The dish spiced up

AUSTRALIAN ingenuity will save NASA about $800,000 and three months of down time when the 70-metre antenna at the Canberra Deep Space Communications Complex is shut for refurbishment in November.

Visitors gazing at the sparkling 4000-tonne dish would never know the paint has failed and is cracked and peeling, reducing its reliability.

For a piece of extremely sensitive equipment that detects radio waves sent from Voyager 1 with half as much power as a fridge light, surface consistency to 0.1 millimetre is critical.

It takes radio waves from Voyager 1 about 14 hours to reach Earth and by the time they arrive, they have faded markedly from 12 watts to 20 million times weaker than a watch battery.

Mechanical engineer John Phillips is the deputy antenna site facility manager and will be part of a team overseeing the replacement of the grout beneath the antenna and the painting of the dish. ''It will do the same function but reliability will be improved. If you get deformation in the grout that supports the runner, the antenna itself is not as good,'' Mr Phillips said.

''If you get deformation in the runner because the support isn't that good, it stops the antenna from working.''

The original plan was to jack up the antenna and bolt legs on to replace the grout in one go.

''It would have cost twice that and they were estimating down time of more than 10 months.''

The new plan will replace the grout in 60-degree sections and close it from November 12 to June 6.

The new grout is impervious to oil and should last decades. ''It's an epoxy with a crushed quartz mix. With the new grout, that should improve quality and the reliability of the antenna will have less down time.''

Speaking to the Sunday Canberra Times from his base in California, telecommunications system leader Peter Ilott said shutting down the Australian 70-metre antenna for seven months would not stop or negatively impact on any programs. ''It will be pretty much business as usual. We can use the 34-metre antennas,'' Dr Ilott said.

''The nice thing about the fact that we use orbiters as relay for our data is that orbiters have very large antennas compared to the lander. We can't put a big antenna on the lander and the orbiters can talk to the 34-metre antennas pretty much no problem. It decreases the data rate that we can transfer the data at but in general it won't affect us.''

During the refurbishment, the reflector surface of the dish will also be painted with a special paint from the United States.

Mr Phillips said the 4200-square-metre dish will need more than 1200 litres of paint. ''They are going to tip it on the side and then use our 70-metre cherrypicker and use pressure blasters to wash it all down while it's standing upright and paint it while it's in stow position,'' Mr Phillips said.

When the antenna is stowed, it faces straight up towards the sky. It will only take a couple of hours to dry.

''It's a very thin film, the pressure washing is the hard bit, it will take a few weeks. The paint has essentially failed and a lot of it is missing, or is in the process of failing. If you get up and have a good look, you'll see it's all cracked or falling off,'' Mr Phillips said.'

''If you have light spots and darks spots you have thermal distortion between the two, [repainting] it helps keep a better shape and better signal.''

The story The dish spiced up first appeared on The Sydney Morning Herald.

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