BeiDou_Navigation_Satellite_System

context: The BeiDou Navigation Satellite System (BDS, simplified Chinese: 北斗卫星导航系统; traditional Chinese: 北斗衛星導航系統; pinyin: Běidǒu wèixīng dǎoháng xìtǒng) is a Chinese satellite navigation system. It consists of two separate satellite constellations – a limited test system that has been operating since 2000, and a full-scale global navigation system that is currently under construction.
qas: answers: text: a Chinese satellite navigation system
question: What is the BeiDou Navigation Satellite System?

answers: text: two separate satellite constellations
question: How many satellite constellations does the BeiDou Navigation Satellite System have?

answers: text: a limited test system that has been operating since 2000, and a full-scale global navigation system
question: What are the two satellite constellations?

answers: text: since 2000
question: How long has the limited test system been operating?

answers: text: 北斗衛星導航系統
question: How is the BeiDou Navigation Satellite System written in traditional Chinese?

context: The first BeiDou system, officially called the BeiDou Satellite Navigation Experimental System (simplified Chinese: 北斗卫星导航试验系统; traditional Chinese: 北斗衛星導航試驗系統; pinyin: Běidǒu wèixīng dǎoháng shìyàn xìtǒng) and also known as BeiDou-1, consists of three satellites and offers limited coverage and applications. It has been offering navigation services, mainly for customers in China and neighboring regions, since 2000.
qas: answers: text: the BeiDou Satellite Navigation Experimental System
question: What was the first BeiDou system called?

answers: text: mainly for customers in China and neighboring regions
question: Who does the BeiDou-1 operate for?

answers: text: BeiDou-1
question: What is another name for the BeiDou Satellite Navigation Experimental System?

answers: text: three
question: How many satellites does the BeiDou-1 have?

answers: text: since 2000
question: How long has the BeiDou-1 been operating?

context: The second generation of the system, officially called the BeiDou Navigation Satellite System (BDS) and also known as COMPASS or BeiDou-2, will be a global satellite navigation system consisting of 35 satellites, and is under construction as of January 2015[update]. It became operational in China in December 2011, with 10 satellites in use, and began offering services to customers in the Asia-Pacific region in December 2012. It is planned to begin serving global customers upon its completion in 2020.
qas: answers: text: BeiDou Navigation Satellite System
question: What is the name of the second generation of BDS?

answers: text: COMPASS or BeiDou-2
question: What is another name for the BeiDou Navigation Satellite System?

answers: text: 35
question: How many satellites will the BeiDou-2 have?

answers: text: January 2015
question: When did the BeiDou-2 begin construction?

answers: text: December 2011
question: When did the BeiDou-2 begin operating?

context: In-mid 2015, China started the build-up of the third generation BeiDou system (BDS-3) in the global coverage constellation. The first BDS-3 satellite was launched 30 September 2015. As of March 2016, 4 BDS-3 in-orbit validation satellites have been launched.
qas: answers: text: mid 2015
question: When did China begin constructing the third BeiDou system?

answers: text: BDS-3
question: What is the third BeiDou system called?

answers: text: 30 September 2015
question: When was the first BDS-3 satellite launched?

answers: text: 4
question: How many BDS-3 satellites have been launched?

context: According to China daily. Fifteen years after the satellite system was launched, it is now generating $31.5 billion for major companies such as China Aerospace Science and Industry Corp, AutoNavi Holdings Ltd, and China North Industries Group Corp.
qas: answers: text: Fifteen years
question: How long ago was the BeiDou Satellite System first launched?

answers: text: $31.5 billion
question: How much revenue for companies is generated by the BDS system?

answers: text: China Aerospace Science and Industry Corp, AutoNavi Holdings Ltd, and China North Industries Group Corp.
question: What are some companies that profit from the BDS system?

context: The official English name of the system is BeiDou Navigation Satellite System. It is named after the Big Dipper constellation, which is known in Chinese as Běidǒu. The name literally means "Northern Dipper", the name given by ancient Chinese astronomers to the seven brightest stars of the Ursa Major constellation. Historically, this set of stars was used in navigation to locate the North Star Polaris. As such, the name BeiDou also serves as a metaphor for the purpose of the satellite navigation system.
qas: answers: text: the Big Dipper constellation
question: What is the BeiDou Navigation Satellite System named after?

