China Satellite Navigation Office
INTRODUCTION OF THE BEIDOU NAVIGATION SATELLITE SYSTEM
The general development guideline of the BeiDou Navigation Satellite System (hereinafter in short the BeiDou system) includes quality, safety, application, and benefits. As a global satellite navigation system, the BeiDou system aims to provide all-day and all-weather navigation services of high performance and reliability for users around the world, with regional passive services coverage by 2012 and global passive services coverage by 2020.
The BeiDou system adopts four basic principles of openness, independence, compatibility, and gradualness.
Openness implies that the BeiDou system will provide high-quality open service free of charge for worldwide users and communicate with other countries to facilitate the development of GNSS technologies and industry.
Independence means that China will develop and operate the BeiDou system independently, provide services independently for worldwide users, and in particular provide high-quality services in the Asia-Pacific region.
Meanwhile, the BeiDou system will pursue solutions to realize compatibility and interoperability with other satellite navigation systems so that users can get better services with interoperable receivers, and so that the system can improve backward compatibility, ensuring the better interests and services of users and industries.
Based on the gradualness principle, the BeiDou system will follow a step-by-step pattern in accordance with technical and economic evolution in China, provide long-term continuous services for users, improve system performance, and ensure seamless and smooth transition between the system construction phases.
Figure 1 shows the overall development planning of the BeiDou system: “three-step” deployment, from regional to global, from active to passive.
In the 1980s, in line with the condition and demands of the time, China began to conduct a study on the BeiDou demonstration system under dual-satellite active positioning mechanism. First initiated in 1994, the BeiDou demonstration system was able to provide regional active services in 2000. From 2000 to 2003, three satellites were launched, and in 2010, these satellites have been replaced by new ones.
In 1999, China began to study the BeiDou navigation satellite system under passive positioning mechanism. System construction formally started in 2004. The system will provide radio navigation satellite service (RNSS) for users in China and its surrounding areas on the basis of radio determination satellite service (RDSS) from 2012.
The BeiDou system will finally provide compatible and interoperable RNSS with global coverage and also upgraded RDSS by 2020.
The BeiDou system is comprised of three major components: space segment, ground segment, and user segment. The space segment consists of 5 geostationary (GEO) satellites and 30 non-GEO satellites. The ground segment consists of several master control stations (MCS), upload stations (US), and a network of globally distributed monitor stations (MS). The user segment includes BeiDou terminals and interoperable terminals compatible with other GNSS systems, to meet different application requirements from different fields and industries.
The BeiDou system can transmit multiple navigation signals. Generally speaking, the system can provide two kinds of global services: open service and authorized service. Open service is free to users with positioning accuracy better than 10 m, timing accuracy better than 20 ns, and velocity accuracy of 0.2 m/s. The system can also provide two kinds of regional services—wide-area differential service and short message service. Wide-area differential accuracy is better than 1 m.
The time reference for the BeiDou system uses BeiDou time (BDT), which is traceable to the Coordinated Universal Time (UTC) maintained by the National
FIGURE 1 Scheme of the BeiDou system.
Time Service Center (NTSC) of the Chinese Academy of Sciences. The coordinate framework of the BeiDou system adopts the China Geodetic Coordinate System 2000 (CGCS2000), which is consistent with the International Terrestrial Reference Frame (ITRF) at the 5 cm level.
BeiDou demonstration satellites have been operating for 10 years. In 2010, the Beidou demonstration system was seamlessly transferred to the Beidou navigation system, with its RDSS positioning, timing, and short-message communication services performances improved.
So far, the BeiDou system has made steady progress. From April 2007 to April 2011, eight satellites were launched to form “3+3” basic system except a part used for verification and signal testing and equipment R&D, as is shown by Table 1.
The first medium Earth orbit (MEO) satellite, named COMPASS-M1, was launched on April 14, 2007, and secured the International Telecommunications Union (ITU) related filing. As the first RNSS satellite, many technical experiments have been implemented with it.
