Like the knees of many other middle-aged
workers, the joints of the enormous Mars Antenna need replacing. The giant
radio dish is a crucial element of NASA's Deep Space Network, and has worked
tirelessly at its location in Goldstone, Calif., for over 40 years.
This historic antenna, which measures 230
feet in diameter (70 meters) and communicates with deep space missions, once received Neil
Armstrong's famous Apollo 11 message: "That's one small step for man;
one giant leap for mankind."
Now, this laborer needs replacement of a
portion of its hydrostatic bearing assembly, the system that enables the antenna
to rotate horizontally. The repair will be no mean feat: It involves lifting 9
million lbs (4 million kg) of delicate scientific equipment 0.2 inches (5 mm),
in order to allow the replacement of the steel runner, walls and supporting
grout, which has never been done before.
The $1.25 million upgrade is expected to keep
the antenna working for 20 years. The Deep Space Network is managed by NASA's Jet Propulsion
Laboratory (JPL) in Pasadena, Calif.
"This antenna has been a workhorse for
NASA/JPL for over 40 years," said Alaudin Bhanji, Deep Space Network project
manager at JPL. "It has provided a critical lifeline to dozens of
missions, while enabling scientific results that have enriched the hearts and
minds of generations. We want it to continue doing so."
The task's scale will limit the speed of
repairs, expected to complete in early November. Workers will also replace the
elevation bearings, which enable the antenna to track up and down from the
horizon. The Deep Space Network will still communicate with space missions by
maximizing use of the two other 70-meter antennas at complexes near Madrid,
Spain, and Canberra, Australia, and arraying several smaller 34-meter
(110-foot) antennas together.
NASA built the Mars Antenna when the first
space missions began venturing beyond Earth's orbit. The antenna was the first
giant dish designed to receive weak signals and transmit very strong ones far
out into space. The antenna featured a 210-foot (64-meter-wide) dish when it
became operational in 1966 (later upgraded to 70 meters in 1988 to enable the
antenna to track Voyager 2).
Officially named Deep Space Station 14, the
antenna picked up the Mars name after its first task: tracking the Mariner
4 spacecraft, lost by smaller antennas after its historic flyby of Mars. The
Mars antenna has also supported missions including Pioneer, Cassini and the
Mars Exploration Rovers.
The antenna rotating structure, dish and
other communications equipment sit on three steel pads above a circular steel
runner, oiled by a hydraulic system. After decades of constant use, oil seeped
through the runner joints, degrading the structural integrity of the
cement-based grout supporting it. Rather than constantly adjusting shims
underneath the runner to keep it flat, Deep Space Network managers decided to
replace the whole runner assembly.
"The runner replacement task has been in development
for close to two years," said JPL's Peter Hames, who maintains the
network's antennas. "We've been testing and evaluating modern epoxy
grouts, which were unavailable when the antenna was built, updating the design
of the runner and designing a replacement process that has to be performed
without completely disassembling the antenna."
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