246
4 Navigations from Ground to Space
singular problem, the constraints are simple and the attitude kinematics equations
are linear. So, the quaternion method is usually used to determine the attitudes of
spacecrafts.
4.7.2 Orbit and Attitude Controls
Through the orbit determination, the spacecraft’s real-time navigation parameters
including position and velocity are obtained to determine whether the spacecraft
deviates from the expected orbits. The orbit control for the spacecraft refers to the
process of applying external force to the spacecraft’s center of mass, purposefully
changing its trajectory, making it return to the expected orbits or fly to the target celestial bodies. According to the different practical applications, the spacecraft’s orbit
controls can generally be divided into four categories. One is the orbit maneuver, a
control process that the spacecrafts are transferred from one free-flight orbit segment
to another. For example, when the geostationary orbit satellite is launched, the orbit
maneuver will be carried out at the apogee where the orbit is transferred. The other
is the orbit keeping, a control process of overcoming the orbit perturbation to keep
some orbital parameters unchanged for the spacecrafts, such as the station keeping
for the GEO satellites, the formation keeping for navigation constellations, the orbital
inclination keeping for the Sun synchronous orbit satellites and the repeated period
keeping for the orbit-repeated satellites. The third is the orbit rendezvous, a control
process that two spacecrafts reach the same position in space at the same time and
at the same speed, such as the rendezvous and docking between spaceship and space
station, etc. The fourth is the re-entry, a control process that the spacecraft leaves
its original flight orbit and returns to the Earth’s atmosphere, such as the re-entry for
the spaceship back to the ground, etc.
Through the autonomous attitude determination, the spacecraft’s real-time attitude
parameters are obtained to determine whether their errors are within a tolerance
range. The attitude control for the spacecraft refers to the process of applying
the moment of a force to the spacecraft around the center of mass to maintain or
change its spatial orientation, including attitude stabilization and attitude maneuver.
The attitude stabilization refers to the control process of keeping the attitudes of
spacecrafts in the specified direction, which requires the control system to work
continuously during the lifetime of the spacecrafts, with the long-term and frequent
characteristics and the small control moments required. The attitude maneuver
refers to the reorientation process of the spacecraft from one attitude to another,
which generally lasts for a short time and uses a great control moment to make the
spacecraft’s attitude change obviously. According to the different motion ways of
spacecrafts, the attitude stabilization can be roughly classified into two categories:
one is the spin stabilization, a control process that the spacecraft rotates about the
spin axis and maintains the inertial spatial direction of the spin axis by using the
spinning momentum torque; the other is the three-axis stabilization, the control
process of keeping the three orthogonal axes of the spacecraft in a certain reference
4 Navigations from Ground to Space
singular problem, the constraints are simple and the attitude kinematics equations
are linear. So, the quaternion method is usually used to determine the attitudes of
spacecrafts.
4.7.2 Orbit and Attitude Controls
Through the orbit determination, the spacecraft’s real-time navigation parameters
including position and velocity are obtained to determine whether the spacecraft
deviates from the expected orbits. The orbit control for the spacecraft refers to the
process of applying external force to the spacecraft’s center of mass, purposefully
changing its trajectory, making it return to the expected orbits or fly to the target celestial bodies. According to the different practical applications, the spacecraft’s orbit
controls can generally be divided into four categories. One is the orbit maneuver, a
control process that the spacecrafts are transferred from one free-flight orbit segment
to another. For example, when the geostationary orbit satellite is launched, the orbit
maneuver will be carried out at the apogee where the orbit is transferred. The other
is the orbit keeping, a control process of overcoming the orbit perturbation to keep
some orbital parameters unchanged for the spacecrafts, such as the station keeping
for the GEO satellites, the formation keeping for navigation constellations, the orbital
inclination keeping for the Sun synchronous orbit satellites and the repeated period
keeping for the orbit-repeated satellites. The third is the orbit rendezvous, a control
process that two spacecrafts reach the same position in space at the same time and
at the same speed, such as the rendezvous and docking between spaceship and space
station, etc. The fourth is the re-entry, a control process that the spacecraft leaves
its original flight orbit and returns to the Earth’s atmosphere, such as the re-entry for
the spaceship back to the ground, etc.
Through the autonomous attitude determination, the spacecraft’s real-time attitude
parameters are obtained to determine whether their errors are within a tolerance
range. The attitude control for the spacecraft refers to the process of applying
the moment of a force to the spacecraft around the center of mass to maintain or
change its spatial orientation, including attitude stabilization and attitude maneuver.
The attitude stabilization refers to the control process of keeping the attitudes of
spacecrafts in the specified direction, which requires the control system to work
continuously during the lifetime of the spacecrafts, with the long-term and frequent
characteristics and the small control moments required. The attitude maneuver
refers to the reorientation process of the spacecraft from one attitude to another,
which generally lasts for a short time and uses a great control moment to make the
spacecraft’s attitude change obviously. According to the different motion ways of
spacecrafts, the attitude stabilization can be roughly classified into two categories:
one is the spin stabilization, a control process that the spacecraft rotates about the
spin axis and maintains the inertial spatial direction of the spin axis by using the
spinning momentum torque; the other is the three-axis stabilization, the control
process of keeping the three orthogonal axes of the spacecraft in a certain reference