BeiDou Navigation Satellite System Signal In Space Interface Control Document

木文一刀

BeiDou Navigation Satellite System Signal In Space Interface Control Document (Test Version)
China Satellite Navigation Office
December 2011
1 Scope
The BeiDou Navigation Satellite System (hereinafter referred to
as BeiDou system) has followed the development roadmap of
starting with regional services first and expanding to global services
later. A three-step development strategy has been 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.
This interface document defines the specification related to B1
carrier signal between the space segment and the user segment of the
BeiDou Navigation Satellite (regional) System.
2 System Overview
2.1 Space Constellation
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.
2.2 Coordinate System
The BeiDou system adopts the China Geodetic Coordinate
System 2000 (CGCS2000), the definition of which is listed below:
The origin is located at the mass center of the Earth;
The Z-axis is in the direction of the IERS (International Earth
Rotation Service) Reference Pole (IRP);
The X-axis is directed to the intersection of IERS Reference
Meridian (IRM) and the plane passing through the origin and normal
to the Z-axis;
The Y-axis, together with Z-axis and X-axis, constitutes a right
handed orthogonal coordinate system.
The origin of the CGCS2000 is also the geometric center of the
CGCS2000 ellipsoid, and the Z-axis is the rotation axis of the
CGCS2000 ellipsoid. The parameters of the CGCS2000 ellipsoid are
as follows:
Semi-major axis: a = 6378137.0 m
Geocentric gravitational constant (mass of the earth atmosphere
included): GM = 398600.4418´109 m3/s2
Flattening: f = 1/298.257222101
Rate of earth rotation: w = 7.2921150´10-5 rad/s
2.3 Time System
The BeiDou Time (BDT) System is a continuous timekeeping
system, with its length of second being a SI second. BDT zero
time-point started at 00:00 UTC on January 1st, 2006. BDT is
synchronized with UTC in 100 nanoseconds (modulo one second).
3 B1 Signal Specifications
3.1 Signal Structure and Basic Characteristics
3.1.1 Signal Structure
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.
The B1 signal is expressed as follows:
j j ( ) j ( )cos (2 j ) j ( ) j ( )sin (2 j )
C C C P P P S = A C t D t p ft +j + A P t D t p ft +j
Where,
j: Satellite number
A : Amplitude of ranging code in channel I of carrier B1
P A : Amplitude of ranging code in channel Q of carrier B1
C : Ranging code in channel I
P : Ranging code in channel Q
C D : Data modulated on ranging code of channel I
P D : Data modulated on ranging code of channel Q
f : B1 carrier frequency
C j : Initial phase of channel I of carrier B1
P j : Initial phase of channel Q of carrier B1
3.1.2 Basic Signal Characteristics
The basic characteristics and parameters of B1 signals are
shown in Table 3-1.