The Dish: how Parkes helped show the Moon landing

The full story

This is the episode's narration, word for word. Headings jump to that point in the video.

The question 0:00

In July 1969, an estimated six hundred million people watched a man step onto the Moon. Most of that moonwalk reached them through a radio telescope in a paddock near Parkes, New South Wales. A famous film made it Parkes' show alone. The real story is shared. So how does a dish hear a TV camera on the Moon, and who really carried which minutes?

A whisper from the Moon 0:27

The lunar module sent its TV from an antenna about two-thirds of a metre across. Across nearly four hundred thousand kilometres, those waves spread out enormously. That's the inverse-square law: double the distance, and the same power covers four times the area, so each patch gets a quarter as much. Any one dish on Earth catches only a sliver of what left the Moon.

A bucket for radio 0:54

So think of a dish as a bucket in the rain. How much it catches depends on its area, and area grows with the square of the width. Parkes is sixty-four metres across; NASA's dish at Honeysuckle Creek, near Canberra, was twenty-six. Parkes has about six times the area, so it collects about six times the power from the same source. That's why bigger dishes can hear fainter things.

Why the shape is a parabola 1:22

But collecting isn't enough: the waves have to add up in one place. A parabola does that. Waves arriving straight down its axis all bounce to a single point, the focus, and every path there is the same length, so the waves arrive in step and reinforce each other. Parkes is a prime-focus dish: its receivers sit in a cabin at the focus, about twenty-six metres above the centre of the dish. There, a horn picks up the focused waves and a receiver amplifies them.

A narrow gaze 1:56

There's a catch. A dish's sharpness depends on the wavelength divided by its width. Apollo's signal had a wavelength of about thirteen centimetres, so on a sixty-four-metre dish the beam is only about an eighth of a degree across. Point slightly off, and the signal fades. That's why Parkes also carried a second, less sensitive receiver mounted just off the focus, which looked at a patch of sky a little over a degree away. That second receiver is going to matter.

Bowen's telescope 2:30

The telescope was the project of Taffy Bowen, chief of CSIRO's Radiophysics Laboratory, a group that grew out of wartime radar. He got two American foundations, Carnegie and Rockefeller, to pay about half, and the Menzies government paid nearly all the rest. Barnes Wallis suggested the structure, the London firm Freeman Fox designed it, and a German company led the build. It opened on the thirty-first of October 1961. At the opening, the wind was so strong the dish couldn't tip down to greet the guests. Wind would come back to haunt it.

So good NASA copied it 3:10

The design worked so well that NASA modelled its big sixty-four-metre deep-space dishes on it: first at Goldstone in California, and in the 1970s near Madrid and at Tidbinbilla near Canberra. So when Apollo came along, NASA asked to borrow it. Parkes' director, John Bolton, agreed to a one-line contract: the Radiophysics Division "would agree to support the Apollo 11 mission". NASA sent four engineers, led by Robert Taylor.

Three stations, one plan 3:43

NASA's first plan made Goldstone, in California, the main station for the moonwalk, with Parkes as backup. Then, in May 1969, NASA gave the crew a rest before the walk, which would put it in the late afternoon with the Moon high over Parkes, so Parkes was upgraded to prime station. Honeysuckle Creek, run for NASA by Australian staff, was NASA's main Apollo station in Australia. And on the eighteenth of July, a transmitter fire at nearby Tidbinbilla made NASA swap the two stations' jobs, so Honeysuckle Creek ended up tracking the lunar module itself.

Armstrong goes early 4:24

Eagle landed at seventeen minutes past six in the morning, eastern Australian time. Instead of resting, the crew took the option of going out early, about five hours before the Moon would rise for Parkes. And Parkes can't point low: its dish only tips down to about thirty degrees above the horizon. But suiting up took far longer than planned, and the Moon was due to clear that limit at two minutes past one.

The wind 4:52

While the dish waited, tipped as far over as it could go, a squall hit. Gusts of over a hundred kilometres an hour slammed it back against its drive gears, and the control tower shuddered. Its safety limit then, by one account, was forty-eight kilometres an hour. Wind force rises roughly with the square of the speed, so that was several times the force at that limit. The rules said stow the dish. John Bolton checked the strain gauges and decided to keep tracking.

