Beidou (Big Dipper / COMPASS)
The Compass/BeiDou Navigation Satellite System can provide two types of service at the global level: open service and authorized service. Through its open service, it provides free positioning, velocity and timing services. Through its authorized service, it provides safer positioning, velocity and timing services, as well as system integrality information, for authorized users. The Compass/BeiDou Navigation Satellite System can provide two kinds of authorized services, including a wide-area differential service (with a positioning accuracy of 1 m) and a short-message communication service in China and nearby areas.
China's indigenous satellite navigation system Beidou started providing initial operational services, including positioning, navigation and timing, to China and its surrounding areas from Tuesday 27 December 2011. According to plans, six more satellites were launched in 2012 to further expand the service area of Beidou system to most parts of Asia-Pacific region. Based on "three-step" development plan - from experimental system to regional system and then to global system, by 2011 China planned to continue building its Beidou satellite navigation system, implementing a regional Beidou satellite navigation system before 2012, whose navigation and positioning, timing and short-message services would cover the Asia-Pacific region. China aimed at completing the global Beidou satellite navigation system by 2020, comprising five GEO satellites and 30 non-GEO satellites.
The BeiDou Navigation Satellite System followed the development roadmap of starting with regional services first and expanding to global services later. A three-step development strategy was taken. Phase I is BeiDou Navigation Satellite Demonstration System, which was been established in 2000. Phase II is BeiDou Navigation Satellite (regional) System to provide service for areas in China and its surrounding areas from 2012. Phase III is BeiDou Navigation Satellite System to be established completely and provide global service by 2020. The regional Beidou system, which China refers to as Beidou-2, grew out of an earlier satellite constellation, known as Beidou-1. Beidou-1 provided limited precision, navigation, and timing services in China and a small portion of East Asia but served primarily as a developmental platform for future projects.
On December 27, 2012, China’s Beidou regional satellite navigation system became fully operational and available for commercial use. Using 16 satellites and a network of ground stations, Beidou provides subscribers in Asia with 24-hour precision, navigation, and timing services, as well as the ability to send and receive text messages up to 120 Chinese characters. China’s Satellite Navigation Office emphasized Beidou’s importance to the PLA and Chinese commercial interests, stating the system meets the ‘‘demands of China’s national security, economic development, technological advances and social progress . . . safeguard[s] national interests . . . enhance[s] the comprehensive national strength . . . promote[s] the development of satellite navigation industry . . . make[s] contributions to human civilization and social development . . . [and] serve[s] the world and benefit[s] mankind.’’
The nominal constellation of BeiDou Navigation Satellite (regional) System is composed of fourteen satellites, including five Geostationary Earth Orbit (GEO) satellites and nine Non-Geostationary Earth Orbit (Non-GEO) satellites. The Non-GEO satellites include four Medium Earth Orbit (MEO) satellites and five Inclined Geosynchronous Satellite Orbit (IGSO) satellites. The GEO satellites are positioned at 58.75°E, 80°E, 110.5°E, 140°E and 160°E respectively. The B1 signal is the sum of channel I and Q which are in phase quadrature of each other. The ranging code and navigation message is modulated on B1 carrier signal. The signal is composed of the carrier frequency, ranging code and navigation message.
Ground control segment consists of several Master Control Stations (MCS), Upload Stations (US) and a network of globally distributed Monitor Stations (MS). The main tasks of MCS are to collect observing data from each MS, to process data, to generate satellite navigation messages, wide area differential data and integrity information, to perform mission planning and scheduling, and to conduct system operation and control. The main tasks of Upload Stations include completing the upload of satellite navigation messages, wide area differential data and integrity information, controlling and managing the payload. The tasks of Monitor Stations include continuous tracking and monitoring ofnavigation satellites, receiving navigation signals, sending observational data to the Master Control Station for the satellitesorbit determination and time synchronization. The user terminals include various BeiDou user terminals, and terminals compatible with other navigation satellite systems.
