4.8 Ground Navigation Networks for Spacecrafts
261
IND is not only best known for its duties relating to the DSN, but also maintains the
advanced multi-mission operation system and the institutional computing and information services for the JPL. For the DSN, the specific TT&C tasks are: to acquire
the telemetry data from spacecrafts, to send TT&C commands to the spacecrafts, to
upload the updated software to the spacecrafts, to carry out the VLBI, to conduct
radio scientific tests, to detect radio wave anomalies, to collect scientific detection
data, to monitor and control the network’s performance, etc.
Since the beginning of the Voyager Interstellar Missions in the early 1990s,
the general capabilities of the DSN have not substantially changed. Certainly, the
advancement in digital signal processing, arraying and error correcting has been
adopted by the DSN. The capability to array several antennas was incorporated to
improve the data returned from the Voyager-2 encountering the Neptune. Later, the
capability was extensively used in the Galileo exploration mission for the Jupiter,
when the high-gain antenna was deployed incorrectly. Since performing the Galileo
mission, the DSN array is currently available, in which the 70-m dish-shaped antenna
at the Goldstone Station in California can link with an identical antenna located in
Australia, and two 34-m antennas at the Tidbinbilla Station in Canberra. The California and Australia sites had been used concurrently to pick up communications with
the Galileo spacecraft, which was an American automatic space probe that studied
the Jupiter and its moons, as well as other celestial bodies in the solar system, sent
into the orbit in 1990. Arraying of antennas within the three DSN stations is also used.
For example, a 70-m dish-shaped antenna can be arrayed with a 34-m dish-shaped
antenna. For especially vital missions, like the Voyager probes, the Canberra 70-m
dish can be arrayed with the Parkes Radio Telescope in Australia, and the Goldstone
70-m dish is arrayed with the very large array of antennas in New Mexico. In addition,
two or more 34 m dishes at the same DSN station are commonly arrayed together. All
of the stations are remotely operated from a centralized signal processing center at
each complex. These centers house the electronic subsystems that point and control
the antennas, receive and process the telemetry data, transmit commands and generate
the navigation data for spacecrafts. Once the data is processed at the complexes, it
is transmitted to the JPL for further processing and for distribution to the relevant
science teams over modern communication network.
There are a number of limitations to the current DSN, and a number of challenges
going forward. It is noted that the Deep Space Network is something of misnomer,
as there are no current plans, nor future plans, for exclusive communication satellites
anywhere in space to handle multiparty, multi-mission uses. All of the transmitting
and receiving equipment are the ground based. Thereby, data transmission rates
from and to any and all spacecrafts and space probes are severely constrained due
to the distances from the Earth. The DSN is required to support the legacy missions
that have remained operational beyond their original lifetime but are still returning
scientific data. For example, the Voyager missions have been operating long past
their original mission termination date. The programs like the Voyager also need
some of the largest antennas. Replacing major components can cause problems as it
will leave an antenna out of service for months at a time. The older 70-m antennas
are reaching the end of their lives. At some point these will need to be replaced.
261
IND is not only best known for its duties relating to the DSN, but also maintains the
advanced multi-mission operation system and the institutional computing and information services for the JPL. For the DSN, the specific TT&C tasks are: to acquire
the telemetry data from spacecrafts, to send TT&C commands to the spacecrafts, to
upload the updated software to the spacecrafts, to carry out the VLBI, to conduct
radio scientific tests, to detect radio wave anomalies, to collect scientific detection
data, to monitor and control the network’s performance, etc.
Since the beginning of the Voyager Interstellar Missions in the early 1990s,
the general capabilities of the DSN have not substantially changed. Certainly, the
advancement in digital signal processing, arraying and error correcting has been
adopted by the DSN. The capability to array several antennas was incorporated to
improve the data returned from the Voyager-2 encountering the Neptune. Later, the
capability was extensively used in the Galileo exploration mission for the Jupiter,
when the high-gain antenna was deployed incorrectly. Since performing the Galileo
mission, the DSN array is currently available, in which the 70-m dish-shaped antenna
at the Goldstone Station in California can link with an identical antenna located in
Australia, and two 34-m antennas at the Tidbinbilla Station in Canberra. The California and Australia sites had been used concurrently to pick up communications with
the Galileo spacecraft, which was an American automatic space probe that studied
the Jupiter and its moons, as well as other celestial bodies in the solar system, sent
into the orbit in 1990. Arraying of antennas within the three DSN stations is also used.
For example, a 70-m dish-shaped antenna can be arrayed with a 34-m dish-shaped
antenna. For especially vital missions, like the Voyager probes, the Canberra 70-m
dish can be arrayed with the Parkes Radio Telescope in Australia, and the Goldstone
70-m dish is arrayed with the very large array of antennas in New Mexico. In addition,
two or more 34 m dishes at the same DSN station are commonly arrayed together. All
of the stations are remotely operated from a centralized signal processing center at
each complex. These centers house the electronic subsystems that point and control
the antennas, receive and process the telemetry data, transmit commands and generate
the navigation data for spacecrafts. Once the data is processed at the complexes, it
is transmitted to the JPL for further processing and for distribution to the relevant
science teams over modern communication network.
There are a number of limitations to the current DSN, and a number of challenges
going forward. It is noted that the Deep Space Network is something of misnomer,
as there are no current plans, nor future plans, for exclusive communication satellites
anywhere in space to handle multiparty, multi-mission uses. All of the transmitting
and receiving equipment are the ground based. Thereby, data transmission rates
from and to any and all spacecrafts and space probes are severely constrained due
to the distances from the Earth. The DSN is required to support the legacy missions
that have remained operational beyond their original lifetime but are still returning
scientific data. For example, the Voyager missions have been operating long past
their original mission termination date. The programs like the Voyager also need
some of the largest antennas. Replacing major components can cause problems as it
will leave an antenna out of service for months at a time. The older 70-m antennas
are reaching the end of their lives. At some point these will need to be replaced.