Deepspace 14

The Goldstone, California radio antenna is in need of major repairs. …

March 08, 2010

The "Mars antenna", NASA's Deep Space Network's 230-foot antenna, which has received data and sent commands to deep space missions for over 40 years, will replace a portion of the hydrostatic bearing that enables the antenna to rotate.

This means lifting 4,000 tonnes (9 million pounds) 2/10ths of an inch to replace the steel runner, walls and supporting grout for the first time.

The operation will cost about $1.25 million and last 20 years.

Presumably by then they will design compartmentalised refitting modules? Two other 70-meter antennas at Deep Space complexes near Madrid, Spain, and Canberra, Australia and arraying several smaller 34-meter (110-foot) antennas together will keep present projects in line.

The Mars antenna was the first designed to receive and transmit signals far out into space. Smaller antennae tracking the Mariner 4 spacecraft, lost contact after its "flyby" of Mars. In its history, it supported the Pioneer and Cassini missions and the Mars Exploration Rovers. It received Neil Armstrong's famous communiqué from Apollo 11: "That's one small step for man. One giant leap for mankind."

[Park in Australia got that according the the film "The Dish". And the less famous but much more piquant intro to the more often quoted phrase was:
"Hello Houston. This is Tranquillity Base."]

It has also helped with imaging nearby planets, asteroids and comets by bouncing its powerful radar signal off the objects of study.

A flat, stable surface is critical for the Mars antenna to rotate slowly as it tracks spacecraft. Three steel pads support the weight of the antenna rotating structure, dish and other communications equipment above the circular steel runner. A 0.25 mm film of oil floats the three pads. Oil leaks degraded the original grout, requiring a weekly schedule to adjust shims underneath the runner.

"As with any large, rotating structure that has operated almost 24 hours per day, seven days per week for over 40 years, we eventually have to replace major elements," said Wayne Sible, the network's deputy project manager at JPL. A new epoxy grout, impervious to oil and a thicker runner with tighter joints should get things running smoothly again.

"The runner replacement task has been in development for close to two years," said JPL's Peter Hames, who is responsible for maintaining 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. We've had to make sure we've reviewed it for practicality and safety."

[Famous last words?]

More information about the Deep Space Network is online at: http://deepspace.jpl.nasa.gov/dsn/index.html

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