The Beidou satellite navigational system provides positional information for highway, railway and marine transportation. The three satellites have formed a complete satellite navigation and positioning system, which will help to ensure all-weather navigation and positioning information. The China-made system will play an important role in economic matters, offering efficient navigation and positioning services for the sectors of transportation, meteorology, petroleum production, forest fire prevention, disaster forecast, telecommunications and public security. The navigation system, which serves as a radio beacon in outer space, can help subscribers know their location at any time and place with accurate longitude, latitude and altitude data.
China based the Bei Dou satellites on the three-axis stabilized DFH-3 satellite bus, to deliver services such as power and attitude control. China is one of the few countries in the world capable of developing such a system on its own, and has also made some innovations in the positioning property of the system. Both the satellite and carrier rocket were developed by the Chinese Research Institute of Space Technology and China Academy of Launch Vehicle Technology, which are under the China Space Science and Technology Group. New testing procedures were adopted in the launch, which not only help reduce the time needed for preparing for the launch, but also improve the quality of the carrier rocket, enabling China to be at the forefront in this field around the world, said the experts.
The precise nature of this system was initially somewhat obscure, but it initially appeared to be analogous to the Wide Area Augmentation System [WAAS] implemented in the United States to supplement the Global Positioning System. In the American WAAS, a network of precisely surveyed ground reference stations receive GPS signals, which determine if errors exist and compute corrections. These corrections are then transmitted from a geo-stationary communication satellite on the same frequency as GPS. This could enable China to continue to use the American GPS system, even in the face of American efforts to deny GPS to adversaries in wartime.
In early 1980s, China began to actively study the navigation satellite systems in line with China’s conditions. In 1994, under the framework of International Telecommunication Union (ITU), China started the BeiDou Navigation Satellite System frequency coordination activities. Satellite network information was submitted in accordance with the BeiDou system construction plan and progress. China, as a member of the International Committeeon Global Navigation Satellite Systems (ICG), has participated in every ICG General Assembly Meeting and the ICG Providers Forum. In 2007, China became one of the four core providers designated by the organization.
In 2000, BeiDou Navigation Demonstration System was basically established, which made China the third nation in possession of an independent navigation satellite system following the United States and Russia. The Beidou (Big Dipper) Navigation Test Satellite 1 (BNTS-1) was launched by a Chinese Long March 3M booster on 31 October 2000, into a geo-stationary orbit slot at 140 degrees East Longitude, to the east of China. It was followed by "Beidou 1B" on 21 December 2000, which was placed in a geo-stationary slot at 80 degrees East longitude. Beidou 1C was launched into an orbit at at 110.5°E on 24 May 2003 from the Xichang Satellite Launch Center on a CZ-3A booster. With this third launch, China claimed to have completed a constellation of three navigational satellites.
The demonstration system can provide positioning, timing and short-message communication services to users in China and nearby areas. Besides, a GPS augmentation function is included. The system has been applied to many fields including geodesy and surveying, communication, fishing, mineral prospecting, forest fire prevention, national security etc. The system played a significant role in rescue and relief efforts during the ice-snow disaster that took place in southern China and in the Wenchuan earthquake that struck Sichuan province in 2008.
On 14 April 2007, the first MEO satellite, named Compass-M1, was launched. On 15 April 2009, the first geostationary satellite, named Compass-G2, was launched. According to the construction schedule, the Compass/BeiDou Navigation Satellite System will, as a first step, cover China and the nearby area, by around 2011, but the full deployment of the System will be completed between 2015 and 2020.
In January 2009 China announced that it expected to complete its own independent Bei dou Navigation System (BNS) GPS Satellite system by the year 2015. It is expected to consist of 30 satellite ten of which are to be launched during 2009-2010 in addition to the five already in place.
