4.6 Navigation Satellite System
241
The FOC Galileo satellites transmit 10 right-hand circularly polarized navigation
signals and 1 search and rescue signal, where the navigation signals are broadcasted, respectively, in three carrier frequency bands, namely, 1164−1215 MHz,
1260−1300 MHz and 1559−1591 MHz, and the search and rescue signal is broadcasted in the reserved frequency band of emergency service, 1544−1545 MHz. When
the Galileo constellation provides global continuous signal coverage, the ground user
receiver can track up to 13 satellites at the same time. The Galileo system affords five
types of basic services: Open Service (OS), Commercial Service (CS), Safety-of-Life
(SoL), Public Regulated Service (PRS), and Search and Rescue (SAR) [14].
The OS is to provide free positioning, speed measurement and time service information to global users, with the horizontal positioning accuracy of 4 m (2-sigma) and
the vertical accuracy of 8 m (2-sigma) for dual-frequency receivers, the timing accuracy of 30 ns (2-sigma) for the triple frequency receivers and the service availability
of 99.5%, but the OS users cannot get the integrity information from the Galileo
system, and their safeties using the Galileo system are not protected. The CS, which
provides the development for professional application, can broadcast commercial
encrypted information with high data rate, and obtains high-precision positioning
and good system performance service, and its foreseeable applications are to the
fields such as wireless communication network integration and indoor navigation.
The SoL is with a navigation availability of 99.8% to ensure the safety of life, and
its applications are to the fields endangering users’ life and safety, such as land
vehicles, sea voyage and aviation, which require rapid, timely and comprehensive
system integrity information as well as high-level positioning, navigation and timing
services. The PRS is to use the special frequency bands and signals to encrypt data
information, and is able to get all information of the Galileo system, protecting the
space signals of the Galileo system from being destroyed. The PRS is managed and
controlled by specialized agency approved by the EU. The Galileo satellites carry the
SAR payloads. Once distress alerting information is detected, it will be transmitted
to the ground SAR center through the special frequency band to provide the disaster
location and relevant information, so as to take rescue measures in time.
4.7 The Navigations for Spacecrafts
It is well known that the motion states of a spacecraft can be expressed by the
position and velocity parameters of its center of mass, as well as the parameters of
the rotational angles and their rates, in which the spacecraft rotates around its center of
mass. The position and velocity parameters are used to express the moving trajectory
of the spacecraft, commonly known as orbital parameters, and the rotational angle
and its rates are used to express the spatial orientation of the spacecraft, commonly
known as attitude parameters. That is to say, the spacecraft, regarded as a rigid
body moving, has six Degrees of Freedom (DOF), three of which represent its orbital
motion states, and the other three represent its attitude motion states. The spacecraft
moving in space is always affected by various forces and moments, in which the
241
The FOC Galileo satellites transmit 10 right-hand circularly polarized navigation
signals and 1 search and rescue signal, where the navigation signals are broadcasted, respectively, in three carrier frequency bands, namely, 1164−1215 MHz,
1260−1300 MHz and 1559−1591 MHz, and the search and rescue signal is broadcasted in the reserved frequency band of emergency service, 1544−1545 MHz. When
the Galileo constellation provides global continuous signal coverage, the ground user
receiver can track up to 13 satellites at the same time. The Galileo system affords five
types of basic services: Open Service (OS), Commercial Service (CS), Safety-of-Life
(SoL), Public Regulated Service (PRS), and Search and Rescue (SAR) [14].
The OS is to provide free positioning, speed measurement and time service information to global users, with the horizontal positioning accuracy of 4 m (2-sigma) and
the vertical accuracy of 8 m (2-sigma) for dual-frequency receivers, the timing accuracy of 30 ns (2-sigma) for the triple frequency receivers and the service availability
of 99.5%, but the OS users cannot get the integrity information from the Galileo
system, and their safeties using the Galileo system are not protected. The CS, which
provides the development for professional application, can broadcast commercial
encrypted information with high data rate, and obtains high-precision positioning
and good system performance service, and its foreseeable applications are to the
fields such as wireless communication network integration and indoor navigation.
The SoL is with a navigation availability of 99.8% to ensure the safety of life, and
its applications are to the fields endangering users’ life and safety, such as land
vehicles, sea voyage and aviation, which require rapid, timely and comprehensive
system integrity information as well as high-level positioning, navigation and timing
services. The PRS is to use the special frequency bands and signals to encrypt data
information, and is able to get all information of the Galileo system, protecting the
space signals of the Galileo system from being destroyed. The PRS is managed and
controlled by specialized agency approved by the EU. The Galileo satellites carry the
SAR payloads. Once distress alerting information is detected, it will be transmitted
to the ground SAR center through the special frequency band to provide the disaster
location and relevant information, so as to take rescue measures in time.
4.7 The Navigations for Spacecrafts
It is well known that the motion states of a spacecraft can be expressed by the
position and velocity parameters of its center of mass, as well as the parameters of
the rotational angles and their rates, in which the spacecraft rotates around its center of
mass. The position and velocity parameters are used to express the moving trajectory
of the spacecraft, commonly known as orbital parameters, and the rotational angle
and its rates are used to express the spatial orientation of the spacecraft, commonly
known as attitude parameters. That is to say, the spacecraft, regarded as a rigid
body moving, has six Degrees of Freedom (DOF), three of which represent its orbital
motion states, and the other three represent its attitude motion states. The spacecraft
moving in space is always affected by various forces and moments, in which the