The moon has captured the imagination of the human race since prehistoric times, a universal icon of unreachable places. So when we were offered the opportunity to send the first Chirp transmission to the moon, we couldn't say no.
We met artist Martine-Nicole Rojina at the Abbey Road Hackathon last year, whose practice has led to a close-knit art-science-innovation partnership with the Dwingeloo Radio Observatory, Netherlands. Her project Sister Moon harnesses the 25m Dwingeloo radio telescope to beam audio messages to the moon, encoded as radio-frequency signals. When the RF transmission strikes the moon's surface, it bounces back and – just 2.5 seconds later – returns to earth and can be demodulated back to audio, conditioned by the noise and static of its interplanetary travel.
Martine-Nicole suggested that we may be able to use the channel to transmit a short Chirp signal. We were, to put it mildly, enthusiastic about the proposition. After a short discussion with Harry Keizer and Jan van Muijlwijk via video link to the observatory, we swiftly prototyped a Chirp transmission protocol bespoke to the channel's requirements; that is to say, low acoustic bandwidth, high noise.
Because we were connected via a standard Skype link, the Chirp transmission needed to pass through the following signal chain:
→ LAPTOP SPEAKER
→ SKYPE VOIP
→ RF MODULATION
And on the return leg:
→ RF DEMODULATION
→ SKYPE VOIP
→ LAPTOP MICROPHONE
→ CHIRP DECODER
We have liftoff
Finally, with much trepidation, we lined up the Chirp command-line toolkit to begin the relay – and hit send. 🚀 The signal was heard from the computer speaker, followed by a moment's delay as it was beamed from the radio telescope and upwards through the earth's atmosphere. The moon-bounced response then crackled back through the Skype link, backed with cosmic static.
Astonishingly, given the number of lossy links in the transmission pipeline, the transmission decoded first time. The message:
Hear the transmission:
And there it was. A chirp signal, decoded intact after a 768,800km round-trip to the moon and back. It's an awesome testament to the technology's resilience, and an undeniably magical feeling to hear a signal that has returned from the surface of the moon.
Many thanks to Martine-Nicole, and all of the team at Dwingeloo.
- Artist Martine-Nicole Rojina, and her project Sister Moon
- Dwingeloo Radio Telescope on Twitter: @radiotelescoop