3.7 Planning of TT&C Link
89
The telecommunication channel between Chang’E-3 lunar lander and the lunar
rover could be setup when required. Chang’E-3 lunar lander could receive and
transmit telemetry and scientific data of the lunar rover.
3.8 Design of Powered Descent and Soft Landing
The process of powered descent and soft landing was unique for the lunar lander.
The major tasks of this process could be summarized as following.
(1) To decelerate the velocity relative to the Moon to a certain range by lunar
lander’s propulsion system.
(2) To obtain height and velocity relative to lunar surface by onboard speedometer
and ranging sensors and IMU, and formulate control scheme autonomously by
onboard computer.
(3) To identify lunar terrain of landing site by onboard optical and laser sensors,
seeking safe landing site autonomously and formulate control scheme of
obstacle avoidance.
(4) To shut off main engine autonomously at certain height before lunar lander
touches lunar surface and ensure the falling velocity in a certain range.
(5) To absorb landing impact load by landing cushion mechanism, ensure stable
attitude after landing and support subsequent scientific exploration.
Different control schemes should be formulated according to different GNC control
scheme, configuration of navigation sensors and propulsion system.
3.8.1 Initial Status and Setup of Powered Descent
Generally, the start point of powered descent was design to be perilune of circumlunar
orbit. The altitude of perilune for Chang’E-3 lunar lander was designed to be 15 km.
The range of perilune altitude was determined by orbit control error, circumlunar
orbit perturbation and orbit determination error. The GNC subsystem should ensure
safe landing control within such range of initial status.
The setup before powered descent included folding of onboard mechanisms and
setup of initial parameters and sensor status.
The solar panel should be folded before powered descent to avoid damage to solar
panel by landing impact and power supply was provided by battery during powered
descent.
The initial orbit parameters, orbital calibration results of sensors, compensation and correction parameters and etc. were uplinked by ground station. There
was also uplink of delayed commands including power on of sensors, switch of
telecommunication channels and power on of descent camera in initial status setup.
89
The telecommunication channel between Chang’E-3 lunar lander and the lunar
rover could be setup when required. Chang’E-3 lunar lander could receive and
transmit telemetry and scientific data of the lunar rover.
3.8 Design of Powered Descent and Soft Landing
The process of powered descent and soft landing was unique for the lunar lander.
The major tasks of this process could be summarized as following.
(1) To decelerate the velocity relative to the Moon to a certain range by lunar
lander’s propulsion system.
(2) To obtain height and velocity relative to lunar surface by onboard speedometer
and ranging sensors and IMU, and formulate control scheme autonomously by
onboard computer.
(3) To identify lunar terrain of landing site by onboard optical and laser sensors,
seeking safe landing site autonomously and formulate control scheme of
obstacle avoidance.
(4) To shut off main engine autonomously at certain height before lunar lander
touches lunar surface and ensure the falling velocity in a certain range.
(5) To absorb landing impact load by landing cushion mechanism, ensure stable
attitude after landing and support subsequent scientific exploration.
Different control schemes should be formulated according to different GNC control
scheme, configuration of navigation sensors and propulsion system.
3.8.1 Initial Status and Setup of Powered Descent
Generally, the start point of powered descent was design to be perilune of circumlunar
orbit. The altitude of perilune for Chang’E-3 lunar lander was designed to be 15 km.
The range of perilune altitude was determined by orbit control error, circumlunar
orbit perturbation and orbit determination error. The GNC subsystem should ensure
safe landing control within such range of initial status.
The setup before powered descent included folding of onboard mechanisms and
setup of initial parameters and sensor status.
The solar panel should be folded before powered descent to avoid damage to solar
panel by landing impact and power supply was provided by battery during powered
descent.
The initial orbit parameters, orbital calibration results of sensors, compensation and correction parameters and etc. were uplinked by ground station. There
was also uplink of delayed commands including power on of sensors, switch of
telecommunication channels and power on of descent camera in initial status setup.