7.4 Design Methodology
231
Table 7.2 (continued)
Operation
modes
Attitude
determination
(Sensors)
Attitude
control
(actuators)
Orbit control
Phase
Slow
descending
Slow descending
during powered
descent
Rate damping
Gyro prediction
(gyros)
Phase plane
(10 N
thrusters)
/
Failure recovery
during orbit control
Non-control
Gyro prediction
(gyros)
/
/
Fault
medium) generated by propellant at a high speed to generate reaction thrust, which
is also called mass ejection actuator. The electromechanical actuator is generally
composed of a drive circuit, a motor, bearing, transmission, and rotational inertia,
such as inertial flywheel, control moment gyro for attitude control of space station,
de-spinning component for dual-spinning spacecraft, directional drive assembly for
solar panel, gimbal drive assembly for antenna pointing control, and etc. The environmental actuator uses the devices that generate moments through the interaction
between space environment and the spacecraft, such as magnetic torque, gravity
gradient rod, solar radiation pressure adjustment wing, and aerodynamic torque wing,
and etc.
According to requirements of the lunar lander mission, there were following
components in the GNC subsystem of the Chang’E-3 lunar lander.
1. Sun Sensor
The cruising attitude (sun orientation attitude) was maintained to ensure the power
supply of the lunar lander in most time of LTO and circumlunar orbit.
The Sun sensor was used to determine the direction of the Sun in the body coordinate system of the lunar lander and send solar orientation information to the Central
Control Unit for sun capture and orientation control, which was a key component of
the lunar lander during LTO and circumlunar orbit phases. It consisted of two parts:
sensor head and sensor circuit. The sensor head was used to sensitize Sun light and
convert it into electrical signals such as digital sun sensor and analog sun sensor.
The sensor circuit (integrated in the Image Processing Board of the Central Control
Unit) could process the signal output from the head to obtain the information about
the sun orientation and send it to the control computer.
The Sun sensor circuits were integrated into the Image Processing Board of the
Central Control Unit and there was a cold backup of Image Processing Board. The
output information of the Sun sensor was collected by its circuits and transferred to
the control computer through the internal serial port of the Central Control Unit. The
block diagram of the Sun sensor is shown in Fig. 7.2.
231
Table 7.2 (continued)
Operation
modes
Attitude
determination
(Sensors)
Attitude
control
(actuators)
Orbit control
Phase
Slow
descending
Slow descending
during powered
descent
Rate damping
Gyro prediction
(gyros)
Phase plane
(10 N
thrusters)
/
Failure recovery
during orbit control
Non-control
Gyro prediction
(gyros)
/
/
Fault
medium) generated by propellant at a high speed to generate reaction thrust, which
is also called mass ejection actuator. The electromechanical actuator is generally
composed of a drive circuit, a motor, bearing, transmission, and rotational inertia,
such as inertial flywheel, control moment gyro for attitude control of space station,
de-spinning component for dual-spinning spacecraft, directional drive assembly for
solar panel, gimbal drive assembly for antenna pointing control, and etc. The environmental actuator uses the devices that generate moments through the interaction
between space environment and the spacecraft, such as magnetic torque, gravity
gradient rod, solar radiation pressure adjustment wing, and aerodynamic torque wing,
and etc.
According to requirements of the lunar lander mission, there were following
components in the GNC subsystem of the Chang’E-3 lunar lander.
1. Sun Sensor
The cruising attitude (sun orientation attitude) was maintained to ensure the power
supply of the lunar lander in most time of LTO and circumlunar orbit.
The Sun sensor was used to determine the direction of the Sun in the body coordinate system of the lunar lander and send solar orientation information to the Central
Control Unit for sun capture and orientation control, which was a key component of
the lunar lander during LTO and circumlunar orbit phases. It consisted of two parts:
sensor head and sensor circuit. The sensor head was used to sensitize Sun light and
convert it into electrical signals such as digital sun sensor and analog sun sensor.
The sensor circuit (integrated in the Image Processing Board of the Central Control
Unit) could process the signal output from the head to obtain the information about
the sun orientation and send it to the control computer.
The Sun sensor circuits were integrated into the Image Processing Board of the
Central Control Unit and there was a cold backup of Image Processing Board. The
output information of the Sun sensor was collected by its circuits and transferred to
the control computer through the internal serial port of the Central Control Unit. The
block diagram of the Sun sensor is shown in Fig. 7.2.