438
13 Metrology Technology of Lunar Lander
parameters, the measurement accuracy in dynamic loading process should achieve
the same accuracy as the static measurement, which was very difficult.
In summary, because of mission characteristics of the lunar Lander, many new
measurement methods and technologies were applied in metrology. In the alignment measurement, there were applications including the normal direction measurement of the ranging and speedometer antenna end surface based on common point
transformation and three-dimensional shape scanning measurement of the interface
ring based on Unified Space Metrology Network (USMN), which solved the issue
of measurement data fusion and high accuracy requirements under complex conditions. The automatic leak test technology and quick leak positioning technology were
applied in system leak test of propulsion subsystem, which effectively improved the
accuracy, reliability and safety. In the measurement of mass property, technologies
were applied including mass property test technology based on multi freedom transformation, test and correction technology during propellant loading, and center of
gravity correction technology with ballast, so as to acquire inertia of the lunar lander
with high accuracy and efficiency.
13.4 Application of Special Measurement Technology
13.4.1 Normal Direction Measurement of Ranging
and Speedometer Antenna End-Surface Based
on Common Point Transformation
1. Requirements
According to autonomous control of the Chang’E-3 lunar lander during soft-landing,
the alignment of the Range and Velocity Sensor (RVS) antennas should be measured
in system assembly phase of the Chang’E-3 lunar lander and the measurement accuracy should be better than 2
. There were several ranging and speedometer antennas
with different pointing direction on the lunar lander. At same time, because it was
impossible to install reference mirror on the antenna and its support to the structure design of the antenna, the optical cube reference cannot be installed on the
antenna and its supporter, the conventional theodolite measurement could not be
implemented. Therefore, an integrated measurement method with laser track and
theodolite were applied to measure the points’ coordinates of the circular antenna
ring and determine the direction of electrical axis of the antenna, as shown in Fig. 13.1.
2. Technical Design and Principle
When the lunar lander was assembled, the position and attitude of instruments
onboard was established to the reference coordinate system O 1 -X 1 Y 1 Z 1 based on 3
pin holes center I, II and III on the interface between the lunar lander and the launch
vehicle, as shown in Fig. 13.2. However, in assembly process, the 3 pin holes between
13 Metrology Technology of Lunar Lander
parameters, the measurement accuracy in dynamic loading process should achieve
the same accuracy as the static measurement, which was very difficult.
In summary, because of mission characteristics of the lunar Lander, many new
measurement methods and technologies were applied in metrology. In the alignment measurement, there were applications including the normal direction measurement of the ranging and speedometer antenna end surface based on common point
transformation and three-dimensional shape scanning measurement of the interface
ring based on Unified Space Metrology Network (USMN), which solved the issue
of measurement data fusion and high accuracy requirements under complex conditions. The automatic leak test technology and quick leak positioning technology were
applied in system leak test of propulsion subsystem, which effectively improved the
accuracy, reliability and safety. In the measurement of mass property, technologies
were applied including mass property test technology based on multi freedom transformation, test and correction technology during propellant loading, and center of
gravity correction technology with ballast, so as to acquire inertia of the lunar lander
with high accuracy and efficiency.
13.4 Application of Special Measurement Technology
13.4.1 Normal Direction Measurement of Ranging
and Speedometer Antenna End-Surface Based
on Common Point Transformation
1. Requirements
According to autonomous control of the Chang’E-3 lunar lander during soft-landing,
the alignment of the Range and Velocity Sensor (RVS) antennas should be measured
in system assembly phase of the Chang’E-3 lunar lander and the measurement accuracy should be better than 2
. There were several ranging and speedometer antennas
with different pointing direction on the lunar lander. At same time, because it was
impossible to install reference mirror on the antenna and its support to the structure design of the antenna, the optical cube reference cannot be installed on the
antenna and its supporter, the conventional theodolite measurement could not be
implemented. Therefore, an integrated measurement method with laser track and
theodolite were applied to measure the points’ coordinates of the circular antenna
ring and determine the direction of electrical axis of the antenna, as shown in Fig. 13.1.
2. Technical Design and Principle
When the lunar lander was assembled, the position and attitude of instruments
onboard was established to the reference coordinate system O 1 -X 1 Y 1 Z 1 based on 3
pin holes center I, II and III on the interface between the lunar lander and the launch
vehicle, as shown in Fig. 13.2. However, in assembly process, the 3 pin holes between