By Norm and Chrissy Siggee

The Parkes Observatory, originally commissioned in 1961, is normally used as a deep space radio telescope gathering data from astronomical observations. However, because of the sensitivity of the dish, it has also been used to track and receive data from space probes including the Galileo probe to Jupiter and various missions to Mars. Located in the middle of a sheep paddock 20 km (12 miles) north of the central New South Wales town of Parkes, the Parkes Observatory, with its giant 64 metre (or 210 feet) dish, is an integral part of the Australia Telescope National Facility.

This radio telescope became famous for the television imagery that the estimated 600 million people worldwide watched at 12.56 pm Australian Eastern Standard Time on Monday 21st July 1969: the moon walk of Neil Armstrong and Buzz Aldrin.

When Neil Armstrong stepped onto the surface of the moon, three tracking stations were providing imagery to Houston – Parkes, Honeysuckle Creek outside of Canberra and Goldstone Station in California. The vastly superior quality of the imagery being supplied by Parkes resulted in NASA remaining with the Parkes TV pictures for the 2 ½ hour broadcast.

The event almost didn’t happen. Just prior to the walk, Parkes was hit with wind gusts of up to 110 km per hour (70 miles per hour) while the dish was fully tipped over. The moon was at that time just below the Parkes horizon. With the wind threatening the structural integrity of the telescope structure, it appeared that Parkes may not be able to be part of the historic event. Fortunately, due to delays experienced by Neil Armstrong in depressurizing the lunar module, with the moon starting to peer over the horizon and using a less sensitive off-axis detector, Parkes was able to receive the TV pictures as soon as the lunar camera was turned on. Less than nine minutes later, Parkes switched to their main detector when the moon was fully raised providing the high quality images that the rest of the world saw.

The images from Parkes were sent by microwave link to Sydney where the signal was split in two: one being sent to Australian television networks and the other through the communications satellite INTELSAT to Houston.

Here is the good news for Australians. Because the international broadcast signal had to travel halfway around the world from Sydney to Houston a 300 millisecond delay was introduced to the signal. Australian audiences therefore witnessed the moonwalk, and Armstrong’s historic first step, some 0.3 seconds before the rest of the world.

For a light-hearted account of the role of the Parkes Observatory watch the film ‘The Dish’ (2000) starring Sam Neill (“Jurassic Park” & “Hunt for Red October”), Kevin Harrington, Tom Long and Patrick Warburton (“Seinfeld”) was produced. Be warned: it contains some Australian humour.

References:
Sarkissan, John (2001) On Eagles Wings, Publications of the Australian Astronomical Society, Vol 18, No 3 downloaded from http://www.parkes.atnf.csiro.au/news_events/apollo11/ on 17 July 2009.
Apollo 11 moon landing: celebrating 40 years http://www.csiro.au/science/Apollo-11-and-Parkes-telescope.html
IMBD – The Dish http://www.imdb.com/title/tt0205873/
Parkes Telescope Image location http://www.csiro.au/files/images/pr9f.jpg

Black and white telescope image. http://www.parkes.atnf.csiro.au/news_events/apollo11/images/1960s_telescope.jpg

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