The BeiDou Navigation Satellite System (BDS; ) is a Chinese
satellite navigation
A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pr ...
system. It consists of two separate
satellite constellation
A satellite constellation is a group of artificial satellites working together as a system. Unlike a single satellite, a constellation can provide permanent global or near-global coverage, such that at any time everywhere on Earth at least one sa ...
s. The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System and also known as BeiDou-1, consisted of three satellites which, beginning in 2000, offered limited coverage and navigation services, mainly for users in China and neighboring regions. BeiDou-1 was decommissioned at the end of 2012.
The second generation of the system, officially called the BeiDou Navigation Satellite System (BDS) and also known as COMPASS or BeiDou-2, became operational in China in December 2011 with a partial constellation of 10 satellites in orbit.
Since December 2012, it has been offering services to customers in the
Asia-Pacific
Asia-Pacific (APAC) is the part of the world near the western Pacific Ocean. The Asia-Pacific region varies in area depending on context, but it generally includes East Asia, Russian Far East, South Asia, Southeast Asia, Australia and Pacific Isla ...
region.
In 2015, China launched the third generation BeiDou system (BeiDou-3) for global coverage. The first BDS-3 satellite was launched on 30 March 2015.
On 27 December 2018, BeiDou Navigation Satellite System started providing global services. The 35th and the final satellite of BDS-3 was launched into orbit on 23 June 2020. It was said in 2016 that BeiDou-3 will reach millimeter-level accuracy (with post-processing).
On 23 June 2020, the last BeiDou satellite was successfully launched, the launch of the 55th satellite in the Beidou family. The third iteration of the Beidou Navigation Satellite System provides full global coverage for timing and navigation, offering an alternative to Russia's
GLONASS
GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
, the European
Galileo positioning system
Galileo is a global navigation satellite system (GNSS) that went live in 2016, created by the European Union through the European Space Agency (ESA), operated by the European Union Agency for the Space Programme (EUSPA), headquartered in Pr ...
, and the US's
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
.
According to ''
China Daily
''China Daily'' () is an English-language daily newspaper owned by the Central Propaganda Department of the Chinese Communist Party.
Overview
''China Daily'' has the widest print circulation of any English-language newspaper in China. T ...
'', in 2015, fifteen years after the satellite system was launched, it was generating a turnover of $31.5 billion per annum for major companies such as
China Aerospace Science and Industry Corporation
The China Aerospace Science & Industry Corporation Limited (CASIC) is a Chinese state-owned enterprise that designs, develops and manufactures a range of spacecraft, launch vehicles, strategic and tactical missile systems, and ground equipment ...
,
AutoNavi Holdings Ltd., and
China North Industries Group Corp. The industry has grown an average of over 20% in value annually to reach $64 billion in 2020 according to
Xinhua
Xinhua News Agency (English pronunciation: )J. C. Wells: Longman Pronunciation Dictionary, 3rd ed., for both British and American English, or New China News Agency, is the official state news agency of the People's Republic of China. Xinhua ...
citing data.
Domestic industry reports forecast the satellite navigation service market output value, directly generated and driven by the Beidou system, will be worth 1 trillion yuan ($156.22 billion) by 2025, and $467 billion by 2035.
Nomenclature
The official English name of the system is ''BeiDou Navigation Satellite System''. It is named after the
Big Dipper
The Big Dipper ( US, Canada) or the Plough ( UK, Ireland) is a large asterism consisting of seven bright stars of the constellation Ursa Major; six of them are of second magnitude and one, Megrez (δ), of third magnitude. Four define a "bowl" ...
asterism, which is known in Chinese as (). The name literally means "Northern Dipper", the name given by ancient Chinese astronomers to the seven brightest stars of the
Ursa Major constellation
Ursa is a Latin word meaning bear. Derivatives of this word are ursine or Ursini.
Ursa may also refer to:
General
* URSA Extracts (United States of America), a California cannabis concentrate company
* Ursa (Finland), a Finnish astronomical a ...