The first GEO satellite, named COMPASS-G2, was launched on April 15, 2009. It was used for technical experiments such as GEO orbit determination and time synchronization. Now the satellite is in orbit. The second GEO satellite was launched on January 17, 2010. It was initially located at 160°E to secure the ITU-related filing but, after in-orbit test and experiment verification, it moved to 144.5°E and is now operating well. The third GEO satellite was launched on June 2, 2010. Initially located at 84.6°E to carry out in-orbit tests, it was moved to 84°E and now operates optimally. The fourth GEO satellite was launched on November 1, 2010, and is located at 160°E.
The first IGSO (inclined geosynchronous satellite orbit) satellite was launched on August 1, 2010; the intersection point is at 118°E. The second IGSO satellite was launched December 18, 2010, and the third IGSO satellite was launched on April 10, 2011.
TABLE 1 Launch Record of BeiDou Navigation Satellites
|Date||Type||Launch Site||Launch Carrier||Launch Cabin|
In addition, the installment and testing of ground segment components were completed and successfully realized functions. The system is able to provide initial positioning, navigation, and timing services for China and its surrounding areas.
APPLICATION OF BEIDOU NAVIGATION SATELLITE SYSTEM
From Construction to Application
Today, the BeiDou system has played an important role in many fields. It is widely used in transportation, marine fishery, hydrological monitoring, meteorological forecasting, forestry fire prevention, telecommunication and timing, power dispatching, and disaster mitigation and relief.
In disaster prevention and mitigation, the BeiDou system can help to improve rescue response and decision-making capability through broadcasting rapid and timely disaster alerts, scheduling rescue commands, and providing rapid emergency communication. Especially during the Southern China snowstorm and the earthquakes in Wenchuan, Sichuan Province, and Yushu, Qinghai Province, BeiDou terminals sent the disaster and rescue information to a command center in the first place and provided strong support to the search and rescue work.
From Application to Services
Through building an integrated BeiDou application system, the system can integrate national resources through demonstration in various trade sectors and regions and transit from single service into integrative service (Figure 2).
From Regional to Global
The applications of the BeiDou system will gradually extend from China to the Asia-Pacific region, and further extend to global by 2020 (Figure 3).
FIGURE 2 The application of BeiDou.
FIGURE 3 The coverage of BeiDou.
The BeiDou system adheres to the basic policy of opening up to the outside world and has actively engaged in international space cooperation. It supports all activities that utilize outer space for peaceful purposes and is dedicated to strong cooperation with other countries based on the equality, mutual benefit, and peaceful utilization of outer space and common development.
The international cooperation will be conducted in a phased, focused, non-discriminatory, and selective approach in accordance with the overall development plan of China’s navigation satellite system.
China’s international exchange and cooperation in the field of satellite navigation started in the 1990s. In nearly 20 years, various forms of activities have been carried out with extensive results.
In 1994, under the framework of the ITU, China started the BeiDou Navigation Satellite System frequency coordination activities. Satellite network information was submitted in accordance with the BeiDou system’s construction plan and progress.
The BeiDou system has actively participated in and supported cooperation in compatibility and interoperability of GNSS, monitoring and evaluation of the service performance of GNSS, the improvement of performance and technology in satellite navigation, GNSS applications, and GNSS international standards of civil aviation and maritime, as well as interference detection and mitigation of GNSS open services.
China has actively participated in bilateral frequency coordination meetings with the United States, the European Union (EU), and Russia. It held several meetings on compatibility and interoperability issues with the EU, attended international academic conferences and forums, such as: the ION annual conference in the United States, the European Navigation Conference, the Munich Satellite Navigation Summit, the World Radiocommunication Conference, and the meetings of ITU study groups and working groups. It also attended ICG-5 in October 2010, and the application for hosting ICG-7 in 2012 gained recognition by UNOOSA (United Nations Office for Outer Space Affairs) and ICG (International Committee on GNSS) members.
The construction and application of the BeiDou Navigation Satellite System is steadily progressing. The BeiDou system has been attaching great importance to cooperation with other countries to share experience and achievements and will continue to make contributions to GNSS and improving GNSS performance through international cooperation.
The high-level academic workshop will certainly deepen the mutual understanding between the Chinese and American experts in GNSS field. The China Satellite Navigation Office greatly supports the workshop and wishes for fruitful achievements.
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