answers: text: Běidǒu
question: What is the Big Dipper constellation known as in Chinese?

answers: text: Northern Dipper
question: What does Běidǒu translate as?

answers: text: ancient Chinese astronomers
question: Who named the constellation Běidǒu?

answers: text: to locate the North Star Polaris
question: What was the Běidǒu constellation used for?

context: The original idea of a Chinese satellite navigation system was conceived by Chen Fangyun and his colleagues in the 1980s. According to the China National Space Administration, the development of the system would be carried out in three steps:
qas: answers: text: Chen Fangyun and his colleagues
question: Who first came up with the idea for a Chinese satellite navigation system?

answers: text: in the 1980s
question: When did Chen Fangyun come up with the idea for a satellite navigation system?

answers: text: three
question: The China National Space Administration said the satellite navigation system would be developed in how many steps?

context: 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.
qas: answers: text: BeiDou-1A
question: What was the name of the first satellite launched for the system?

answers: text: 20 December 2000
question: When was BeiDou-1A launched?

answers: text: BeiDou-1C
question: What was the name of the third satellite launched for the system?

answers: text: a backup satellite
question: What was the purpose of launching the BeiDou-1C satellite?

answers: text: 25 May 2003
question: When was the BeiDou-1C satellite launched?

context: On 2 November 2006, China announced that from 2008 BeiDou would offer an open service with an accuracy of 10 meters, timing of 0.2 microseconds, and speed of 0.2 meters/second.[citation needed]
qas: answers: text: 2 November 2006
question: When did China announce service plans for the BeiDou system?

answers: text: 10 meters
question: What was the accuracy range that China promised to offer in 2008 with the BeiDou system?

answers: text: timing of 0.2 microseconds, and speed of 0.2 meters/second
question: What was the timing and speed that China promised to offer in 2008 with the BeiDou system?

context: 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 sent up into space. It was reported that the satellite had suffered from a control system malfunction but was then fully restored.
qas: answers: text: February 2007
question: When was the fourth satellite for the BeiDou-1 system launched?

answers: text: BeiDou-1D
question: What is the name of the fourth BeiDou-1 satellite?

answers: text: BeiDou-2A
question: What is the BeiDou-1D satellite sometimes called?

answers: text: serving as a backup satellite
question: What is the purpose of the BeiDou-1D satellite?

answers: text: a control system malfunction
question: What happened to the BeiDou-1D satellite that needed to be repaired?

context: 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 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 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 geosynchonous orbit) satellite, was launched from the Xichang Satellite Launch Center by a Long March-3A on 1 December 2011 (UTC).
qas: answers: text: April 2007
question: When was the first satellite for the BeiDou-2 system launched?

answers: text: Compass-M1
question: What is the the first satellite for the BeiDou-2 system called?

answers: text: to validate frequencies for the BeiDou-2 constellation
question: What is the purpose of the Compass-M1 satellite?

answers: text: 15 April 2009
question: When was the second satellite for the BeiDou-2 system launched?

answers: text: 17 January 2010
question: When was the third satellite for the BeiDou-2 system launched?

context: In September 2003, China intended to join the European Galileo positioning system project and was to invest €230 million (USD296 million, GBP160 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 reported in January 2008 that China was unsatisfied with its role in the Galileo project and was to compete with Galileo in the Asian market.
qas: answers: text: €230 million (USD296 million, GBP160 million)
question: How much was China going to invest in the European Galileo positioning system project?

answers: text: only be used by its armed forces
question: In 2003, what was the planned purpose of the BeiDou navigation system?

answers: text: October 2004
question: When did China join the Galileo project?

answers: text: December 2004
question: When was China Galileo Industries (CGI) founded?

answers: text: the Hong Kong-based South China Morning Post
question: Who said in 2008 that China was unsatisfied with its involvement in the Galileo project?

context: BeiDou-1 is an experimental regional navigation system, which consists of four satellites (three working satellites and one backup satellite). The satellites themselves were based on the Chinese DFH-3 geostationary communications satellite and had a launch weight of 1,000 kilograms (2,200 pounds) each.
qas: answers: text: an experimental regional navigation system
question: What is the BeiDou-1?

answers: text: four
question: The BeiDou-1 is made up of how may satellites?

answers: text: one
question: How many satellites in the BeiDou-1 system is used for back up?

