ESA/JAXA Listen to the BEPICOLOMBO SPACECRAFT as it flies past Mercury on 8 January 2025. This sixth and final flyby used the little planet’s gravity to propel the spacecraft to enter orbit around Mercury in 2026.
What you can hear in the Sonification soundtrack of this video are actual spacecraft vibrations measured by the Italian Spring Accelerometer (ISA) instrument. The accelerometer data is frequency shifted to make it audible to human ears – one hour’s measurements are spread out to one minute of sound.
The Bepicolombo is stirring ever so slightly: the fuel is sizzling a little, the solar panels are vibrating at their natural frequency, the heat pipes are pushing vapor through tiny tubes, and so forth. This creates a horrible underlying HUM throughout the video.
But as Beicolombo gets closer to Mercury, the ISA detects other forces at work on the spacecraft. The most scientifically interesting are the audible shocks that sound like small, soft bongs. These respond to spacecraft entering and exiting Mercury’s shadow, where the Sun’s intense radiation is suddenly blocked. One of the ISA’s scientific goals is to monitor changes in ‘solar radiation pressure’ – a force caused by sunlight as it orbits the Sun and, ultimately, Mercury.
The loudest noise – an ominous ‘rumbling’ – is caused by the rotation of the spacecraft’s large solar panels. The first rotation occurs in the shadows at 00:17 in the video, while the second adjustment at 00:51 was also captured by one of the spacecraft’s surveillance cameras.
The wind being picked up in the phone call becomes more audible around 30 seconds into the video, which is caused by Mercury’s gravitational field pulling on the nearest and farthest parts of the spacecraft by different amounts. As the planet’s gravity stretches the spacecraft ever so slightly, the spacecraft responds structurally. At the same time, the onboard reaction wheels change their speed to maintain the spacecraft’s orientation, which you can hear as a frequency shift in the background.
This is the last time that many of these effects can be measured with Bepicolombo’s largest solar panels, which make the spacecraft susceptible to vibrations. The spacecraft module carrying these panels will not enter orbit around Mercury with the mission’s two orbiter spacecraft.
The video shows an accurate simulation of the spacecraft and its path past Mercury during the flyby, created with the SPICE-enhanced Cosmographia spacecraft visualization tool. The inset appearing 38 seconds into the video shows actual photographs taken by one of Bepicolombo’s monitoring cameras.
Read more about Bepicolombo’s sixth Mercury flyby
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