Date: March 2, 2010
Title: The Parkes Dish
Podcaster: Eran Segev
Organization: The Skeptic Zone Podcast – www.skepticzone.tv
Description: The 64 metre radio telescope at Parkes in NSW, Australia played an important role in the first moon landing. This is the story of that day and the experiences of some of those who were there.
Bio: Eran Segev is an IT consultant, but his passion is science in general and astronomy in particular. He is the President of Australian Skeptics (www.skeptics.com.au) and participates in the Skeptic Zone podcast (www.skepticzone.tv).
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Mick Vagg, a grassroots astronomy punter in appreciation of the efforts of all contributors to the 365 Days of Astronomy project. Thanks for keeping me interested on those all too frequent cloudy nights!
This is Eran Segev from Australian Skeptics and the Skeptic Zone podcast, with the story of Parkes, a small town 380km west of Sydney.
Monday, the 21st of July 1969 was a very special day for Parkes. While most of the world remembers the first landing on the moon as having happened on the 20th of July, the time difference between Australia and the US means that when the Eagle landed in the Sea of Tranquillity at 4:18PM EDT, it was 6:18AM of the following day at Parkes. The reason that that event has special meaning for Parkes is that it is host to a 64 metre radio telescope which played an important role in that momentous event.
Two members of the Parkes team who were there during the crucial hours in 1969 are Neil “Fox” Mason, who was responsible for driving the telescope, and Cliff Smith, who was in charge of telescope maintenance. Neil and Cliff agreed to share some of their experiences with me.
The radio telescope at Parkes is operated by the CSIRO, Australia’s Scientific and Industrial Research Organisation. It started operations in 1961 as the brainchild of Taffy Bowen, the Chief of CSIRO’s Radiophysics Division and was headed by John Bolton, a legendary radio astronomer. To this day, it is one of the largest radio telescopes in the world. In the Southern hemisphere, it is only surpassed by Tidbinbilla, near Canberra in Australia, and Arecibo in Puerto Rico, which is not a moveable dish.
In the mid to late 1960’s, the Parkes dish became part of NASA’s Deep Space Network.
Fox Mason explains why Parkes was chosen to be involved with Apollo 11:
“We had tracked different flights at different times, but Tidbinbilla was the main NASA tracking station, down in Canberra, and it was a smaller dish. Why they got Parkes for the Apollo 11 was because of the television pictures and things coming back and we got a greater collecting surface. We were the biggest steerable dish in the Southern hemisphere at the time”
At the time of the moon landing, the tracking station communicating with Apollo 11 was Goldstone, in California. As is now well known, the original plan was for Neil Armstrong and Buzz Aldrin to sleep for six hours before preparing for the EVA. This would have seen them leave the LM about 10 hours after landing, by which time the moon would have been under the horizon for Goldstone and Parkes would have been tasked with receiving the TV transmissions from the first human steps on another world.
Fox Mason describes the preparations at Parkes:
“First up at about, I don’t know, about 11:30, we tipped the dish over just to check the receivers were working ok and the pointing was correct. We went and calibrated on one of the radio sources that was particularly well know at the time, Hydra A, and then we calibrated the… checked our pointing, and the calibration of the receivers then after that we spent about an hour and then I suppose and then we got the dish into position and tipped the dish right down so it was pointing at the horizon so we were in a very vulnerable position tipped right over the 60 degrees waiting for the moon to rise”
As it turned out, Neil and Buzz were not in the mood for sleep – no prizes for guessing why – and asked for permission to go ahead with the EVA immediately. Permission was granted and they started preparing.
For Parkes, this looked like all the hard work they had put in, in anticipation of the landing, would come to naught. However, Aldrin and Armstrong took longer than expected to prepare for the EVA
Fox Mason recalls:
“They were going to have a sleep and then come later on in the day, but once they got there they were too excited they wanted to get out there as quickly as they could. But then they had trouble depressurising their spaceship and getting their space suits on so by the time they were ready, Parkes was just about ready as well.”
