What aspects does the China Big Dipper system specifically include?

Beidou navigation and positioning system (Beidou system for short) consists of three parts: space constellation, ground control center system and user terminal.

1, space constellation

The space segment of China Beidou Navigation System (COMPASS) under construction is planned to consist of 5 geostationary satellites and 30 non-geostationary satellites, providing two service modes: open service and authorized service. It is 36000km away from the ground and located above the equator of 80 and140 respectively, and performs the relay task of two-way radio signals between the ground control center and the user terminal. There is also a backup satellite located above the equator at east longitude 1 15.5. The satellite weighs 980kg and its service life is not less than 8 years.

2. Ground control center system

The ground control center of Beidou system includes main control, orbit measuring station, altitude measuring station, correction station and calculation center, which is mainly used for measuring and collecting corrected navigation and positioning parameters, completing orbit measuring and adjusting satellite orbit and attitude, compiling ephemeris, forming user positioning correction data and positioning users, that is, receiving and sending radio signals and monitoring and managing the whole working system.

3. User equipment

There are usually five types of Beidou user machines according to their different application environments and functions:

Ordinary type.

This kind of user machine can only perform positioning and point-to-point communication, and is suitable for positioning and navigation applications of general cars, ships and portable users. It can receive and send positioning and communication information, and conduct two-way communication with the central station and other user terminals.

Communication type.

It is suitable for all kinds of data acquisition and data transmission users such as field work, hydrological measurement and environmental detection. , and can send and receive short messages and messages, and communicate with the central station and other user terminals in two-way or one-way manner.

Timing type.

It is suitable for users such as time service, time correction and time synchronization, and can provide time synchronization accuracy of tens of nanoseconds.

Command type.

The command user machine is used by the superior group management department with a certain number of users. In addition to all the functions of ordinary user computers, it can also broadcast broadcast information and receive positioning communication information sent by the central control system to its users. The command user machine can be divided into one, two and three levels. Among them, the first-level command user machine, and the users under its jurisdiction are ordinary user machines; Secondary command user machine, and the users under its jurisdiction are primary command user machines; Three-level command user machine, the users under its jurisdiction are two-level command machine users.

Multi-model user machine.

The user machine can not only receive Beidou satellite positioning and communication information, but also use GPS system or GPS enhanced system for navigation and positioning, which is suitable for users with high requirements for location information.