.
Historically, this set of stars was used in navigation to locate the
North Star
Polaris is a star in the northern circumpolar constellation of Ursa Minor. It is designated α Ursae Minoris ( Latinized to ''Alpha Ursae Minoris'') and is commonly called the North Star or Pole Star. With an apparent magnitude that ...
. As such, the name BeiDou also serves as a metaphor for the purpose of the satellite navigation system.
History
Conception and initial development
The original idea of a Chinese satellite navigation system was conceived by
Chen Fangyun
Chen Fangyun (; 3 April 1916 – 29 April 2000) was a Chinese electrical engineer. Considered the founder of radio electronics in China, he was pivotal in the development of telemetry, tracking and command (TT&C) systems that control China's satel ...
and his colleagues in the 1980s.
The risk of denied access to GPS during the
Yinhe incident
The ''Yinhe'' incident () occurred after a claim was made in 1993 by the United States government that the China-based container ship ''Yinhe'' () was carrying chemical weapon materials to Iran. The United States Navy forced the surrounding Middle ...
in 1993 and including an alleged case in 1996 during the
Third Taiwan Strait Crisis
The Third Taiwan Strait Crisis, also called the 1995–1996 Taiwan Strait Crisis or the 1996 Taiwan Strait Crisis, was the effect of a series of missile tests conducted by the People's Republic of China (PRC) in the waters surrounding Taiwan ...
, gave impetus to the creation of BeiDou which officially began in 1994.
According to the
China National Space Administration
China National Space Administration (CNSA; ) is the government agency of the People's Republic of China that is responsible for civil space administration and international space cooperation, including organizing or leading foreign exchanges ...
, in 2010, the development of the system would be carried out in three steps:
# 2000–2003: experimental BeiDou navigation system consisting of three satellites
# By 2012: regional BeiDou navigation system covering China and neighboring regions
# By 2020: global BeiDou navigation system
The first satellite, ''BeiDou-1A'', was launched on 30 October 2000, followed by ''BeiDou-1B'' on 20 December 2000. The third satellite, ''BeiDou-1C'' (a backup satellite), was put into orbit on 25 May 2003.
The successful launch of ''BeiDou-1C'' also meant the establishment of the BeiDou-1 navigation system.
On 2 November 2006, China announced that from 2008 BeiDou would offer an open service with an accuracy of 10 metres, timing of 0.2 microseconds, and speed of 0.2 metres/second.
In February 2007, the fourth and last satellite of the BeiDou-1 system, ''BeiDou-1D'' (sometimes called ''BeiDou-2A'', serving as a backup satellite), was launched.
It was reported that the satellite had suffered from a control system malfunction but was then fully restored.
In April 2007, the first satellite of BeiDou-2, namely ''Compass-M1'' (to validate frequencies for the BeiDou-2 constellation) was successfully put into its working orbit. The second BeiDou-2 constellation satellite ''Compass-G2'' was launched on 15 April 2009.
On 15 January 2010, the official website of the BeiDou Navigation Satellite System went online,
and the system's third satellite (''Compass-G1'') was carried into its orbit by a
Long March 3C
The Long March 3C (), also known as the Changzheng 3C, CZ-3C and LM-3C, is a Chinese orbital launch vehicle. It is launched from Launch Complex 2 and 3 at the Xichang Satellite Launch Center (XSLC). A three-stage rocket with two strapon liquid ...
rocket on 17 January 2010.
On 2 June 2010, the fourth satellite was launched successfully into orbit.
The fifth orbiter was launched into space from
Xichang Satellite Launch Center
The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan.
The facility beca ...
by an
LM-3I carrier rocket on 1 August 2010.
Three months later, on 1 November 2010, the sixth satellite was sent into orbit by LM-3C.