answers: text: the Chinese DFH-3 geostationary communications satellite
question: What were the BeiDou-1 system satellites based on?

answers: text: 1,000 kilograms (2,200 pounds) each
question: How much did each satellite for the BeiDou-1 system weigh?

context: Unlike the American GPS, Russian GLONASS, and European Galileo systems, which use medium Earth orbit satellites, BeiDou-1 uses satellites in geostationary orbit. 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.
qas: answers: text: medium Earth orbit satellites
question: What type of satellites does the American GPS system use?

answers: text: satellites in geostationary orbit
question: What type of satellites does the BeiDou-1 system use?

answers: text: the system does not require a large constellation of satellites
question: What is the purpose of the BeiDou-1 system using stallites in geostationary orbit?

answers: text: from longitude 70°E to 140°E and from latitude 5°N to 55°N
question: What service area is covered by the BeiDou-1 system?

answers: text: 2491.75 MHz
question: What is the frequency of the BeiDou-1 system?

context: The first satellite, BeiDou-1A, was launched on October 31, 2000. The second satellite, BeiDou-1B, was successfully launched on December 21, 2000. The last operational satellite of the constellation, BeiDou-1C, was launched on May 25, 2003.
qas: answers: text: October 31, 2000
question: When was the first satellite for the BeiDou-1 system launched?

answers: text: BeiDou-1A
question: What was the first satellite for the BeiDou-1 system called?

answers: text: December 21, 2000
question: When was the second satellite for the BeiDou-1 system launched?

answers: text: BeiDou-1B
question: What was the second satellite for the BeiDou-1 system called?

answers: text: May 25, 2003
question: When was the last satellite for the BeiDou-1 system launched?

context: In 2007, the official Xinhua News Agency reported that the resolution of the BeiDou system was as high as 0.5 metres. With the existing user terminals it appears that the calibrated accuracy is 20m (100m, uncalibrated).
qas: answers: text: as high as 0.5 metres
question: In 2007, what was the reported resolution of the BeiDou system?

answers: text: 20m
question: What is the calibrated accuracy of the BeiDou system?

answers: text: 100m
question: What is the uncalibrated accuracy of the BeiDou system?

answers: text: the official Xinhua News Agency
question: Who reported the resolution of the BeiDou system in 2007?

context: In 2008, a BeiDou-1 ground terminal cost around CN¥20,000RMB (US$2,929), 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, a BeiDou terminal priced at CN¥3,000RMB was presented.
qas: answers: text: around CN¥20,000RMB (US$2,929)
question: How much did a BeiDou-1 ground terminal cost in 2008?

answers: text: almost 10 times the price
question: How much more did a BeiDou-1 ground terminal cost than a current GPS terminal?

answers: text: due to the cost of imported microchips
question: Why is a BeiDou-1 ground terminal so expensive?

answers: text: Shenzhen
question: Where was the ELEXCON fair held in 2009?

answers: text: a BeiDou terminal priced at CN¥3,000RMB
question: What was presented at the ELEXCON fair in 2009?

context: According to Sun Jiadong, the chief designer of the navigation system, "Many organizations have been using our system for a while, and they like it very much."
qas: answers: text: Sun Jiadong
question: Who is the chief designer of the BeiDou navigation system?

answers: text: "Many organizations have been using our system for a while, and they like it very much."
question: What did Sun Jiadong have to say about the BeiDou navigation system?

answers: text: the chief designer of the navigation system
question: Who is Sun Jiadong?

context: BeiDou-2 (formerly known as COMPASS) is not an extension to the older BeiDou-1, but rather supersedes it outright. The new system will be 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 and 3 in inclined geosynchronous orbit), that will offer complete coverage of the globe.
qas: answers: text: COMPASS
question: What was the BeiDou-2 system previously known as?

answers: text: 35
question: How may satellites will the BeiDou-2 system have?

answers: text: 5
question: How many geostationary orbit satellites will the BeiDou-2 system have?

answers: text: 30
question: How many non-geostationary orbit satellites will the BeiDou-2 system have?

answers: text: for backward compatibility with BeiDou-1
question: What is the purpose of the geostationary orbit satellites in the BeiDou-2 system?

