10.5 Testing and Verification
361
on the interface check such as antenna polarization compliance, zero distance in
telemetry/telecommand channel.
Generally, the uplink and downlink radio signal characteristics check included
the modulation characteristics such as the modulation mode and modulation degree
of the uplink and downlink signals, and the format check of the uplink telecommand,
injected data, downlink telemetry and telecommunication data, and the check of the
demodulation performance, etc. Tracking was one of the keys for success of spacecraft mission. Therefore, the other major work in the process of wired interface test
was check of the joint operation of spacecraft onboard telemetry/telecommand instruments and ground telemetry/telecommand system for the measurement of speed,
distance and angle.
In order to avoid the influence of Earth atmosphere on the radio propagation
channel, the antenna of spacecraft telemetry/telecommand and telecommunication subsystem was generally selected as circular polarization antenna. The modes
of circular polarization included left handed and right handed circular polarizations. The antenna polarization method would be settled by spacecraft, ground
telemetry/telecommand and ground application to avoid influence on the normal
reception of uplink and downlink radio frequency signals between spacecraft and
ground station. Therefore, the verification of antenna polarization was one of the
important jobs in wireless interface test. And the time delay characteristics of the
distance measurement signal sent by ground telemetry/telecommunication station
and the received ranging signal was used by ground telemetry/telecommunication
system to calculate the distance of spacecraft to ground. The distance measurement
signal would introduce the delay variation of the fixed value during transferred with
the spacecraft onboard telemetry/telecommand instruments, which was called the
zero distance value of telemetry/telecommand channel. During test of interface, the
zero value must be calibrated, which was one of the bases for distance measurement
of spacecraft on orbit.
10.5.3 UHF Field Test
In order to verify the correctness of UHF band telecommunication system on lunar
surface, according to environment characteristics on lunar surface, a test field on
Earth desert was selected for telecommunication verification on lunar surface when
the Chang’E-3 lunar probes were developed. The transmission characteristics of
UHF band telecommunication link under desert environment were tested, and UHF
band telecommunication subsystem was verified. The block diagram of ground test
system for telecommunication on lunar surface is shown in Fig. 10.15.
According to actual terrain of the test field, three paths were planned as the UHF
band transmitter’s moving direction with UHF band receiver of the lunar lander as
the center and 3 km as the radius. The top view of the terrain of the test field for UHF
band telecommunication on lunar surface and planned paths is shown in Fig. 10.16.
361
on the interface check such as antenna polarization compliance, zero distance in
telemetry/telecommand channel.
Generally, the uplink and downlink radio signal characteristics check included
the modulation characteristics such as the modulation mode and modulation degree
of the uplink and downlink signals, and the format check of the uplink telecommand,
injected data, downlink telemetry and telecommunication data, and the check of the
demodulation performance, etc. Tracking was one of the keys for success of spacecraft mission. Therefore, the other major work in the process of wired interface test
was check of the joint operation of spacecraft onboard telemetry/telecommand instruments and ground telemetry/telecommand system for the measurement of speed,
distance and angle.
In order to avoid the influence of Earth atmosphere on the radio propagation
channel, the antenna of spacecraft telemetry/telecommand and telecommunication subsystem was generally selected as circular polarization antenna. The modes
of circular polarization included left handed and right handed circular polarizations. The antenna polarization method would be settled by spacecraft, ground
telemetry/telecommand and ground application to avoid influence on the normal
reception of uplink and downlink radio frequency signals between spacecraft and
ground station. Therefore, the verification of antenna polarization was one of the
important jobs in wireless interface test. And the time delay characteristics of the
distance measurement signal sent by ground telemetry/telecommunication station
and the received ranging signal was used by ground telemetry/telecommunication
system to calculate the distance of spacecraft to ground. The distance measurement
signal would introduce the delay variation of the fixed value during transferred with
the spacecraft onboard telemetry/telecommand instruments, which was called the
zero distance value of telemetry/telecommand channel. During test of interface, the
zero value must be calibrated, which was one of the bases for distance measurement
of spacecraft on orbit.
10.5.3 UHF Field Test
In order to verify the correctness of UHF band telecommunication system on lunar
surface, according to environment characteristics on lunar surface, a test field on
Earth desert was selected for telecommunication verification on lunar surface when
the Chang’E-3 lunar probes were developed. The transmission characteristics of
UHF band telecommunication link under desert environment were tested, and UHF
band telecommunication subsystem was verified. The block diagram of ground test
system for telecommunication on lunar surface is shown in Fig. 10.15.
According to actual terrain of the test field, three paths were planned as the UHF
band transmitter’s moving direction with UHF band receiver of the lunar lander as
the center and 3 km as the radius. The top view of the terrain of the test field for UHF
band telecommunication on lunar surface and planned paths is shown in Fig. 10.16.