Introduction of BeiDou Navigation Satellite System
The introduction comprises the development process, component, working system, satellite navigation signals, service area and navigation parameters of the BeiDou Navigation Satellite System, in the hope of providing a comprehensive understanding about it.
I.Development Process
BeiDou Navigation Satellite System, with international registered name as COMPASS, is one of the four global navigation satellite systems.
Out of strong sense of political responsibility and the requirement of the times, while taking China’s national and military conditions into consideration, the constructors of BeiDou have creatively proposed the plan to build a dual satellite navigation system by using two geostationary satellites in the earth orbit and Digital Elevation Models.
To firstly meet the urgent need of satellite navigation under the system of active technique is the first step of China’s three-step strategy of navigation satellite system construction.
China’s independently developed navigation satellite system has completed its proof-of-principle and demonstration during 1985 to 1994.
From 1994 to 2002, BeiDou has entered a stage of experiment, research and construction. The BeiDou was officially put into operation in December, 2003, which made China the third country in the world capable of developing such a system on its own, and marked the opening to an age with BeiDou navigation satellite.
In 2004 the BeiDou Regional Navigation Satellite project was officially set up. By the end of 2012, 16 satellites have been sent into orbit, completing the construction of the BeiDou Regional Navigation Satellite System which is capable of providing passive services for the whole Asia-Pacific region.
The system, which consists of 3 geostationary orbit satellites and 27 non geostationary orbit satellites, is planned to offer global services upon its completion in 2020.
Pic.1 The development of BeiDou.
BeiDou is designed to be a backward compatible system so that its development is sustainable and it can keep upgrading. By constantly adding new satellites to its system, its function and the level of its general performance will be improved.
II.Component
BeiDou Navigation Satellite System is composed of three parts: the space section, the ground section and the user section.
Space Section
BeiDou navigation satellite will continuously send navigation message by radio wave to receiving end on earth so that the information can be applied to practical use.
Detailed launching time and types of BeiDou satellite are as in the picture below.
Pic.2 Launching of the BeiDou satellite.
Ground Section
In order to track and control the operation of BeiDou satellites, control station, injection station and monitor station are built on the ground. The main works of these ground stations are data collecting, navigation information computing, system monitoring, the correction and maintenance of each satellite’s parameter data and so forth.
User Section
The user section includes user terminals of BeiDou system and user terminals of other navigation satellite systems which are compatible with BeiDou. User section can track BeiDou satellites and figure out the coordinates, speed and time of the receiving end in real-time. The receiver can be classified into pocket-sized, backpack-sized, vehicle-mounted, shipborne, airborne and so on.
Pic.3 BeiDou User Section
III.Working System
BeiDou has officially begun its Radio Determination Satellite Service (RDSS) since 2002 and announced to offer Radio Navigation Satellite Service (RNSS) at the end of 2011.The two systems can be embedded in and reinforce each other, which can offer customers with continuous positioning services, velocity measuring services, location reports and short-message communication services.
Radio Determination Satellite Service (RDSS) can determine position of an object while providing location report and message communication. The measurement of distance between the user and satellite and location computing are conducted by the ground control station, by means of the reply of the user receiver.
Pic.4 The Three-Satellite-intersection principle of BeiDou.
In Radio Navigation Satellite System (RNSS), the user receiver receives radio wave navigation signals and independently conducts distance measurement of at least four satellites, so as to figure out the position, speed and navigation parameters of the user.
IV. Navigation Signals of Satellites
1. Carrier
BeiDou has three carrier waves whose frequencies are
B1------1561.098 MHZ
B2-------1207.140 MHZ
B3-------1268.520 MHZ
2. Pseudo Ranging Code
Ordinary Ranging Code: C Code
Precise Ranging Code: P Code
3. Data code
D code
V. Service Area
At the present, the service area of BeiDou covers most of the areas from 55°E to 180°E, 55°S to 55°N, and the priority area covers most of the areas from 70°E to 145°E,and from 5°N to 55°N.
The BeiDou signal covers an area west to the Persian Gulf and the Strait of Hormuz, east to the west of the Midway island, north to the city of Tynda in Russia, south to the south seas of Australia and New Zealand.
Pic.5 The service area of the BeiDou.
VI. Navigation Parameters
1. Coordinate System
BeiDou employs he CGCS2000 Coordinate Frames, whose parameters are as the picture below
Pic.6 Parameters of BeiDou.
2. Time System
BeiDou employs the BDT time system.
The epoch of BDT is 00:00 UTC on January1st, 2006.
3. Space System
The BeiDou employs China Geodetic Coordinate System 2000 (CGCS2000), whose precision is realized by means of the coordinates and speed of more than 2500 coordinates points of the GPD geodetic network 2000.
Coordinate: centimeter scale; Accuracy of Speed: mm/yr scale
4. Functional Parameter
BeiDou offers global customers with open, stable and reliable positioning services, including real-time navigation services, precise velocity and timing services, location report and SMS services with positioning accuracy of 10 meters, velocity accuracy of 0.2 meters / second and timing accuracy of 10 nanoseconds.