ESA-JAXA BepiColombo spacecraft separates en route to Mercury after eight-year journey
The joint ESA-JAXA BepiColombo mission is set to detach its transfer module and begin orbital insertion around Mercury, with a series of flybys and electric propulsion having taken it over six billion miles since its 2018 launch.
The BepiColombo spacecraft, a collaborative effort between the European Space Agency and Japan's aerospace agency, will separate its Mercury Transfer Module on Thursday morning, marking the next phase of its eight-year cruise toward the innermost planet. Launched on an Ariane 5 rocket from French Guiana in October 2018, the probe has traveled more than 6 billion miles using a combination of electric propulsion and nine gravity-assist flybys of Earth, Venus and Mercury.
"You can go faster to Mercury if you take a direct way to it," said Frank Budnik, flight dynamics manager for the mission at ESA. "But the problem is we want to insert into an orbit with respect to Mercury. You have to bring the spacecraft to the same velocity as Mercury has, and this is a very energy-demanding transfer."
The separation will be broadcast live by ESA, followed by a safety check at 9:53 a.m. ET. Ignacio Tanco, head of Inner Solar System Mission Operations at ESA, noted that the maneuver carries significant risk and is comparable to launching a new spacecraft around a different planet.
After the transfer module separates, the two science orbiters – ESA's Mercury Planetary Orbiter (MPO) and JAXA's Mercury Magnetospheric Orbiter (MIO) – will be captured by Mercury's gravity and enter orbit on 21 November. The orbiters will then separate from each other in early December, with MPO positioning for its science orbit on 16 December and MIO following on 10 March. Operational science activities are scheduled to begin in April.
"It will be the first time that a mission releases two fully independent, fully operational separate spacecrafts around a different planet," Tanco said.
MPO will focus on Mercury's surface, while MIO will study the planet's magnetic environment, according to mission manager Santa Martinez. Both spacecraft are equipped with solar arrays designed to limit overheating in Mercury's extreme thermal conditions, where daytime surface temperatures can reach about 430 °C.
Lead project scientist Geraint Jones said the instruments will map the planet in high resolution, investigate surface features such as the enigmatic hollows, and examine Mercury's dense composition, which may result from a massive impact that stripped away its outer crust early in solar-system history.
The mission aims to build on data from NASA's Mariner 10 and MESSENGER probes, providing new insights into Mercury's geology, magnetic field and thin exosphere.