Another satellite, the Beidou-2/Compass IGSO-5 (fifth inclined geosynchronous orbit) satellite, was launched from the Xichang Satellite Launch Center by a
Long March 3A
The Long March 3A (), also known as the Chang Zheng 3A, CZ-3A and LM-3A, is a Chinese orbital carrier rocket design. It is a 3-stage rocket, and is usually used to place communications satellites and Beidou navigation satellites into geosynchron ...
on 1 December 2011 (UTC).
Chinese involvement in Galileo system
In September 2003, China intended to join the European
Galileo positioning system
Galileo is a global navigation satellite system (GNSS) that went live in 2016, created by the European Union through the European Space Agency (ESA), operated by the European Union Agency for the Space Programme (EUSPA), headquartered in Pr ...
project and was to invest €230 million (US$296 million, £160 million) in Galileo over the next few years. At the time, it was believed that China's "BeiDou" navigation system would then only be used by its armed forces.
In October 2004, China officially joined the Galileo project by signing the ''Agreement on the Cooperation in the Galileo Program between the "Galileo Joint Undertaking" (GJU) and the "National Remote Sensing Centre of China" (NRSCC)''. Based on the Sino-European Cooperation Agreement on Galileo program, China Galileo Industries (CGI), the prime contractor of the China's involvement in Galileo programs, was founded in December 2004. By April 2006, eleven cooperation projects within the Galileo framework had been signed between China and EU.
However, the Hong Kong-based ''
South China Morning Post
The ''South China Morning Post'' (''SCMP''), with its Sunday edition, the ''Sunday Morning Post'', is a Hong Kong-based English-language newspaper owned by Alibaba Group. Founded in 1903 by Tse Tsan-tai and Alfred Cunningham, it has remained ...
'' reported in January 2008 that China was not satisfied with its role in the Galileo project and was to compete with Galileo in the Asian market.
Phase III
* In November 2014, Beidou became part of the World-Wide Radionavigation System (WWRNS) at the 94th meeting of the
International Maritime Organization
The International Maritime Organization (IMO, French: ''Organisation maritime internationale'') is a specialised agency of the United Nations responsible for regulating shipping. The IMO was established following agreement at a UN conference ...
(IMO) Maritime Safety Committee, which approved the "Navigation Safety Circular" of the BeiDou Navigation Satellite System (BDS).
* At Beijing time 21:52, 30 March 2015, the first new-generation BeiDou Navigation satellite (and the 17th overall) was successfully set to orbit by a
Long March 3C
The Long March 3C (), also known as the Changzheng 3C, CZ-3C and LM-3C, is a Chinese orbital launch vehicle. It is launched from Launch Complex 2 and 3 at the Xichang Satellite Launch Center (XSLC). A three-stage rocket with two strapon liquid ...
rocket.
* On 20 April 2019, a BeiDou satellite was successfully launched. Launch occurred at 22:41
Beijing time
The time in China follows a single standard time offset of UTC+08:00 (eight hours ahead of Coordinated Universal Time), even though the country spans almost five geographical time zones. The official national standard time is called ''Beijing Tim ...
, and the Long March 3B delivered the BeiDou navigation payload into an elliptical transfer orbit ranging between 220 kilometres and 35,787 kilometres, with an inclination of 28.5° to the equator, according to U.S. military tracking data.
* On 23 June 2020, the final BeiDou satellite was successfully launched, the launch of the 55th satellite in the Beidou family. The third iteration of the Beidou Navigation Satellite System provides global coverage for timing and navigation, offering an alternative to Russia's
GLONASS
GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
and the European
Galileo positioning system
Galileo is a global navigation satellite system (GNSS) that went live in 2016, created by the European Union through the European Space Agency (ESA), operated by the European Union Agency for the Space Programme (EUSPA), headquartered in Pr ...
, as well as the US's
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
.
BeiDou-1
Description
BeiDou-1 was an experimental regional navigation system, which consisted of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese
DFH-3
Dongfanghong () was a satellite program of the People's Republic of China. The program started in August 1965 as Project 651—a less ambitious successor to the earlier Project 581—with the goal of launching a satellite heavier than both Sputn ...
geostationary communications satellite and had a launch weight of 1000 kg each.
