Chapter 7
Guidance, Navigation and Control
Technology of Lunar Lander
7.1 Introduction
Guidance, Navigation, and Control (GNC) subsystem was one of key subsystems for
the lunar lander [1]. Major functions of GNC subsystem were: trajectory corrections
maneuvers during LTO, LOI at perilune, orbit phase adjustment and de-orbit burn,
soft-landing GNC during powered descent.
Compared with GNC subsystem of conventional spacecraft, the main challenge
for GNC subsystem of the lunar lander was the powered descent phase, which was
also the key and the most difficult process of lunar soft-landing mission. Due to short
duration of the powered descent phase, large velocity change and uncertainty of lunar
terrain, it was impossible to depend on ground control. Therefore, it was necessary
to design a fully autonomous landing control strategy based on range measurement
and terrain recognition.
The guidance system autonomously generated commands for the main engine
(including magnitude and direction) based on task and the lander status given by
the navigation system. The navigation system determined the lunar lander status
(including orbit and attitude information) based on the information given by relative navigation sensors and Inertial Measurement Units (IMUs). The control system
implemented the desired attitude tracking or attitude maneuver through the actuators
according to the current attitude determined by the navigation system and the target
attitude given by the guidance system [2, 3].
The major technologies of GNC subsystem of the lunar lander are described in
this chapter, including the general architecture design of the subsystem, hardware
and software design techniques, and typical methods of guidance, navigation, and
control, and etc.
© National Defense Industry Press and Springer Nature Singapore Pte Ltd. 2021
D.-Y. Yu et al., Technology of Lunar Soft Lander, Space Technology Library 38,
https://doi.org/10.1007/978-981-15-6580-9_7
225
Guidance, Navigation and Control
Technology of Lunar Lander
7.1 Introduction
Guidance, Navigation, and Control (GNC) subsystem was one of key subsystems for
the lunar lander [1]. Major functions of GNC subsystem were: trajectory corrections
maneuvers during LTO, LOI at perilune, orbit phase adjustment and de-orbit burn,
soft-landing GNC during powered descent.
Compared with GNC subsystem of conventional spacecraft, the main challenge
for GNC subsystem of the lunar lander was the powered descent phase, which was
also the key and the most difficult process of lunar soft-landing mission. Due to short
duration of the powered descent phase, large velocity change and uncertainty of lunar
terrain, it was impossible to depend on ground control. Therefore, it was necessary
to design a fully autonomous landing control strategy based on range measurement
and terrain recognition.
The guidance system autonomously generated commands for the main engine
(including magnitude and direction) based on task and the lander status given by
the navigation system. The navigation system determined the lunar lander status
(including orbit and attitude information) based on the information given by relative navigation sensors and Inertial Measurement Units (IMUs). The control system
implemented the desired attitude tracking or attitude maneuver through the actuators
according to the current attitude determined by the navigation system and the target
attitude given by the guidance system [2, 3].
The major technologies of GNC subsystem of the lunar lander are described in
this chapter, including the general architecture design of the subsystem, hardware
and software design techniques, and typical methods of guidance, navigation, and
control, and etc.
© National Defense Industry Press and Springer Nature Singapore Pte Ltd. 2021
D.-Y. Yu et al., Technology of Lunar Soft Lander, Space Technology Library 38,
https://doi.org/10.1007/978-981-15-6580-9_7
225