context: The ranging signals are based on the CDMA principle and have complex structure typical of Galileo or modernized GPS. Similar to the other GNSS, there will be two levels of positioning service: open and restricted (military). The public service shall be available globally to general users. When all the currently planned GNSS systems are deployed, the users will benefit from the use of a total constellation of 75+ satellites, which will significantly improve all the aspects of positioning, especially availability of the signals in so-called urban canyons. The general designer of the COMPASS navigation system is Sun Jiadong, who is also the general designer of its predecessor, the original BeiDou navigation system.
qas: answers: text: the CDMA principle
question: What are the ranging signals of the BeiDou system based on?

answers: text: open and restricted (military)
question: What positioning levels will the BeiDou system offer?

answers: text: globally to general users
question: Where will the public service for the BeiDou system be available?

answers: text: Sun Jiadong
question: Who designed the COMPASS navigation system?

answers: text: 75+ satellites
question: How many satellites will the COMPASS navigation system use?

context: There are two levels of service provided — a free service to civilians and licensed service to the Chinese government and military. The free civilian service has a 10-meter 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 centimetres, can be used for communication, and will supply information about the system status to the user. To date, the military service has been granted only to the People's Liberation Army and to the Military of Pakistan.
qas: answers: text: a free service to civilians and licensed service to the Chinese government and military
question: What types of services will be offered by the BeiDou system?

answers: text: 10-meter location-tracking accuracy
question: What is the range of accuracy for the free service offered to civilians?

answers: text: 10 centimetres
question: What is the range of accuracy for the licensed service used by Chinese government and military?

answers: text: the People's Liberation Army and to the Military of Pakistan
question: As of right now, who uses the licensed military service?

answers: text: communication
question: What is something the licensed military service can be used for?

context: Frequencies for COMPASS are allocated in four bands: E1, E2, E5B, and E6 and 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 inter-system interference, especially within E1 and E2 bands, which are allocated for Galileo's publicly regulated service. However, under International Telecommunication Union (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. It now appears that Chinese COMPASS satellites will start transmitting in the E1, E2, E5B, and E6 bands before Europe's Galileo satellites and thus have primary rights to these frequency ranges.
qas: answers: text: four bands
question: How many frequencies does the COMPASS system use?

answers: text: E1, E2, E5B, and E6
question: What are the four bands of frequencies used by the COMPASS system called?

answers: text: E1 and E2
question: Which frequency bands are most likely to cause issues of inter-system interference with the Galileo system?

answers: text: E1 and E2
question: Which bands are used by the Galileo system for their public service?

answers: text: the first nation to start broadcasting in a specific frequency
question: According to International Telecommunication Union (ITU) policies, who is given higher priority to a specific frequency band?

context: 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.
qas: answers: text: little was officially announced
question: How much information about the COMPASS system did Chinese authorities release?

answers: text: to study general characteristics of the signals
question: What is one thing launching the first COMPASS satellite enable researchers to do?

answers: text: to build a COMPASS receiver
question: What is another thing launching the first COMPASS satellite enable researchers to do?

context: 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 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 degrees.
qas: answers: text: 14 April 2007
question: When was the Compass-M1 satellite launched?

answers: text: for signal testing and validation and for the frequency filing
question: What is the purpose of the Compass-M1 satellite?

answers: text: the GIOVE satellites for the Galileo system
question: The purpose of the Compass-M1 satellite is similar to the purpose of what other satellite?

answers: text: 21,150 km
question: What is the altitude of the Compass-M1 satellite?

answers: text: 55.5 degrees
question: What is the inclination of the Compass-M1 satellite?

context: 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 degrees (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. IQ modulation has been the method in both wired and wireless digital modulation since morsetting carrier signal 100 years ago.
qas: answers: text: E2, E5B, and E6
question: What frequency bands does Compass-M1 transmit in?

answers: text: 90 degrees (in quadrature)
question: What is the phase shift of the sub-signals detected in each frequency band used by  Compass-M1?

answers: text: "I" and "Q"
question: What are the two sub-signals in each frequency band referred to as?

answers: text: likely to be intended for the open service
question: What is the intended purpose of the "I" component?

answers: text: probably intended for the restricted service
question: What is the intended purpose of the "Q" component?