An upside-down Moon 5:26

The TV camera on the lunar module sent slow-scan pictures, just ten frames a second at three hundred and twenty lines. It was converted by pointing an ordinary TV camera at a special monitor. And the camera was mounted upside down, so each station had a switch to flip the picture. At six minutes to one, Buzz Aldrin switched the camera on, and Goldstone, Honeysuckle Creek and Parkes all picked it up.

Honeysuckle Creek's first step 5:56

Houston started with Goldstone, but its picture was upside down and too contrasty. At Honeysuckle Creek, video technician Ed von Renouard flipped his switch within seconds and fixed the contrast. Less than two minutes in, Houston switched to Honeysuckle Creek. So when Neil Armstrong stepped onto the Moon, at four minutes to one, the world saw it through Honeysuckle Creek's twenty-six-metre dish.

Parkes takes over 6:24

And Parkes? It had a weak signal from the start in that off-axis receiver, with Bolton turning the receiver mount while driver Fox Mason steered by a signal meter. Then the Moon rose into the main beam. About nine minutes after the camera came on, Sydney told Houston it had a good picture from Parkes. Houston replied, "Roger, beautiful picture". It stayed with Parkes for the rest of the moonwalk, about two and a half hours. Mission control's verdict: "they've given us the best TV yet".

Who carried what 7:00

So here's the honest split. For about nine minutes, Houston switched between Goldstone and Honeysuckle Creek, and Honeysuckle Creek carried the first step. Parkes carried nearly all the rest. The sound came from Goldstone the whole way through. Whether Parkes' off-axis picture could have gone out sooner is disputed; the people in Sydney remember it differently. Bolton later wrote that none of them cared who came first, but for historians, "A has to have beaten B".

What the film changed 7:33

In 2000, the comedy The Dish, from director Rob Sitch, turned this into a hit, with Sam Neill as a fictional Parkes director. CSIRO's own fact check says the wind, the early moonwalk and the off-axis receiver were real. But there was no power failure, and no friction with the Americans. The Prime Minister visited Honeysuckle Creek, not Parkes. And the film understates Honeysuckle's first minutes. The dish driver, Fox Mason, said it wasn't four people, as in the film, but probably twenty-odd.

Lighthouses in space 8:11

Between missions, and ever since, its main job has been astronomy. In 1967, Jocelyn Bell and Antony Hewish at Cambridge discovered pulsars. A pulsar is a spinning neutron star, a collapsed stellar core the size of a city, sweeping a radio beam past us like a lighthouse. From 1997, a thirteen-beam receiver let Parkes search the sky fast. It has found more than fifteen hundred pulsars, about a third of all known, including a pair of pulsars orbiting each other, a precise test of gravity.

A flash from far away 8:50

In 2007, Duncan Lorimer's team, including Matthew Bailes in Melbourne, found a single burst of radio waves in old Parkes data from 2001, lasting under five thousandths of a second. Its lower frequencies arrived later, delayed by free electrons along the way. There were far too many electrons for our own galaxy, so it came from far beyond. It was the first fast radio burst, and the team guessed hundreds might happen every day.

The microwave oven 9:23

But Parkes also kept seeing look-alike bursts nicknamed perytons, and doubts crept in. In 2015, a team including Parkes staff solved it. The perytons came from the site's microwave ovens, when someone opened the door before the timer finished. And they showed the ovens couldn't have made the 2001 burst, which strengthened the case that fast radio bursts are real signals from deep space.

Murriyang 9:52

In November 2020, at the start of NAIDOC Week, local Wiradjuri elders gave the telescope a name: Murriyang. Elder Dr Stan Grant Senior said Murriyang is the home of Biyaami, the great creator, in the stars. Only its basic structure is original now, and it's about ten thousand times more sensitive than in 1961. In 2018 and 2019 it was still helping to receive data from Voyager 2, now far beyond the planets.

