10.2 Development Status
335
probes was developed from multi-band and multi-carrier analog baseband signal to
digital baseband signal, digital modulation and unified carrier system.
The S-band unified carrier modulation system was applied in Apollo spacecraft
for the first time. For Apollo spacecraft, in circumlunar orbit, double frequencies were applied, where the S-band unified carrier system was applied for
telemetry/telecommand at one frequency and the suppressed carrier modulation
system was applied for high-speed telecommunication at another frequency. In
the unified carrier modulation, the uplink and downlink carriers are coherent. The
uplink carrier modulation had range pseudo code, telecommand and voice, while
the telecommand and voice were firstly modulated on two subcarriers to realize the
frequency separation and then to modulate the carrier with the ranging pseudo code.
The downlink carrier was modulated with ranging pseudo code, telemetry and voice,
while the telemetry and voice were also modulated on the subcarrier at first [4].
In twenty-first century, NASA launched a series of Mars surface soft-landing
probes such as Spirit, Opportunity, Phoenix and Mars Science Laboratory, and
implemented soft-landing on Martian surface successfully. The X-band unified
carrier telemetry/telecommand system and the suppression carrier modulation
system were applied for all above missions. The telecommunication band was
improved from S-band in Apollo missions to X-band. The X-band unified carrier
telemetry/telecommand system is the main system of global deep space exploration. Compared with S-band, the use of X-band can improve tracking accuracy
and realize the miniaturization of onboard instruments [6]. At the same time, the
UHF band telecommunication instruments onboard above Mars probes were used
to relay telecommunication with Mars orbiters such as Mar Odyssey, Mars Express
and Mars Reconnaissance Orbiter to forward the uplink data from ground station to
Mars probes and the downlink data from Mars probes to ground station, which could
improve the volume of engineering and scientific exploration data sent back by Mars
probes.
On October 24, 2007, Chinese first lunar probe, the Chang’E-1 was launched
successfully and the S-band unified carrier telemetry/telecommand system was
applied in the Chang’E-1. The ground telemetry/telecommand facilities were
upgraded on the basis of the original Earth orbit spacecraft telemetry/telecommand
and telecommunication facilities. In order to improve the capability of long distance
orbit measurement, the Very Long Baseline Interferometry technology in radio astronomical observation was introduced into the ground telemetry/telecommand system
[5]. On October 1, 2010, the Chang’E-2 was successfully launched. An X-band
onboard telemetry/telecommand instrument was installed on the Chang’E-2, which
successfully implemented the first on-orbit demonstration of X-band unified carrier
telemetry/telecommand technology in China. The X-band telemetry/telecommand
experiment verified the high sensitivity carrier capture technology and other technologies that were suitable for deep space exploration [6]. On February 18, 2014, the
distance of the Chang’E-2 to Earth exceeded 7 × 10
7 km, which was a new record
of deep space telemetry/telecommand and telecommunication in China.
335
probes was developed from multi-band and multi-carrier analog baseband signal to
digital baseband signal, digital modulation and unified carrier system.
The S-band unified carrier modulation system was applied in Apollo spacecraft
for the first time. For Apollo spacecraft, in circumlunar orbit, double frequencies were applied, where the S-band unified carrier system was applied for
telemetry/telecommand at one frequency and the suppressed carrier modulation
system was applied for high-speed telecommunication at another frequency. In
the unified carrier modulation, the uplink and downlink carriers are coherent. The
uplink carrier modulation had range pseudo code, telecommand and voice, while
the telecommand and voice were firstly modulated on two subcarriers to realize the
frequency separation and then to modulate the carrier with the ranging pseudo code.
The downlink carrier was modulated with ranging pseudo code, telemetry and voice,
while the telemetry and voice were also modulated on the subcarrier at first [4].
In twenty-first century, NASA launched a series of Mars surface soft-landing
probes such as Spirit, Opportunity, Phoenix and Mars Science Laboratory, and
implemented soft-landing on Martian surface successfully. The X-band unified
carrier telemetry/telecommand system and the suppression carrier modulation
system were applied for all above missions. The telecommunication band was
improved from S-band in Apollo missions to X-band. The X-band unified carrier
telemetry/telecommand system is the main system of global deep space exploration. Compared with S-band, the use of X-band can improve tracking accuracy
and realize the miniaturization of onboard instruments [6]. At the same time, the
UHF band telecommunication instruments onboard above Mars probes were used
to relay telecommunication with Mars orbiters such as Mar Odyssey, Mars Express
and Mars Reconnaissance Orbiter to forward the uplink data from ground station to
Mars probes and the downlink data from Mars probes to ground station, which could
improve the volume of engineering and scientific exploration data sent back by Mars
probes.
On October 24, 2007, Chinese first lunar probe, the Chang’E-1 was launched
successfully and the S-band unified carrier telemetry/telecommand system was
applied in the Chang’E-1. The ground telemetry/telecommand facilities were
upgraded on the basis of the original Earth orbit spacecraft telemetry/telecommand
and telecommunication facilities. In order to improve the capability of long distance
orbit measurement, the Very Long Baseline Interferometry technology in radio astronomical observation was introduced into the ground telemetry/telecommand system
[5]. On October 1, 2010, the Chang’E-2 was successfully launched. An X-band
onboard telemetry/telecommand instrument was installed on the Chang’E-2, which
successfully implemented the first on-orbit demonstration of X-band unified carrier
telemetry/telecommand technology in China. The X-band telemetry/telecommand
experiment verified the high sensitivity carrier capture technology and other technologies that were suitable for deep space exploration [6]. On February 18, 2014, the
distance of the Chang’E-2 to Earth exceeded 7 × 10
7 km, which was a new record
of deep space telemetry/telecommand and telecommunication in China.