Unlike the American
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
, Russian
GLONASS
GLONASS (russian: ГЛОНАСС, label=none, ; rus, links=no, Глобальная навигационная спутниковая система, r=Global'naya Navigatsionnaya Sputnikovaya Sistema, t=Global Navigation Satellite System) is ...
, and European
Galileo
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
systems, which use
medium Earth orbit
A medium Earth orbit (MEO) is an geocentric orbit, Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between above sea level. satellites, BeiDou-1 used satellites in
geostationary orbit
A geostationary orbit, also referred to as a geosynchronous equatorial orbit''Geostationary orbit'' and ''Geosynchronous (equatorial) orbit'' are used somewhat interchangeably in sources. (GEO), is a circular geosynchronous orbit in altitud ...
. 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 longitude 70° E to 140° E and from latitude 5° N to 55° N. A frequency of the system is 2491.75 MHz.
Completion
The first satellite, BeiDou-1A, was launched on 31 October 2000. The second satellite, BeiDou-1B, was successfully launched on 21 December 2000. The last operational satellite of the constellation, BeiDou-1C, was launched on 25 May 2003.
Position calculation
In 2007, the official
Xinhua News Agency
Xinhua News Agency (English pronunciation: )J. C. Wells: Longman Pronunciation Dictionary, 3rd ed., for both British and American English, or New China News Agency, is the official state news agency of the People's Republic of China. Xinhua ...
reported that the resolution of the BeiDou system was as low as 0.5 metre. With the existing user terminals it appears that the calibrated accuracy is 20 m (100 m, uncalibrated).
Terminals
In 2008, a BeiDou-1 ground terminal cost around (), almost 10 times the price of a contemporary GPS terminal. The price of the terminals was explained as being due to the cost of imported microchips. At the China High-Tech Fair ELEXCON of November 2009 in
Shenzhen
Shenzhen (; ; ; ), also historically known as Sham Chun, is a major sub-provincial city and one of the special economic zones of China. The city is located on the east bank of the Pearl River estuary on the central coast of southern province ...
, a BeiDou terminal priced at was presented.
Applications
* Over 1000 BeiDou-1 terminals were used after the
2008 Sichuan earthquake, providing information from the disaster area.
* As of October 2009, all Chinese border guards in
Yunnan
Yunnan , () is a landlocked Provinces of China, province in Southwest China, the southwest of the People's Republic of China. The province spans approximately and has a population of 48.3 million (as of 2018). The capital of the province is ...
were equipped with BeiDou-1 devices.
Sun Jiadong
Sun Jiadong (; born 8 April 1929) is a Chinese aerospace engineer who is an expert in carrier rocket and satellite technology. He has long served as a leader of Chinese satellite projects, and is currently the chief designer for the Chinese Lunar ...
, the chief designer of the navigation system, said in 2010 that "Many organizations have been using our system for a while, and they like it very much".
Decommissioning
BeiDou-1 was decommissioned at the end of 2012, after the BeiDou-2 system became operational.
BeiDou-2
Description
![Beidou Navigation Satellite System 2012](https://upload.wikimedia.org/wikipedia/commons/3/33/Beidou_Navigation_Satellite_System_2012.png)
BeiDou-2 (formerly known as COMPASS) is not an extension to the older BeiDou-1, but rather supersedes it outright. The new system is a constellation of 35 satellites, which include 5 geostationary orbit satellites for backward compatibility with BeiDou-1, and 30 non-geostationary satellites (27 in
medium Earth orbit
A medium Earth orbit (MEO) is an geocentric orbit, Earth-centered orbit with an altitude above a low Earth orbit (LEO) and below a high Earth orbit (HEO) – between above sea level. and 3 in inclined
geosynchronous orbit
A geosynchronous orbit (sometimes abbreviated GSO) is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds (one sidereal day). The synchronization of rotation and orbital ...
),
that offer complete coverage of the globe.
