BepiColombo sheds its propulsion module as ESA confirms a signal from Mercury's approaching orbiters
The European Space Agency and Japan's space agency separated BepiColombo's propulsion module from its two Mercury-bound science orbiters on 3 September, the first step of an eight-year mission's arrival sequence. ESA's mission control detected a preliminary Doppler signal consistent with the planned manoeuvre and streamed the operation live from Darmstadt. Mercury orbit capture follows on 21 November, with science operations set to begin in April 2027.
Science··Evening
Mercury arrival phase begins with a scheduled separation
The European Space Agency and Japan's space agency separated BepiColombo's Mercury Transfer Module from its two Mercury-bound science orbiters on 3 September, the opening step of the mission's arrival sequence after an eight-year journey and nine planetary flybys. ESA reported it expected to reacquire signals from the released orbiters no earlier than 13:53 GMT and broadcast the operation live from its control centre in Darmstadt. Once free of the transfer module, the orbiters travel on as a linked pair on a free-falling trajectory, correcting course only with the orbiter's own chemical thrusters. Europe's Mercury Planetary Orbiter and Japan's Mio remain locked together until they separate from each other in December, with Mio set for an elongated final orbit reaching from 590 kilometres to 11,640 kilometres above the planet.[1], [2]
Eight years and nine flybys to reach the inner solar system
BepiColombo launched in October 2018 and reached Mercury by a looping route through the inner solar system rather than a direct trajectory, using nine planetary flybys along the way to shed enough orbital energy to be captured by the Sun's closest planet. The mission is the first to place two science orbiters around Mercury at once, Europe's Mercury Planetary Orbiter and Japan's Mio. Space.com reported that the 3 September separation was the first move of a longer arrival sequence, with Mercury orbit capture scheduled for 21 November, release of Mio in December, and the start of science operations targeted for April 2027, when researchers can begin returning data from both spacecraft together.[1]
ESA tracks a preliminary signal through the separation window
ESA's live mission updates showed its Mission Control Team clearing the spacecraft for separation at 11:03 BST after completing a full roll call, then starting its public livestream at 12:45 BST. By around 13:00 BST the transfer module was expected to have separated, and at 13:41 BST ESA reported a preliminary Doppler signal, a shift in the radio frequency exchanged between Earth and the spacecraft, consistent with the planned separation sequence. Full confirmation was expected from the Mercury Planetary Orbiter itself no earlier than 14:53 BST. ESA ran the entire sequence from its Darmstadt control centre as one of the most operationally demanding phases the agency has attempted in a planetary mission.[2]
