HAMNET Report 14 July 2019

Dan Falk, writing on the Smithsonian.com website summarises some interesting backroom radio events in his report on the Apollo moon landing 50 years ago this week.

The Apollo lunar module had a transmitter for sending back not only TV images but also crucial telemetry, radio communications and the astronaut’s biomedical data—but receiving those signals was no simple matter. The transmitter had a power output of just 20 watts, about the same as a refrigerator light bulb, and picking up that signal from the moon a quarter of a million miles away required huge, dish-shaped antennas. Moreover, as the Earth turns, the moon is only above the horizon for half the day at any one receiving station. So NASA relied on ground stations on three different continents, located at Goldstone, in California’s Mojave Desert, in central Spain, and in south eastern Australia. To this day, these radio stations make up the Deep Space Network, allowing NASA to monitor all parts of the sky for communications at all times.

The critical moment when Armstrong and Aldrin were due to leave the lunar module and step out onto the moon’s surface was initially scheduled for noon, eastern Australia time, which would have put the giant 64-metre dish at Parkes, New South Wales, in prime position to receive the signal.

But all did not go according to plan. The astronauts, eager to leave the spacecraft, decided to skip their scheduled rest break and began preparing for their moonwalk some six hours ahead of schedule, forcing the Australian antennas to aim just above the horizon, rather than overhead. Because of its design, however, Parkes can’t tilt its huge dish any lower than 30 degrees above the horizon. And to complicate matters, it was just then that the windstorm of a lifetime kicked in, with gusts of 60 miles an hour buffeting the giant Parkes dish.

With the winds howling at dangerous speeds, normal protocols would have called for a halt to telescope operations—but this was humankind’s first visit to another world, and the rules were bent. Parkes director John Bolton gave the go-ahead to keep the dish operating.

Fortunately for the Parkes crew, the astronauts took longer than expected to put on their spacesuits and depressurize the lunar module in preparation for the moonwalk, allowing the moon to rise a bit higher in the sky and align with the big dish’s line of sight. And even more fortunately, the delay allowed the storm to blow over. The wind eventually subsided, allowing the telescope to lock onto the Apollo signal.

Controllers in Houston could choose which feed to send out to the TV networks, and in the end telescopes in both California and Australia played a role. Viewers around the world saw the superior images from the enormous Parkes dish—and remained on Parkes for the majority of the two-and-a-half-hour lunar walkabout.

Most viewers would have known nothing of the windstorm at Parkes—or even of the giant dish that played such a vital role in the historic broadcast.

Parkes remains a world-class radio observatory, known for the first detection of Fast Radio Bursts (mysterious bursts of energy from deep space) and for participating in the search for extra-terrestrial civilizations as part of the Breakthrough Listen project. The giant dish also continues to track NASA spacecraft, including Voyager 2, now some 18 billion kilometres from Earth.

Most of the scientists, who work at Parkes today, though too young to remember Apollo, are still keenly aware of the history that surrounds them.

Thank you to Smithsonian.com for the extracts from Dan Falk’s report.

ARRL News says that the Hurricane Watch Net (HWN) and WX4NHC— the Amateur Radio station at the National Hurricane Centre (NHC) in Miami — have announced plans to activate, as Tropical Storm Barry approaches the coast of Louisiana and Mississippi. The HWN activated yesterday (July 13) at 01h00 UTC on both 14.325 MHz and 7.268 MHz.

Graves said that once the net activates on Saturday, it will remain in operation until further notice. He said that the HWN also will be available to provide back-up communication to official agencies in the affected area and will be collecting and reporting “significant damage assessment data” to FEMA officials at the National Hurricane Centre.

“We encourage all ham operators in the affected area to take all safety precautions needed and comply with evacuation orders from authorities,” WX4NHC Assistant Manager Julio Ripoli, WD4R, said. The Hurricane Watch Net and WX4NHC typically coordinate their activities, with the HWN reporting weather data observed by participants to the NHC via WX4NHC.

Hurricane hunters report that Tropical Storm Barry is gaining strength. Forecasters predict additional strengthening before landfall; Barry is expected to be a hurricane when the centre reaches the Louisiana coast. The NHC says dangerous storm surge, heavy rainfall, and high wind conditions are expected across the north-central Gulf Coast.

The heavy rainfall could generate additional flooding in the region. According to NHC forecasters, Barry is expected to produce total rain accumulations of 10 to 20 inches over south-central and southeast Louisiana as well as over southwest Mississippi, with isolated maximum amounts of 25 inches. “These rains are expected to lead to dangerous, life-threatening flooding over portions of the central Gulf Coast into the Lower Mississippi Valley,” the NHC forecast said.

Please be mindful of emergency nets on 14.325MHz or 7.268MHz, or thereabouts, in the next few days, and maintain radio silence if you hear traffic there.

In a combined report regarding rescues on Table Mountain, written last week, Wilderness Search and Rescue commends three aspects of rescue worth, which showed themselves in a 12 hour period.

Firstly, some of the parties that needed rescuing were able to drop WhatsApp pins on their phone Apps to pinpoint their positions. This is a marvellous development in modern smartphone technology, and made the job, for searchers finding them, considerably easier.

Secondly, the Table Mountain Aerial Cableway Company is always ready to assist in bringing injured or rescued people off the mountain, if the weather allows it.

And thirdly, responders, all of them volunteers, are ready and willing to go back and rescue another person or party, even though they have just come off a challenging and arduous rescue. They are all to be highly commended for this.

In the weekend under consideration, four rescues took place within 12 hours, interestingly involving 11 hikers, 3 from Australia, 2 from the USA, 1 from France and 2 from the Netherlands, with 3 local hikers in the Australian party.

We can only be grateful to the climbers, 4-wheel drive enthusiasts and HAMNET members, who brought all these people safely down.

This is Dave Reece  ZS1DFR  reporting for HAMNET in South Africa.