The ranging signals are based on the
CDMA
Code-division multiple access (CDMA) is a channel access method used by various radio communication technologies. CDMA is an example of multiple access, where several transmitters can send information simultaneously over a single communication ...
principle and have complex structure typical of
Galileo
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642) was an Italian astronomer, physicist and engineer, sometimes described as a polymath. Commonly referred to as Galileo, his name was pronounced (, ). He was ...
or modernized
GPS
The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
. Similar to the other
global navigation satellite systems
A satellite navigation or satnav system is a system that uses satellites to provide autonomous geo-spatial positioning. It allows satellite navigation devices to determine their location (longitude, latitude, and altitude/elevation) to high pre ...
(GNSSs), there are two levels of positioning service: open (public) and restricted (military). The public service is available globally to general users. When all the currently planned GNSSs are deployed, users of multi-constellation receivers will benefit from a total over 100 satellites, which will significantly improve all aspects of positioning, especially availability of the signals in so-called
urban canyons
An urban canyon (also known as a street canyon) is a place where the street is flanked by buildings on both sides creating a canyon-like environment, evolved etymologically from the Canyon of Heroes in Manhattan. Such human-built canyons are made ...
. The general designer of the COMPASS navigation system is
Sun Jiadong
Sun Jiadong (; born 8 April 1929) is a Chinese aerospace engineer who is an expert in carrier rocket and satellite technology. He has long served as a leader of Chinese satellite projects, and is currently the chief designer for the Chinese Lunar ...
, who is also the general designer of its predecessor, the original BeiDou navigation system. All BeiDou satellites are equipped with laser
retroreflector
A retroreflector (sometimes called a retroflector or cataphote) is a device or surface that reflects radiation (usually light) back to its source with minimum scattering. This works at a wide range of angle of incidence, unlike a planar mirror, ...
arrays for
satellite laser ranging
In satellite laser ranging (SLR) a global network of observation stations measures the round trip time of flight of ultrashort pulses of light to satellites equipped with retroreflectors. This provides instantaneous range measurements of milli ...
and the verification of the orbit quality.
Accuracy
There are two levels of service provided – a free service to civilians and licensed service to the
Chinese government
The Government of the People's Republic of China () is an authoritarian political system in the People's Republic of China under the exclusive political leadership of the Chinese Communist Party (CCP). It consists of legislative, executive, mili ...
and military.
The free civilian service has a 10-metre location-tracking accuracy, synchronizes clocks with an accuracy of 10 nanoseconds, and measures speeds to within 0.2 m/s. The restricted military service has a location accuracy of 10 centimetre, can be used for communication, and will supply information about the system status to the user. In 2019, the International GNSS Service started providing precise orbits of BeiDou satellites in experimental products.
To date, the military service has been granted only to the
People's Liberation Army
The People's Liberation Army (PLA) is the principal military force of the People's Republic of China and the armed wing of the Chinese Communist Party (CCP). The PLA consists of five service branches: the Ground Force, Navy, Air Force, ...
and to the
Pakistan Armed Forces
The Pakistan Armed Forces (; ) are the military forces of Pakistan. It is the world's sixth-largest military measured by active military personnel and consist of three formally uniformed services—the Army, Navy, and the Air Force, which are ...
.
Frequencies
Frequencies for COMPASS are allocated in four bands: E1, E2, E5B, and E6; they overlap with Galileo. The fact of overlapping could be convenient from the point of view of the receiver design, but on the other hand raises the issues of system interference, especially within E1 and E2 bands, which are allocated for Galileo's publicly regulated service. However, under
International Telecommunication Union
The International Telecommunication Union is a specialized agency of the United Nations responsible for many matters related to information and communication technologies. It was established on 17 May 1865 as the International Telegraph Unio ...
(ITU) policies, the first nation to start broadcasting in a specific frequency will have priority to that frequency, and any subsequent users will be required to obtain permission prior to using that frequency, and otherwise ensure that their broadcasts do not interfere with the original nation's broadcasts. As of 2009, it appeared that Chinese COMPASS satellites would start transmitting in the E1, E2, E5B, and E6 bands before Europe's Galileo satellites and thus have primary rights to these frequency ranges.
