Ham Radio Signals from Mars

Feb. 16, 2021: Around the world, ham radio operators are doing something once reserved for national Deep Space Networks. “We’re monitoring spacecraft around Mars,” says Scott Tilley, of Roberts Creek, British Columbia, who listened to China’s Tianwen-1 probe go into orbit on Feb. 10th. The signal, which Tilley picked up in his own back yard, was “loud and audible.”  Click to listen:

The signal from Tianwen-1 is dominated by a strong X-band carrier wave with weaker side bands containing the spacecraft’s state vector (position and velocity). Finding this narrow spike of information among all the possible frequencies of deep space communication was no easy task.

“It was a bit like a treasure hunt,” Tilley says. “Normally a mission like this would have its frequency published by the ITU (International Telecommunications Union). China did make a posting, but it was too vague for precise tuning. After Tianwen-1 was launched, observers scanned through 50MHz of spectrum and found the signal. Amateurs have tracked the mission ever since with great accuracy thanks to the decoded state vector from the probe itself.”

So far, Tilley has picked up signals from China’s Tianwen-1 spacecraft, NASA’s Mars Reconnaissance Orbiter, and the United Arab Emirates’ Hope probe–all orbiting Mars approximately 200 million kilometers away. How is such extreme DX’ing possible?

“It helps to have a big antenna,” says Tilley, who uses a 60 cm dish, pictured above. “But the real key,” he says, “is the advent of Software Defined Radios (SDRs) , which have become the norm for hams in the past decade or so.”

In a Software Defined Radio, computers digitally perform the signal mixing and amplification functions of circuits that used to be analog. SDRs are cheap, sensitive, and they give hams the kind of exquisite control over frequency required to tune into distant spacecraft.

“Amateurs really began listening to deep space probes in the late 1990s and early 2000s,” says Tilley. “This sparked an awareness that it was possible. The combination of improving technology and growing awareness has resulted in more and more interplanetary detections.”

Next up: NASA’s Mars 2020 spacecraft carrying the Perseverance rover, due to reach Mars Feb. 18th:

Tilley plans to listen but he doesn’t expect a strong signal. “Perseverance does not have a very large antenna,” says Tilley. “It doesn’t need one because it can use other NASA spacecraft in Mars orbit as relays. The signal will therefore be weak and I doubt many amateurs will record the landing in Jezero crater.”

Tianwen-1, on the other hand, has a relatively large antenna with a booming signal. “China probably plans to use it as a relay for future Chinese space missions,” Tilley speculates. “This makes it a good target for hams hoping to bag their first Martian spacecraft.”

Stay tuned for more radio signals from Mars.

A New Form of Space Weather: Earth Wind

Feb. 12, 2021: The sun is windy. Every day, 24/7, a breeze of electrified gas blows away from the sun faster than a million mph. Solar wind sparks beautiful auroras around the poles of Earth, sculpts the tails of comets, and scours the surface of the Moon.

Would you believe, Earth is windy, too? Our own planet produces a breeze of electrified gas. It’s like the solar wind, only different, and it may have important implications for space weather on the Moon.

“Earth wind” comes from the axes of our planet. Every day, 24/7, fountains of gas shoot into space from the poles. The leakage is tiny compared to Earth’s total atmosphere, but it is enough to fill the magnetosphere with a riot of rapidly blowing charged particles. Ingredients include ionized hydrogen, helium, oxygen and nitrogen.

Once a month, the Moon gets hit by a blast of Earth wind. It happens around the time of the full Moon when Earth’s magnetic tail points like a shotgun toward the lunar disk. For 3 to 5 days, lunar terrain is bombarded by H+, He+, O+, N2+ and other particles.

One effect of Earth wind, just discovered, is to create water. According to a new study published in the January 2021 edition of the Astrophysical Journal Letters, Earth wind can actually make H2O on the lunar surface.

“Hydrogen ions in Earth wind combine with oxygen in Moon rocks and soil to make hydroxyl (OH) and water (H2O),” explains one of the lead authors, Quanqi Shi of Shandong University and the Chinese Academy of Sciences. “This came as a surprise.”

Above: An artist’s concept of Earth wind (blue)

Researchers have long known that hydrogen from space raining down on the Moon can create a temporary form of surface water. Solar wind does it all the time. However, this kind of water was expected to dry up once a month when the Moon enters Earth’s magnetic tail. Terrestrial magnetism deflects solar wind, turning the faucet to the OFF position.

But that’s not what happened.

The researchers looked at data from NASA’s Moon Mineralogy Mapper (M3) onboard India’s Chandrayaan-1 spacecraft, which was orbiting the Moon in 2009 when the Moon made multiple passes through Earth’s magnetic tail.  “We found that lunar surface water does not disappear as expected during the magnetosphere shielding period,” says Shi. “Earth wind must be bridging the gap.”

Above: Sample Chandrayaan-1 observations of lunar surface water [more]

In fact, when it comes to producing water, Earth wind has some big advantages over solar wind. When the full Moon is inside Earth’s magnetic tail, it is surrounded by Earth wind and feels its impact from every direction. The lunar nearside, lunar farside, and lunar poles are all peppered with Earth wind particles. In this sense, Earth wind can potentially make water anywhere–unlike the solar wind which rains down only on the lunar dayside.

Another potential advantage of Earth wind: It is oxygen rich, much more so than solar wind. “Oxygen is another key element of water,” points out Shi. “Whether these oxygen ions can contribute to the formation of lunar water is a very intriguing question for future study.”

Want to learn more? Read the original research here: “Earth Wind as a Possible Exogenous Source of Lunar Surface Hydration

Co-rotating Interaction Region Sparks Auroras

Feb. 3, 2021: What made the auroras of Feb. 2nd so good? It was a co-rotating interaction region (CIR). CIRs are transition zones between slow- and fast-moving streams of solar wind. Solar wind plasma piles up in these regions, creating density gradients and shock waves that can rock Earth’s magnetic field much like a coronal mass ejection (CME).

A CIR hit Earth on Feb. 2nd and “the lights were incredible–just fantastic,” reports aurora tour guide Marianne Bergli who witnessed the display from a beach near Tromsø, Norway:

“Every color in the heavens cycled through the sky,” she says. “It. Was. Amazing.”

CIRs are a way for the sun to spark auroras without explosive solar activity. All that’s required is a fast solar wind stream brushing up against a slower one. In the transition zone, thick rivulets of plasma press magnetic fields together, creating strong shock-like structures that mimic CMEs. Indeed, some forecasters refer to co-rotating interaction regions as “mini-CMEs.”

Says Bergli, “I am looking forward to the next one!”