10.3 Analysis of Technical Characteristics
339
the lunar lander in any gesture could be ensured. Because of shielding of the lunar
lander body to the antenna, two pairs of omnidirectional antennas to cover each half
space should be configured. Two antennas were installed symmetrically to cover the
full space.
10.3.2 Mission Characteristics
There were characteristics including long distance, complex channel model and operation mode for lunar soft-landing mission compared with Earth orbit spacecraft
mission.
1. Long Distance
Compared with Earth orbit spacecraft, the telecommunication path loss in the deep
space missions is higher because the telecommunication distance becomes further.
One of technical challenges in deep space missions is to make up for such loss to
achieve telemetry/telecommand and telecommunication [9]. The farthest telecommunication distance and telecommunication delay of the lunar probe are shown in
Table 10.1.
Compared with Earth orbit spacecraft, if same ground station with same configuration was applied for lunar landing missions, it was necessary to enhance the receiving
and transmitting capability of the lunar lander by about 20 dB to implement same
telemetry/telecommand and telecommunication. In order to reduce the requirements
for the lunar lander, more powerful deep space network should be built up. There was
large aperture antenna, high-power transmitter and high sensitivity receiving system
for deep space network compared with common ground station.
2. Complex Channel Model
Besides the telemetry/telecommand and telecommunication channel between the
lunar lander and the ground station, there might be telecommunication channel among
lunar probes on lunar surface in lunar missions. The telecommunication channel
model of lunar probes was more complex than probe-ground link.
The propagation media of telecommunication on lunar surface was different from
that of the probe-ground telecommunication. In the probe-ground telecommunication, radio waves could be seen as straight line propagation, and the propagation
media are vacuum environment and earth atmosphere. In vacuum environment, the
quality of telecommunication system is affected by free space loss and additive
Gauss white noise. When the radio wave enters Earth atmosphere, it is necessary
to consider the attenuation of precipitation, vapor in atmosphere and oxygen. In
telecommunication on lunar surface, the propagation media is extremely tenuous
Table 10.1 Farthest telecommunication distance and telecommunication delay of lunar probe [9]
Farthest distance/km
Increased path loss (to geostationary orbit spacecraft)/dB
Delay/s
0.4055 × 10 6
21.03
1.35
339
the lunar lander in any gesture could be ensured. Because of shielding of the lunar
lander body to the antenna, two pairs of omnidirectional antennas to cover each half
space should be configured. Two antennas were installed symmetrically to cover the
full space.
10.3.2 Mission Characteristics
There were characteristics including long distance, complex channel model and operation mode for lunar soft-landing mission compared with Earth orbit spacecraft
mission.
1. Long Distance
Compared with Earth orbit spacecraft, the telecommunication path loss in the deep
space missions is higher because the telecommunication distance becomes further.
One of technical challenges in deep space missions is to make up for such loss to
achieve telemetry/telecommand and telecommunication [9]. The farthest telecommunication distance and telecommunication delay of the lunar probe are shown in
Table 10.1.
Compared with Earth orbit spacecraft, if same ground station with same configuration was applied for lunar landing missions, it was necessary to enhance the receiving
and transmitting capability of the lunar lander by about 20 dB to implement same
telemetry/telecommand and telecommunication. In order to reduce the requirements
for the lunar lander, more powerful deep space network should be built up. There was
large aperture antenna, high-power transmitter and high sensitivity receiving system
for deep space network compared with common ground station.
2. Complex Channel Model
Besides the telemetry/telecommand and telecommunication channel between the
lunar lander and the ground station, there might be telecommunication channel among
lunar probes on lunar surface in lunar missions. The telecommunication channel
model of lunar probes was more complex than probe-ground link.
The propagation media of telecommunication on lunar surface was different from
that of the probe-ground telecommunication. In the probe-ground telecommunication, radio waves could be seen as straight line propagation, and the propagation
media are vacuum environment and earth atmosphere. In vacuum environment, the
quality of telecommunication system is affected by free space loss and additive
Gauss white noise. When the radio wave enters Earth atmosphere, it is necessary
to consider the attenuation of precipitation, vapor in atmosphere and oxygen. In
telecommunication on lunar surface, the propagation media is extremely tenuous
Table 10.1 Farthest telecommunication distance and telecommunication delay of lunar probe [9]
Farthest distance/km
Increased path loss (to geostationary orbit spacecraft)/dB
Delay/s
0.4055 × 10 6
21.03
1.35