LoRa to the Moon and back: Messages bounced off lunar surface using off-the-shelf hardware

... and a damn big radio telescope


A team of scientists has managed to bounce a LoRa message off the Moon, setting an impressive record of 730,360km for the furthest distance such a data message has travelled.

While much of the technology was off-the-shelf (Semtech's LR1110 RF transceiver chip was used) the signal was amplified to 350w using the 25-metre dish of the Dwingeloo Radio Observatory in the Netherlands. The same dish and chip was used to receive the signal on its return from the Moon, just under two and a half seconds later.

The team consisted of Thomas Telkamp, CTO of Lacuna Space and Frank Zeppenfeldt, a 20-year ESA veteran working in the field of IoT and Smallsats. For CAMRAS (CA Muller Radio Astronomy Station), the foundation behind the telescope, were Jan van Muijlwijk and Tammo Jan Dijkema.

The Register spoke to Telkamp, who told us the project "was a thing that was on my to do list for a long time."

"We figured out 'We should be able to do this'," he added, "and then it was a matter of finding all the equipment and people to execute it".

"And, ultimately, we needed a big telescope."

Although bouncing signals off the Moon is hardly a new thing (and reflectors left on the lunar surface by the Apollo and Lunokhod programs have enabled scientists to use laser ranging to get a precise measurement of the distance between the Earth and Moon) doing it with LoRa and off-the-shelf components: "was really the challenge," said Telkamp.

"And because we only had one telescope available it needed to be a very short message," he told us, "because we needed to receive our own message.

"So we transmit, immediately switch to the receive mode and receive our own message back. And that is for me the most hilarious part of it... this whole message for a short term of time is actually in space as a whole. At some point you have transmitted the message, you're going to receive it so you're waiting for your own message to be bounced back to you."

As well as the technology demonstration of actually bouncing a message off the Moon, some bonus science was accomplished during the experiment. "Because the radio signals were slightly shifted," Telkamp explained, "and we could compare them to the theoretical position of the Moon."

The Moon, of course, moved during the transmission of the message.

"And with that," he added, "we basically could make a radar image of the Moon, which was completely not the purpose of the whole experiment but just as a side effect.

"We could actually see the sphere of the Moon simply by looking at the message that was echoed back to us."

The experiment is undoubtedly neat. (Nicolas Sornin, co-inventor of LoRa, gave it a thumbs-up, declaring himself impressed with the quality of the data, and said: "This is a fantastic experiment. I had never dreamed that one day a LoRa message would travel all the way to the Moon and back.") The practical applications, meanwhile, are of interest to space agencies.

"This is not 5G, high bandwidth stuff," Telkamp told us, "this is low bandwidth stuff, but also low power, low cost and very very small."

So think more messaging from an astronaut or telemetry from a probe than full-on high definition video.

As for next steps, getting an additional radio telescope would save having to quickly reconfigure a single dish from transmit to receive. And perhaps farther afield? "It would be nice to do this with Venus," Telkamp mused, before laughing: "But that's a few orders of magnitude more difficult." ®

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