BepiColombo 3rd Mercury flyby June 19, 2023
BepiColombo will make its 3rd flyby of the planet Mercury on June 19, 2023. The spacecraft will sweep closest to Mercury at 19:34 UTC (2:34 p.m. CDT) that day. Images to come soon!
BepiColombo is a joint Mercury mission, launched in October 2018 by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA). For the past several years, our sun’s inner planets have been giving BepiColombo gravity assists, needed to enable the spacecraft to achieve a stable orbit around Mercury.
BepiColombo is due to enter Mercury’s orbit on December 5, 2025. In the meantime, there will be three more flybys after Monday’s close approach.
Why the gravity assists?
Why can’t BepiColombo just shoot on over to Mercury and go into orbit around it? It can’t, because Mercury is so near the sun.
The flyby maneuvers will keep the craft from being pulled into the sun’s gravity well. With one Earth flyby, two Venus flybys, and six eventual Mercury flybys, the spacecraft will lose enough energy that Mercury will capture it in its orbit. That’s right, we said “lose.” We typically think of a gravity assist as a way to boost a spacecraft’s energy. But a gravity assist can either speed up or slow down a spacecraft. Or it can simply change a craft’s direction.
ESA flight dynamics expert Frank Budnik explained more about this 3rd flyby:
As BepiColombo starts feeling Mercury’s gravitational pull, it will be traveling at 3.6 km/s with respect to the planet. That’s just over half the speed it approached with during the previous two Mercury flybys.
And this is exactly what the point of such events is. Our spacecraft began with far too much energy because it launched from Earth and, like our planet, is orbiting the sun. To be captured by Mercury, we need to slow down, and we’re using the gravity of Earth, Venus and Mercury to do just that.