Although little was officially announced by Chinese authorities about the signals of the new system, the launch of the first COMPASS satellite permitted independent researchers not only to study general characteristics of the signals, but even to build a COMPASS receiver.
Compass-M1
Compass-M1 is an experimental satellite launched for signal testing and validation and for the frequency filing on 14 April 2007. The role of Compass-M1 for Compass is similar to the role of the
GIOVE
GIOVE (; ), or Galileo In-Orbit Validation Element, is the name for two satellites built for the European Space Agency (ESA) to test technology in orbit for the Galileo positioning system.
The name was chosen as a tribute to Galileo Galilei, who ...
satellites for the Galileo system. The orbit of Compass-M1 is nearly circular, has an altitude of 21,150 km and an inclination of 55.5°.
Compass-M1 transmits in 3 bands: E2, E5B, and E6. In each frequency band two coherent sub-signals have been detected with a phase shift of 90° (in
quadrature). These signal components are further referred to as "I" and "Q". The "I" components have shorter codes and are likely to be intended for the open service. The "Q" components have much longer codes, are more interference resistive, and are probably intended for the restricted service.
The investigation of the transmitted signals started immediately after the launch of Compass-M1 on 14 April 2007. Soon after in June 2007, engineers at
CNES
The (CNES; French: ''Centre national d'études spatiales'') is the French government space agency (administratively, a "public administration with industrial and commercial purpose"). Its headquarters are located in central Paris and it is und ...
reported the spectrum and structure of the signals. A month later, researchers from
Stanford University
Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...
reported the complete decoding of the "I" signals components. The knowledge of the codes allowed a group of engineers at
Septentrio
Septentrio N.V. is a designer and manufacturer of high-end multi-frequency GNSS receivers. Its main target is to provide GNSS receiver boards and modules for further system integration by Original Equipment Manufacturers (OEMs). Septentrio's core ...
to build the COMPASS receiver and report tracking and multipath characteristics of the "I" signals on E2 and E5B.
Operation
![Ground track beidou-m2 satellite](https://upload.wikimedia.org/wikipedia/commons/3/39/Ground_track_beidou-m2_satellite.jpg)
In December 2011, the system went into operation on a trial basis.
It started providing navigation, positioning and timing data to China and the neighbouring area for free from 27 December 2011. During this trial run, Compass offered positioning accuracy to within 25 metre and the precision improved as more satellites were launched. Upon the system's official launch, it pledged to offer general users positioning information accurate to the nearest 10 m, measure speeds within 0.2 metre per second, and provide signals for clock synchronisation accurate to 0.02 microseconds.
The BeiDou-2 system began offering services for the Asia-Pacific region in December 2012.
[ At this time, the system could provide positioning data between longitude 55° E to 180° E and from latitude 55° S to 55° N.
The new-generation BeiDou satellites support short message service.]
Completion
In December 2011, Xinhua
Xinhua News Agency (English pronunciation: )J. C. Wells: Longman Pronunciation Dictionary, 3rd ed., for both British and American English, or New China News Agency, is the official state news agency of the People's Republic of China. Xinhua ...
stated that " e basic structure of the BeiDou system has now been established, and engineers are now conducting comprehensive system test and evaluation. The system will provide test-run services of positioning, navigation and time for China and the neighboring areas before the end of this year, according to the authorities". The system became operational in the China region that same month. The global navigation system should be finished by 2020.
As of December 2012, 16 satellites for BeiDou-2 had been launched, with 14 in service. And as of December 2017, 150 m Chinese smartphones (20% of the market) were equipped to utilize Beidou.