The PRC launched the second of its duel purpose Bei dou "Compass," navigation system (BNS) satellites on April 15, 2009 with a Long March-3C booster stating that it was a "Critical part of the space infrastructure". It pending launch was announced from the Xichang Space Launch Center on April 12th. A total of ten satellites are supposed to be orbited by the end of 2010. The U. S. Government prior to this launched credited the PRC as having flown five of these kinds of satellites." (3)
The PRC launched the third second generation of its duel purpose military civil Bei dou "Compass," navigation system (BNS) satellites on January 15, 2010 with a Long March-IIIC booster stating that it was a "Critical part of the space infrastructure". It pending launch was announced from the Xichang Space Launch Center on January 15, 2010. China's regional navigation service was originally scheduled for completion with 10 satellites in 2010 but that has now slipped into early 2012. The number of satellites for the full system is expected to be not 30 but 35 satellites by 2020 with 30 in the lower none geo-stationary orbit. Its major role will be utilized for information national security uses and other economic activities. (4)
The PRC launched the fourth second generation of its duel purpose military civil Bei dou "Compass," navigation system (BNS) satellites on June 2, 2010 with a Long March-3C booster stating that it was a "Critical part of the space infrastructure". It pending launch was announced from the Xichang Space Launch Center on June 1, 2010.References: (5) This leaves eight more Bei dou "Compass," satellite to be launched by early in 2012 by splitting the program between two five year plans. The rest of the program is also being split over two additional five year plans with the obvious reality that some of the spacecraft with shorter life times will also have to be replaced eventually. To this end China launched another of its Long March -3A boosters on late July 31, 2010 with the fifth launch of its second generation Biedou global positioning satellite to add to the developing constellation.
Since it was officially brought into service in 2003, the BeiDou Navigation Satellite Demonstration System has been widely used in transportation, marine fisheries, hydrological monitoring, weather forecasting, forest fire prevention, timing for communication systems, power distribution, disaster mitigation, national security, and many other fields, which has been resulting in significant social and economic benefits. Particularly, the system has played an important role in the South China frozen disaster, earthquake relief in Wenchuan, Sichuan Province and Yushu, Qinghai Province, theBeijing Olympic Games, and the Shanghai World Expo.
On December 27, 2012, China announced that BeiDou System would formally provide Full Operational Service for China and its surrounding areas since then. The service performances of BeiDou System in China and its surrounding areas are as follows:
- Service Area: from 55 degree south latitude to 55 degree north latitude, and from 55 to 180 degree east longitude;
- Positioning Accuracy: Horizontally, 10 meters, and vertically, 10 meters;
- Velocity Accuracy: 0.2 meters per second;
- Timing Accuracy: one-way, 50 nanoseconds.
China's homegrown Beidou Navigation Satellite System would be put into its first oversea operation in Thailand early in 2014r. The announcement was made in Bangkok in October 2013 by China's Wuhan Information Technology Outsourcing Service and Research Centre and the Geo-informatics and Space Technology Development Agency (GISTDA) under Thailand's Ministry of Science and Technology. An agreement with an expected value of 319 million U.S. dollars inked by the two countries in March has established their commitment to cooperation on the construction of Thailand's geospatial system, giving the country access to China's advanced technology, products and services. The two sides have agreed to start building a model satellite station based on Beidou in an industrial estate in Thailand's eastern Chon Buri province next month and nationwide construction will begin early next year, said Liu Junyi, deputy director of the Wuhan Information Technology Outsourcing Service and Research Centre.
It will be the first time that the Beidou lands outside China, said Liu, adding that China will draw experience in its cooperation with Thailand and further explore foreign markets. " The Beidou will be able to provide global service by 2015," he said.
1. Hodgin, Rick C., Trend watch, Tgdaily.com, http://www.thdaily.com, January 19, 2009, p. 1-2.
2. China to have global satellite navigation system by 2015, China View, http://news.xinhuanet.com, January 19, 2009 p. 1.
3. China launches 2nd satellite in GPS system, Beijing Associated Press, April 15, 2009 p. 1. & China daily.com.cn.
4. China to send third navigation satellite into orbit, http://news.xinhuanet.com January 15, 2010 & China Launches Third Orbiter For Indigenous Global SatNav System Xichang, China Jan 18, 2010 GPS Daily & China opens 2010- with BeiDou-2 Satellite launch, NASA Spqaceflight.com January 16, 2010.
5. China To Launch Fourth Orbiter For Global Satellite Navigation Network Xichand, China June 2, 20109 GPS Daily, & China sends Beidou navigation satellite to orbit, Spaceflight Now June 2, 2010.
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