The delay meant that six hours later the astronauts were still not quite ready to step out of the LM, and time was running out for Goldstone. Unfortunately, the moon had not yet risen at Parkes, but there was still some time to go before the EVA.
Meanwhile on the ground, the weather took a turn for the worse. July is the middle of winter in Australia and as everyone was waiting for the EVA the wind around Parkes picked up. This was particularly bad news as the dish was at its maximum tilt of 60 degrees in order to receive the signal from the moon as soon as it rose.
Cliff Smith was outside in the wind, and he tells his story:
“We didn’t expect what happened, but for twenty minutes of the first observing period it blew and a squall hit us and in fact where I was at the back of the telescope to make sure everything stayed that way, as good as it was; because as you well know that telescope is one of the best sails you ever saw.”
And it was not in a position for this kind of storm, was it?
“It was not. It blew in from the west and unfortunately we were pointing east.”
As Cliff said, under normal circumstances the dish, a 64 metre sail weighing 300 tons, would not be allowed to be subjected to such winds, which were in excess of 100kph, without being aimed at the zenith and anchored, as there was a real risk of catastrophic failure. However, these were not normal circumstances, and John Bolton and Taffy Bowen decided to take the risk. As the moon was approaching the horizon and the astronauts were getting ready to leave the LM, the wind subsided.
At 12:54PM local time, just as the moon rose over the horizon at Parkes and John Bolton managed to get a signal on the off-axis receiver, Aldrin activated the TV signal.
Fox Mason was not watching, as he was busy tracking the signal:
“No, I wasn’t able to watch at the time, because I was too busy, engrossed in my own task, keeping the dish pointed in the right area.”
Can you tell us how the physical tracking was done? How did you know you were pointing in the right direction?
“Well, we had sets of coordinates that ANSA had sent us and then we checked all the positions and found them ok and then we had a voltmeter up on top of the desk so we could see when we were getting the strongest signal all the time.”
So basically every time the signal got a bit weaker you moved in the direction that you thought was right?
“Moved it, yes, a little bit one way or the other, either in azimuth or declination to pick up on the best signal.”
The signal was also picked up by the 64 metre dish at Goldstone and by the 26 metre dish at Honeysuckle creek near Canberra. For a few minutes NASA alternated between the signals in search of the best picture, but after 9 minutes the moon was high enough over the horizon for the signal to be received by the main detector at Parkes and for the rest of the moon walk, the Parkes transmission was used.
Naturally, those who were involved in the moon landing have an opinion about the moon landing hoax believers, so I asked Fox and Cliff what they thought of the conspiracy theorists.
Fox Mason recalls a visit by Phil Plait in 2004, a visit which I was lucky enough to be part of:
“There was an author come up here, a skeptic, Philip Plait, he made a good book about bad astronomy and all the rest of it. I mean, a lot of people still think it was made in Disneyland and we’ve never been to the moon. I don’t know what we’ve got to do to convince them. A lot of people, you’d never convince them of anything unless they can see and touch it themselves and that’s the nature of human beings, I suppose.”
Cliff Smith in turn, offers the best evidence he can that Neil and Buzz really walked on the moon:
“Well as a matter of fact, I’m led to believe and I’m sure this happened, was the fact that we pointed the telescope at the moon, and we got a signal. Not only once, but we got a signal on the offset aerial and we got a signal on the main aerial. And if they sent that from the Mojave Desert as those clowns say we must have, somebody must have been up there to have an echoing chamber or something like that. We received the signal from the moon, is all I know.”
There is a lot more to tell about the dish at Parkes. For more information and the full story, go to www.parkes.atnf.csiro.au/news_events/apollo11. To hear the full interviews with Fox Mason and Cliff Smith, go to the website of the Skeptic Zone podcast – www.skepticzone.tv.
Thank you for listening to the 365 Days of Astronomy podcast.
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the Astrosphere New Media Association. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.