7.4 Design Methodology
233
The MRVS was used to measure the distance and velocity of the lunar lander relative
to lunar surface so as to correct the navigation results of the IMUs. The MRVS
consisted of two types of sensors: range sensors and velocity sensors, wherein the
range sensor used pulsed wave Doppler at long distance and uses quasi-continuous
wave for close range with separate receiving and transmitting antennas. The velocity
sensors used continuous wave with separate transmitting and receiving antennas were
standalone. The MRVS consisted of antennas, velocity measurement diaphragms,
transmitting/receiving channels, signal process unit, frequency synthesizer, crystal
oscillators, power distribution controller, and matching waveguides and cables.
The 10 antennas of the MRVS formed 5 measuring beams (a receiving antenna
and a transmitting antenna for each beam): R1 (T1), R2 (T2) and R3 (T3) were three
standalone velocity measuring beams, R4 (T4) was a long-distance ranging beam,
and R5 (T5) was a short-range ranging beam. The transmitting/receiving channels
included ranging transmitting/receiving channels and velocity transmitting/receiving
channels (three velocity measurement beams shared the transmitting channel, but
the receiving channel was mutually independent). The signal process unit included a
range DSP, a primary velocity DSP, and their backup. The crystal oscillator, frequency
synthesizer and power distribution controller were backed up, in which the crystal
oscillator was hot backup, frequency synthesizer and power distribution controller
were cold backup. In addition, three waveguide switches were configured to complete
the primary-backup switching for speed measurement and beam switching for long
and close range measurement.
Configuration of the MRVS is shown in Fig. 7.3.
5. Laser Rangefinder
The Laser Rangefinder was used to measure the distance between the lunar lander
and lunar surface. The Laser Rangefinder used the pulsed laser to measure the
distance. It adopted an integrated design and had two orthogonal directions to meet
the requirements for long distance and near distance ranging respectively.
The block diagram of the Laser Rangefinder is shown in Fig. 7.4. The laser unit
was an active Q-switched high-power laser. From a color separation sheet on a beam
expander of the laser unit, the beam was divided into two orthogonal directions of
–Z axis direction and –X axis direction.
The Laser Rangefinder consisted of laser and laser drive unit, laser receiving unit,
signal process unit, secondary power unit and thermal control unit.
6. 3-D Laser Image Sensor
Because the scientifically valuable areas are usually cliffs or craters, where the obstacles are widely distributed and lunar terrain is complex. Therefore, in order to ensure
that the lunar lander was landed accurately in a safe area, it was necessary to configure
imaging sensors to image the lunar surface in order to achieve hazard avoidance and
ensure landing safety. The 3-D Laser Image Sensor was one of the landing navigation
sensors for 3-D imaging of the landing area when the distance was about 100 meters
above lunar surface. The obtained 3-D elevation map data of lunar surface was used
for hazard detection and obstacle avoidance.
233
The MRVS was used to measure the distance and velocity of the lunar lander relative
to lunar surface so as to correct the navigation results of the IMUs. The MRVS
consisted of two types of sensors: range sensors and velocity sensors, wherein the
range sensor used pulsed wave Doppler at long distance and uses quasi-continuous
wave for close range with separate receiving and transmitting antennas. The velocity
sensors used continuous wave with separate transmitting and receiving antennas were
standalone. The MRVS consisted of antennas, velocity measurement diaphragms,
transmitting/receiving channels, signal process unit, frequency synthesizer, crystal
oscillators, power distribution controller, and matching waveguides and cables.
The 10 antennas of the MRVS formed 5 measuring beams (a receiving antenna
and a transmitting antenna for each beam): R1 (T1), R2 (T2) and R3 (T3) were three
standalone velocity measuring beams, R4 (T4) was a long-distance ranging beam,
and R5 (T5) was a short-range ranging beam. The transmitting/receiving channels
included ranging transmitting/receiving channels and velocity transmitting/receiving
channels (three velocity measurement beams shared the transmitting channel, but
the receiving channel was mutually independent). The signal process unit included a
range DSP, a primary velocity DSP, and their backup. The crystal oscillator, frequency
synthesizer and power distribution controller were backed up, in which the crystal
oscillator was hot backup, frequency synthesizer and power distribution controller
were cold backup. In addition, three waveguide switches were configured to complete
the primary-backup switching for speed measurement and beam switching for long
and close range measurement.
Configuration of the MRVS is shown in Fig. 7.3.
5. Laser Rangefinder
The Laser Rangefinder was used to measure the distance between the lunar lander
and lunar surface. The Laser Rangefinder used the pulsed laser to measure the
distance. It adopted an integrated design and had two orthogonal directions to meet
the requirements for long distance and near distance ranging respectively.
The block diagram of the Laser Rangefinder is shown in Fig. 7.4. The laser unit
was an active Q-switched high-power laser. From a color separation sheet on a beam
expander of the laser unit, the beam was divided into two orthogonal directions of
–Z axis direction and –X axis direction.
The Laser Rangefinder consisted of laser and laser drive unit, laser receiving unit,
signal process unit, secondary power unit and thermal control unit.
6. 3-D Laser Image Sensor
Because the scientifically valuable areas are usually cliffs or craters, where the obstacles are widely distributed and lunar terrain is complex. Therefore, in order to ensure
that the lunar lander was landed accurately in a safe area, it was necessary to configure
imaging sensors to image the lunar surface in order to achieve hazard avoidance and
ensure landing safety. The 3-D Laser Image Sensor was one of the landing navigation
sensors for 3-D imaging of the landing area when the distance was about 100 meters
above lunar surface. The obtained 3-D elevation map data of lunar surface was used
for hazard detection and obstacle avoidance.