BEIDOU GLOBAL NAVIGATION SATELLITE SYSTEM
The concept for a Chinese Regional Navigation System was first introduced in 1983. In 1989, the system using two geostationary DFH-2/2A communication satellites (code name: Twinsat) passed in-orbit validation. The first dedicated satellite, BeiDou-1A was launched on 30 October 2000, followed by BeiDou-1B on 20 December 2000. The third satellite, BeiDou-1C was put into orbit on 25 May 2003 as a backup.
The BeiDou-1 (BeiDou – "Northern Dipper" – the Chinese for the Big Dipper constellation) satellites were constructed based on DFH-3 geostationary communication platform. On 15 December 2003 the first generation BeiDou system was successfully put into operation that made China one of the three countries owning their navigation satellite systems.
In 2006, China officially announced the development of the national second generation GNSS including constellation of MEO satellites – BeiDou-2 (or Compass as an alternative name).
BeiDou will deliver two types of global and two types of regional services. Global services are open and authorized services. Regional services are wide area differential and short message services.
By 2020, the BeiDou orbital constellation will include 35 satellites:
TYPES OF SATELLITES
NAVIGATION RADIO SIGNALS
BeiDou transmits navigation signals in three frequency bands: B1, B2, and B3, which are in the same area of L-band as other GNSS signals.
To benefit from the signal interoperability of BeiDou with Galileo and GPS China announced the migration of its civil B1 signal from 1561.098 MHz to a frequency centered at 1575.42 MHz — the same as the GPS L1 and Galileo E1 civil signals — and its transformation from a quadrature phase shift keying (QPSK) modulation to a multiplexed binary offset carrier (MBOC) modulation similar to the future GPS L1C and Galileo’s E1.
GEODETIC REFERENCE SYTEM AND TIME SCALE
BeiDou satellites motion parameters are transmitted in CGCS2000 (the China Geodetic Coordinate System 2000). Its origin is the center of mass of the whole Earth. Its Z-axis directs from the origin to the reference pole of the International Earth Rotation Service (IERS Reference Pole). Its X-axis directs from the origin to the intersection between IERS Reference meridian and the plane perpendicular to Z-axis. Its Y-axis completes a right-handed, Earth-Centered Earth-Fixed (ECEF) orthogonal coordinate system.
The Chinese Universal Global Time is defined as a BeiDou system timescale based on the atomic frequency standard set maintained in the System Control Center in Bejing. BeiDou System Time (BDT) is a continuous time scale steered to UTC reference with 100 ns offset. BDT origin is 0:00 of January 1st, 2006. BDT-GPS and BDT-GST offsets are being measured and broadcast. BDT-GLONASS Time offset broadcast is also anticipated.
GROUND CONTROL SEGMENT
The BeiDou Ground Control Segment is based on a classic centralized scheme including the network of one-way measuring stations which monitor the navigation signals of all satellites on a continuous basis and transmit all the observations of all satellites for processing to the system control center which generates the precise orbit and clock data for each satellite to be uploaded to satellites via up-link stations.
The network of one-way stations is located throughout China. The long-term strategy of system development suggests that a global network of stations should be deployed to increase the BeiDou performance.
INTERFACE CONTROL DOCUMENT
BeiDou Interface Control Document:
BeiDou User Information Center: en.beidou.gov.cnНаверх