NASA’s Perseverance rover used a microphone on its SuperCam laser instrument to listen as the Ingenuity helicopter flew for the fourth time on April 30, 2021.
“This is an example of how the different payload instrument suites complement each other, resulting in information synergy,” said Perseverance payload development manager Dr. Soren Madsen, a researcher at NASA’s Jet Propulsion Laboratory.
“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.”
With Perseverance parked 80 m (262 feet) from Ingenuity’s takeoff and landing spot, the researchers weren’t sure if the microphone would pick up any sound of the flight.
Even during flight, when the helicopter’s blades spin at 2,537 rpm, the sound is greatly muffled by the thin Martian atmosphere. It is further obscured by Martian wind gusts during the initial moments of the flight.
Listen closely, though, and the helicopter’s hum can be heard faintly above the sound of those winds.
NASA’s Ingenuity helicopter (above center to the right) is viewed by one of the hazard cameras aboard the Perseverance rover during the helicopter’s fourth flight on April 30, 2021. Image credit: NASA / JPL-Caltech.
“This is a very good surprise,” said SuperCam Mars microphone science lead Professor David Mimoun, a planetary scientist at the Institut Supérieur de l’Aéronautique et de l’Espace.
“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 scientists made the audio, which is recorded in mono, easier to hear by isolating the 84 Hz helicopter blade sound, reducing the frequencies below 80 Hz and above 90 Hz, and increasing the volume of the remaining signal.
Some frequencies were clipped to bring out the helicopter’s hum, which is loudest when the helicopter passes through the field of view of the camera.
This article is based on text provided by the National Aeronautics and Space Administration.