is the brightest star in the constellation Ursa Minor. It is very close to the north celestial pole , making it the current northern pole star.Polaris is about 430 light-years from Earth...
. As such, Beidou also serves as a metaphor for the purpose of the satellite navigation system.
History
Beidou 1A was launched on 30 October 2000, Beidou 1B followed on 20 December 2000, Beidou 1C was put into orbit on 25 May 2003, Beidou-1D in February 2007, Compass-M1 (to validate frequencies for the Beidou-2 constellation) in April 2009. The second Beidou-2 constellation satellite (Compass-G2) was launched on 15 April 2009
.
In September 2003, China intended to join the
Galileo positioning systemGalileo is a global navigation satellite system currently being built by the European Union and European Space Agency . The €3.4 billion project is an alternative and complementary to the U.S. Global Positioning System and the Russian GLONASS...
project. China was to invest
€The euro is the official currency of 16 of the 27 Member States of the European Union . The states, known collectively as the Eurozone, are Austria, Belgium, Cyprus, Finland, France, Germany, Greece, Ireland, Italy, Luxembourg, Malta, the Netherlands, Portugal, Slovakia, Slovenia and Spain...
230 million (
USDThe United States dollar is the unit of currency of the United States. The U.S. dollar is normally abbreviated as the dollar sign, $, or as USD or US$ to distinguish it from other dollar-denominated currencies and from others that use the $ symbol. It is divided into 100 cents .The U.S...
296 million,
GBPThe pound sterling , often simply called the pound, is the currency of the United Kingdom, its Crown dependencies and the British Overseas Territories of South Georgia and the South Sandwich Islands and British Antarctic Territory...
160 million) in Galileo over the next few years.
(Galileo is not yet operational, although two experimental satellites have been launched.)
. China has since abandoned its relationship with Galileo.
On November 2, 2006, China announced that from 2008 Beidou would offer an open service with an accuracy of 10 meters.
In 2007, the official
Xinhua News Agency reported that the resolution of the Beidou system was as high as 0.5 metres, considerably better than unaided GPS. The receivers are described
here.
Satellites
(as of August 2009)
| Date | Launcher | Satellite | Orbit | In Use |
|---|
| 10/31/2000 |
LM-3A A Long March rocket is any rocket in a family of expendable launch systems operated by the People's Republic of China. Development and design falls under the auspices of the China Academy of Launch Vehicle Technology. In English, the rockets are abbreviated as LM- for export and CZ- within China...
|
Beidou-1A |
GEO A geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero...
140°E |
No |
| 12/21/2000 |
LM-3A |
Beidou-1B |
GEO 80°E |
(unclear) |
| 5/25/2003 |
LM-3A |
Beidou-1C |
GEO 110.5°E |
Yes |
| 2/3/2007 |
LM-3A |
Beidou-1D |
deorbited |
No |
| 4/14/2007 |
LM-3A |
Compass-M1 |
MEOMedium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....
21,500 km |
Yes |
| 4/15/2009 |
LM-3C |
Compass-G2 |
GEO~80°E |
No |
- Note: all dates are based on China Standard Time
Current technology (Beidou-1)
Unlike the GPS,
GLONASSGLONASS is a radio-based satellite navigation system, developed by the former Soviet Union and now operated for the Russian government by the Russian Space Forces.It is an alternative and complementary to the United States' Global Positioning System , the Chinese Compass...
, and
GalileoGalileo is a global navigation satellite system currently being built by the European Union and European Space Agency . The €3.4 billion project is an alternative and complementary to the U.S. Global Positioning System and the Russian GLONASS...
systems, which use
medium Earth orbitMedium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....
satellites, Beidou 1 uses satellites in
geostationary orbitA geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero...
. This means that the system does not require a large constellation of satellites, but it also limits the coverage to areas on Earth where the satellites are visible. The area that can be serviced is from 70°E to 140°E, and from 5°N to 55°N.
The Beidou satellites themselves were based on the Chinese
DFH-3China is also eager to provide its Dong Fang Hong technology as the basis for satellites designed, manufactured and launched by China for international customers, as it did for Nigeria with the NigComSat-1 whose lifespan was cut short due to communications and power problems.- Satellites launched...
geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
To calculate a position, the following procedure is used:
- A signal is transmitted skyward by a remote terminal.
- Each of the geostationary satellites receive the signal.
- Each satellite sends the accurate time of when each received the signal to a ground station.
- The ground station calculates the longitude and latitude of the remote terminal, and determines the altitude from a relief map.
- The ground station sends the remote terminal's 3D position to the satellites.
- The satellites broadcast the calculated position to the remote terminal.
Additionally, the terminal can communicate with the ground station by sending and receiving short messages.
Future Plans (Beidou-2 or Compass)
The four satellites (1A,1B,1C and 1D) mentioned above were designed as experimental satellites.
The new system will be a constellation of 35 satellites, which include 5
geostationary orbitA geostationary orbit is a geosynchronous orbit directly above the Earth's equator , with a period equal to the Earth's rotational period and an orbital eccentricity of approximately zero...
(GEO) satellites, for backward compatibility with Beidou-1, and 30
medium Earth orbitMedium Earth orbit , sometimes called intermediate circular orbit , is the region of space around the Earth above low Earth orbit and below geostationary orbit ....
(MEO) satellites, that will offer complete coverage of the globe. There will be two levels of service provided; free service for those in China, and licensed service for the military.
- The free service will have a 10 meter location-tracking accuracy, will synchronize clocks with an accuracy of 50 ns, and measure speeds within 0.2 m/s.
- The licensed service will be more accurate than the free service, can be used for communication, and will supply information about the system status to the users.
Two satellites for Beidou 2 have been launched in early 2007 and in early 2009. In the next few years, China plans to continue setting up the system for global operation from 2015.
External links