HAMNET Report 29th October 2023

The tropical cyclone belt is currently peppered with cyclones. Tropical Cyclone HAMOON is threatening 4.6 million people in Bangladesh, India and Myanmar, LOLA has already attacked the island of Vanuata, and the Solomon Islands, with 70000 people in danger, and NORMA has damaged the west coast of Mexico, affecting about 400000 people.

On Tuesday of this week, a new one arose in the Eastern Pacific, again threatening more than a million people on the west coast of Mexico with over 200km/h winds, and called OTIS.

The IARU Region 2 issued a statement on Wednesday, saying that, in the early hours of Wednesday, October 25, some states of Mexico with Pacific coasts received the impact of intense Hurricane Otis.

OTIS made landfall over the area of the coastal city of Acapulco, central Guerrero State, southern Mexico on 25 October around 6.25 UTC, with maximum sustained winds of 270 km/h as a Category 5 Hurricane, the strongest ever measured there.

By Thursday, 27 fatalities in Acapulco had been reported. Parks, buildings and streets were damaged, roofs ripped off homes and hotels, and all communications were interrupted, as were electricity supplies. OTIS wrecked the airport’s control tower, preventing all air traffic from arriving or leaving.

Due to the severe impact of the storm, communications in the area collapsed completely, posing challenges to government, emergency and first responder agencies working to assess the extent of damage and impact on residents of the area. Initial reports from the Mexico Defence Ministry indicate both ground and air travel is unavailable.

For the work carried out there by the emergency networks of the Mexican Federation of Radio Experimenters and the Association of Radio Amateurs of the Mexican Republic, they are requesting the protection of the following frequencies:

80m band: 3690 kHz
40m band: 7060 kHz and 7095 kHz.                                                                              
20m band: 14 120kHz

They would appreciate the protection of those frequencies to facilitate emergency communications for Mexican colleagues.

The communique was signed by Carlos CO2JC, IARU Region 2 emcomm coordinator.

The ARRL’s hurricane watch net was also activated at the National Hurricane Centre WX4NHC, on Wednesday, monitoring the frequencies of 14.325MHz and 7.268MHz, Winlink reports, and using the VoIP hurricane net.

Phys.org tells us this week that some 30 years ago, a young engineer named Christopher Walker was home in the evening making chocolate pudding when he got what turned out to be a very serendipitous call from his mother.

Taking the call, he shut off the stove and stretched plastic wrap over the pot to keep the pudding fresh. By the time he returned, the cooling air in the pot had drawn the wrap into a concave shape, and in that warped plastic, he saw something—the magnified reflection of an overhead lightbulb—that gave him an idea that could revolutionize space-based sensing and communications.

That idea became the Large Balloon Reflector (LBR), an inflatable device that creates wide collection apertures that weigh a fraction of today’s deployable antennas. Now, with the assistance of NASA’s Innovative Advanced Concepts (NIAC) program, funded by the agency’s Space Technology Mission Directorate, which supports visionary innovations from diverse sources, Walker’s decades-old vision is coming to fruition.

The concept turns part of the inside surface of an inflated sphere into a parabolic antenna. A section comprising about a third of the balloon’s interior surface is aluminized, giving it reflective properties.

With NIAC funding, and a grant from the U.S. Naval Research Laboratory, Walker was able to develop and demonstrate technologies for a 10 metre LBR that was carried to the stratosphere by a giant balloon. For comparison, the aperture of NASA’s massive James Webb Space Telescope is only 6.5 metres in diameter.

“There was no place other than NIAC within NASA to get this off the ground,” says Walker, now an astronomy and optical engineering professor at the University of Arizona in Tucson. “At first, I was afraid to share the idea with colleagues because it sounded so crazy. You need a program within NASA that will actually look at the radical ideas, and NIAC is it.”

Parabolic dish antennas use their concave shape to capture and concentrate electromagnetic radiation. The larger the antenna’s diameter, or aperture, the more effective it is for capturing light or radio waves and transmitting radio signals over great distances.

In astronomy, there is a tremendous advantage to placing telescopes above the Earth’s atmosphere, because it tends to distort or degrade signals coming from space. The challenge is that traditional large reflector antennas are heavy, unwieldy, and difficult to stow, leading to launch constraints and risky in-space deployment schemes.

The LBR design solves both problems. Made of a thin film structure, it inflates like a beachball, providing a [lightweight] stable parabolic-dish shape without the need for bulky and complex deployable hardware, and can fold into a tiny volume.

It might be difficult to believe this all started because a young engineer’s idea of dinner one evening was what most would consider dessert. Then again, one could say the proof was in the pudding.

Meanwhile the International Space Station will be transmitting SSTV images before and after this weekend, to test some replacement hardware astronauts install on Monday and Tuesday.

Since Friday, postcards from the Service module have been transmitted, but there will be a hiatus on Monday and Tuesday to do the work. More images will be transmitted from 12 midday our time on Tuesday, until 8pm on Wednesday night, once the installation is complete, and to test the system.

The downlink frequency is 145.800 MHz, and the format will be the typical PD120 type. You should be able to receive the pictures on a handheld radio with a quarter wave whip, using normal 25KHz spaced FM. Amateurs in South Africa have been sharing their downloaded images on the HamSats whatsapp group this weekend.

This is Dave Reece, ZS1DFR, hoping you enjoyed the rugby final, no matter the outcome, and reporting for HAMNET in South Africa.