Looking back 10:31

This season we've followed ten Australian stories: Wi-Fi, the black box, the bionic ear, penicillin, ultrasound, ulcers, the HPV vaccine, spray-on skin, plastic money, and the Dish. Almost every time, the honest answer to "who did it" was a team, often across borders, building on earlier work. Parkes is a fitting place to end, because its finest hour was shared with Honeysuckle Creek and Goldstone.

Next season 11:03

That's the end of our season on Australian science, and thank you for watching. Next season, we'll take on a fresh set of questions, the kind you've always wondered about, and keep asking why until the answers make sense.

Sources

Every factual claim in the episode is tied to one of these. Spotted an error? Tell us.

1. J. M. Sarkissian, "On Eagle's Wings: The Parkes Observatory's Support of the Apollo 11… — parkes.atnf.csiro.au
2. CSIRO, "Murriyang, our Parkes radio telescope" — csiro.au
3. Wikipedia, "The Dish" (film; secondary, credits and release only) — en.wikipedia.org
4. E. M. Jones (ed.), Apollo Lunar Surface Journal (NASA), "Apollo 11: One Small Step" — apollojournals.org
5. NASA Goddard Space Flight Center, "The Apollo 11 Telemetry Data Recordings: A Final… — apollojournals.org
6. HyperPhysics (R. Nave, Georgia State Univ.), "Inverse Square Law, General" — hyperphysics.phy-astr.gsu.edu
7. OpenStax, Astronomy 2e, §6.1 "Telescopes" (light-gathering ability set by the… — openstax.org
8. H. Lindsay, "Apollo 11" (Honeysuckle Creek mission history), honeysucklecreek.net — honeysucklecreek.net
9. National Radio Astronomy Observatory, "What are Radio Telescopes?" — public.nrao.edu
10. Wikipedia, "Parabolic antenna" (secondary; the paraboloid's paths from focus to… — en.wikipedia.org
11. Honeysuckle Creek Tracking Station site, "Parkes Radio Telescope, Intro" (incl. 1961… — honeysucklecreek.net
12. P. Robertson, "40 years of The Dish", ABC Science (written c. 2001 for the telescope's… — abc.net.au
13. Honeysuckle Creek Tracking Station site, "Parkes during Apollo" — honeysucklecreek.net
14. CSIRO ATNF, "The Dish: Fact vs Fiction, a quick comparison" (Wayback copy, 28 June 2014) — web.archive.org
15. HyperPhysics, "Air Friction" (drag approximately proportional to velocity squared) — hyperphysics.phy-astr.gsu.edu
16. CSIRO ATNF, "Pulsars" (education resource) — atnf.csiro.au
17. CSIRO ATNF Pulsar Catalogue, Catalogue Version 2.8.1 (Manchester et al.; 4,393… — atnf.csiro.au
18. D. R. Lorimer, M. Bailes, M. A. McLaughlin, D. J. Narkevic, F. Crawford, "A bright… — arxiv.org
19. E. Petroff et al. (incl. J. Sarkissian), "Identifying the source of perytons at the… — arxiv.org
20. ABC News (Central West), "CSIRO Parkes Radio Telescope, The Dish, given a Wiradjuri… — abc.net.au

Image credits

• Parkes radio telescope, 1969 · photo: CSIRO (ScienceImage 4350) · CC BY 3.0 · licence: https://creativecommons.org/licenses/by/3.0/
• Parkes control room, July 1969 (left to right): John Bolton, Robert Taylor (NASA), Taffy Bowen · photo: CSIRO (ScienceImage 2124) · CC BY 3.0 · licence: https://creativecommons.org/licenses/by/3.0/
• The former Honeysuckle Creek antenna, now DSS-46 at Tidbinbilla, 2024 · photo: MatthewDalhousie · CC0, via Wikimedia Commons · licence: https://creativecommons.org/publicdomain/zero/1.0/
• Apollo 11 TV, 21 July 1969 · NASA · public domain
• Murriyang, the Parkes radio telescope, 2007 · photo: David McClenaghan, CSIRO ScienceImage 3875 · CC BY 3.0 · licence: https://creativecommons.org/licenses/by/3.0/

Researched and scripted with AI assistance, fact-checked claim by claim, with synthetic narration and diagrams drawn in code. How we make episodes.