BeiDou

The official English name of the system is BeiDou Navigation Satellite System. It is named after the Big Dipper 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. Historically, this set of stars was used in navigation to locate the North Star. 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 and his colleagues in the 1980s. The Gulf War in 1991 showcased how the GPS gave the US complete advantage on the battlefield and how satellite navigation systems can be used to conduct "space warfare". In 1993, China realised the risk of denied access to GPS during the Yinhe incident and including an alleged case in 1996 during the Third Taiwan Strait Crisis, gave impetus to the creation of its own indigenous satellite navigation system which officially began in 1994. According to the China National Space Administration, in 2010, the development of the system would be carried out in three steps: 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 rocket on 17 January 2010. 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 geosynchronous orbit) satellite, was launched from the Xichang Satellite Launch Center by a Long March 3A on 1 December 2011 (UTC). Chinese involvement in Galileo system In September 2003, China intended to join the European Galileo positioning system 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. Based on the Sino-European Cooperation Agreement on Galileo program, China Galileo Industries (CGI), the prime contractor of 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 the EU. Phase III • In November 2014, BeiDou became part of the World-Wide Radionavigation System (WWRNS) at the 94th meeting of the International Maritime Organization (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 rocket. • On 20 April 2019, a BeiDou satellite was successfully launched. Launch occurred at 22:41 Beijing time, 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 and the European Galileo positioning system, as well as the US's GPS. Use outside China , Indonesia (2025) In 2018, the Pakistan Armed Forces received access to BeiDou for military purposes. In 2019, the Saudi Ministry of Defense signed an agreement for military use of BeiDou. In 2021, the first China-Africa BeiDou System Cooperation Forum was held in Beijing. Use in smartphones Chinese smartphone maker Xiaomi featured BeiDou as early as August 2014, on their Mi 4. The earliest known smartphone by South-Korean smartphone maker Samsung to feature BeiDou is the Samsung Galaxy Note 4, released in October 2014. At a similar time, Japanese phone maker Sony implemented BeiDou for the first time on their Xperia Z3. The earliest BeiDou-capable smartphone by American smartphone maker Apple is the iPhone 13, released in September 2021. == GPS vs. BeiDou Capabilities ==

The National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board, which offers independent guidance to the U.S. government on GPS policy, issued a summary report from its 27th meeting held on 16–17 November 2022. During the meeting, it was highlighted that "GPS’s capabilities are now substantially inferior to those of China’s BeiDou." == BeiDou-3 ==

used by 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 (1191.79MHz), B3I/B3Q/B3A (1268.52MHz), and Bs test frequency (2492.02MHz). Interface control documents on the new open signals were published in 2017–2018. 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. BDS-3 satellites also include SBAS (B1C, B2a, B1A - GEO sats), Precise Point Positioning (B2b - GEO sats), and search and rescue transponder (6 MEOSAR) 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 broadcast called "Bs" at 2492.028 MHz, As of early 2022, China had 49 operational positioning, navigation, and timing satellites to provide coverage through the Beidou system. == Predecessors ==

BeiDou-1 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 geostationary communications satellite and had a launch weight of 1,000 kg each. Unlike the American GPS, Russian GLONASS, and European Galileo systems, which use medium Earth orbit satellites, BeiDou-1 used 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. 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. 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. • As of October 2009, all Chinese border guards in Yunnan were equipped with BeiDou-1 devices. Sun Jiadong, 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 , Galileo, and COMPASS; the light red color of E1 band indicates that the transmission in this band has not yet been detected. BeiDou-2 (formerly known as COMPASS) 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. All BeiDou satellites are equipped with laser retroreflector arrays for satellite laser ranging 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 and military. 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 (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. 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 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°. 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. Operation of BeiDou-M5 (2012-050A) 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 metres 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 metres 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. The new-generation BeiDou satellites support short message service. The system became operational in the China region that same month. As of December 2012, 16 satellites for BeiDou-2 had been launched, with 14 in service. As of December 2017, 150 million Chinese smartphones (20% of the market) were equipped to utilize BeiDou. == Constellations ==

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, In 2016, the 21st, 22nd and 23rd satellites were launched from Xichang Satellite Launch Center, the last two of which entered into service on 5 August and 30 November, respectively. Orbital period: 12 hours and 53 minutes (every 13 revolutions, done in 7 sidereal days, a satellite passes over the same location). == Concerns and prohibitions ==

Concerns have been raised by Taiwan's Ministry of Science and Technology about the possibility of embedded malware in BeiDou-enabled hardware and software. In 2018, Taiwan's National Communications Commission announced that it would be illegal to use BeiDou products in Taiwan without its approval. == See also ==