NASA’s Ingenuity helicopter has been making history as the first aircraft to fly on another planet, but its companion rover Perseverance has been setting records of its own as well. Perseverance was able to record audio of the Ingenuity helicopter in action, making it the first spacecraft to record the sounds of another spacecraft on another planet.
The recording was taken during Ingenuity’s fourth test flight on April 30. In the video, you can hear a low rumble caused by the wind on Mars as it blows past the rover. From that rumble comes a hum of the helicopter’s blade whipping through the thin atmosphere. After a while, the sound is distorted as the helicopter travels away from the rover before heading back, which is due to a phenomenon called the Doppler Effect.
The rover was a fair distance away from the helicopter at the time it made the recording — around 262 feet (80 meters) of distance — so it wasn’t certain that the rover’s instruments would be able to pick up any evidence of the helicopter. But by using one of its two microphones, which is part of its SuperCam instrument, Perseverance was able to record the sounds of its companion in flight.
“This is a very good surprise,” said David Mimoun, a professor of planetary science at Institut Supérieur de l’Aéronautique et de l’Espace (ISAE-SUPAERO) in Toulouse, France, and science lead for the SuperCam Mars microphone. “We had carried out tests and simulations that told us the microphone would barely pick up the sounds of the helicopter, as the Mars atmosphere damps the sound propagation strongly. We have been lucky to register the helicopter at such a distance. This recording will be a gold mine for our understanding of the Martian atmosphere.”
The sound was recorded in mono, and it was adjusted to bring out the sound of the helicopter blades at 84Hz. It was recorded using a microphone in SuperCam which works along with the instrument’s laser, which vaporizes pieces of rock to analyze their chemical composition. The microphone can help in this process by giving clues to how far into a rock the laser has penetrated, for example.
“This is an example of how the different payload instrument suites complement each other, resulting in information synergy,” said Soren Madsen, Perseverance payload development manager at NASA’s Jet Propulsion Laboratory in Southern California. “In this particular case, the microphone and video let us observe the helicopter as if we are there, and additional information, such as the Doppler shift, confirms details of the flight path.”