BeiDou-3
The third phase of the BeiDou system (BDS-3) includes three GEO satellites, three IGSO satellites, and twenty-four MEO satellites which introduce new signal frequencies B1C/B1I/B1A (1575.42MHz), B2a/B2b (1191.795MHz), B3I/B3Q/B3A (1268.52MHz), and Bs test frequency (2492.028MHz). Interface control documents on the new open signals were published in 2017–2018.[Update on the BeiDou Satellite Navigation System](_blank)
. 12th ICG Meeting. Jia-Qing Ma, China Satellite Navigation Office.
On 23 June 2020, the BDS-3 constellation deployment was fully completed after the last satellite was successfully launched at the Xichang Satellite Launch Center
The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan.
The facility beca ...
. BDS-3 satellites also include SBAS (B1C, B2a, B1A) and search and rescue transponder capabilities.
Characteristics of the "I" signals on E2 and E5B are generally similar to the civilian codes of GPS (L1-CA and L2C), but Compass signals have somewhat greater power. The notation of Compass signals used in this page follows the naming of the frequency bands and agrees with the notation used in the American literature on the subject, but the notation used by the Chinese seems to be different.
There has also been an experimental S band
The S band is a designation by the Institute of Electrical and Electronics Engineers (IEEE) for a part of the microwave band of the electromagnetic spectrum covering frequencies from 2 to 4 gigahertz (GHz). Thus it crosses the convention ...
broadcast called "Bs" at 2492.028 MHz, following similar experiments on Beidou-1.
Constellation
The regional BeiDou-1 system was decommissioned at the end of 2012.
The first satellite of the second-generation system, Compass-M1 was launched in 2007. It was followed by further nine satellites during 2009–2011, achieving functional regional coverage. A total of 16 satellites were launched during this phase.
In 2015, the system began its transition towards global coverage with the first launch of a new-generation of satellites, and the 17th one within the new system. On 25 July 2015, the 18th and 19th satellites were successfully launched from the Xichang Satellite Launch Center
The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan.
The facility beca ...
, marking the first time for China to launch two satellites at once on top of a Long March 3B
The Long March 3B (, ''Chang Zheng 3B''), also known as the CZ-3B and LM-3B, is a Chinese orbital launch vehicle. Introduced in 1996, it is launched from Launch Area 2 and 3 at the Xichang Satellite Launch Center in Sichuan. A three-stage rocke ...
/Expedition 1
Expedition 1 was the first long-duration stay on the International Space Station (ISS). The three-person crew stayed aboard the station for 136 days, from November 2000 to March 2001. It was the beginning of an uninterrupted human presence on the ...
carrier rocket
A launch vehicle or carrier rocket is a rocket designed to carry a payload (spacecraft or satellites) from the Earth's surface to outer space. Most launch vehicles operate from a launch pad, launch pads, supported by a missile launch contro ...
. The Expedition-1 is an independent upper stage
A multistage rocket or step rocket is a launch vehicle that uses two or more rocket ''stages'', each of which contains its own engines and propellant. A ''tandem'' or ''serial'' stage is mounted on top of another stage; a ''parallel'' stage is ...
capable of delivering one or more spacecraft into different orbits. On 29 September 2015, the 20th satellite was launched, carrying a hydrogen maser
A hydrogen maser, also known as hydrogen frequency standard, is a specific type of maser that uses the intrinsic properties of the hydrogen atom to serve as a precision frequency reference.
Both the proton and electron of a hydrogen atom have sp ...
for the first time within the system.
In 2016, the 21st, 22nd and 23rd satellites were launched from Xichang Satellite Launch Center
The Xichang Satellite Launch Center (XSLC), also known as the Xichang Space Center, is a spaceport of China. It is located in Zeyuan Town (), approximately northwest of Xichang, Liangshan Yi Autonomous Prefecture in Sichuan.
The facility beca ...
, the last two of which entered into service on 5 August 2016 and 30 November 2016, respectively.
See also
* Chinese coordinate systems
References
External links
*
{{DEFAULTSORT:Beidou Navigation System
Navigation satellite constellations
Space program of the People's Republic of China
Satellites of China
Spacecraft launched by Long March rockets