context: 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 reported the spectrum and structure of the signals. A month later, researchers from Stanford University reported the complete decoding of the “I” signals components. The knowledge of the codes allowed a group of engineers at Septentrio to build the COMPASS receiver and report tracking and multipath characteristics of the “I” signals on E2 and E5B.
qas: answers: text: immediately after the launch of Compass -M1 on 14 April 2007
question: When did the investigation of the signals transmitted by Compass -M1 begin?

answers: text: the spectrum and structure of the signals
question: What did engineers at CNES report in June 2007?

answers: text: researchers from Stanford University
question: Who reported the complete decoding of the “I” signals components?

answers: text: a group of engineers at Septentrio
question: Who built the COMPASS receiver?

answers: text: report tracking and multipath characteristics of the “I” signals on E2 and E5B
question: What was the purpose of building the COMPASS receiver?

context: 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 and is quoted in the first row of the table.
qas: answers: text: Compass signals have somewhat greater power
question: What is the difference between the "I" signals on E2 and E5B and the civilian codes of GPS (L1-CA and L2C)?

context: In December 2011, the system went into operation on a trial basis. It has started providing navigation, positioning and timing data to China and the neighbouring area for free from 27 December. During this trial run, Compass will offer positioning accuracy to within 25 meters, but the precision will improve as more satellites are 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 m per second, and provide signals for clock synchronisation accurate to 0.02 microseconds.
qas: answers: text: December 2011
question: When did the Compass system begin operation on a trial bases?

answers: text: 27 December
question: When did the Compass system begin offering navigation, positioning and timing data to China and nearby locations?

answers: text: as more satellites are launched
question: What will improve the positioning accuracy of the Compass system?

answers: text: accurate to the nearest 10 m
question: Upon launching, the Compass system, what was the location accuracy promised to users?

answers: text: within 0.2 m per second
question: Upon launching, the Compass system, what was the speed promised to users?

context: 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.
qas: answers: text: December 2012
question: When did the BeiDou-2 system start offering services?

answers: text: the Asia-Pacific region
question: Where did the BeiDou-2 system start offering services in 2012?

answers: text: between longitude 55°E to 180°E and from latitude 55°S to 55°N
question: At the time when BeiDou-2 system began offering services, what was the positioning data the system was able to provide?

context: In December 2011, Xinhua stated that "[t]he 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 have been launched, 14 of them are in service.
qas: answers: text: December 2011
question: When did the Beidou system begin operating in China?

answers: text: by 2020
question: When is it projected that the global navigation system will be finished?

answers: text: 16
question: As of December 2012, how many satellites had been launched for the BeiDou-2 system?

answers: text: 14
question: Of the 16 satellites launched for the BeiDou-2 system, how many are operational?

context: 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.
qas: answers: text: 2007
question: When was the Compass-M1 satellite launced?

answers: text: nine
question: How many satellites were launched from 2009-2011?

answers: text: functional regional coverage
question: What was achieved by launching 9 additional satellites from 2009-2011?

answers: text: 16
question: How many satellites were launched since 2007?

context: 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.
qas: answers: text: 2015
question: When did the BeiDou system begin transitioning to global coverage?

answers: text: with the first launch of a new-generation of satellites
question: How did the BeiDou system begin transitioning to global coverage?

context: On July 25, 2015, the 18th and 19th satellites were successfully launched from the Xichang Satellite Launch Center, marking the first time for China to launch two satellites at once on top of a Long March 3B/Expedition-1 carrier rocket. The Expedition-1 is an independent upper stage capable of delivering one or more spacecraft into different orbits.
qas: answers: text: July 25, 2015
question: When were the 18th and 19th satellites for the BeiDou system launched?

answers: text: the Xichang Satellite Launch Center
question: Where were the 18th and 19th satellites for the BeiDou system launched from?

answers: text: Long March 3B/Expedition-1 carrier rocket
question: What were the 18th and 19th satellites for the BeiDou system launched with?

answers: text: an independent upper stage capable of delivering one or more spacecraft into different orbits
question: What is the Expedition-1?

context: The three latest satellites will jointly undergo testing of a new system of navigation signaling and inter-satellite links, and start providing navigation services when ready.
qas: answers: text: navigation services
question: What will the three latest satellites provide after testing?

answers: text: testing of a new system of navigation signaling and inter-satellite links
question: What kind of testing will be performed on the three latest satellites?

answers: text: three
question: How many satellites will be used to test a new system of navigation signaling?