SCIENCE COUNTDOWNS / ESA & JAXA / BEPICOLOMBO

BepiColombo Mio Separation Countdown

Two orbiters begin to go their separate ways

After Mercury capture, BepiColombo’s two science orbiters must separate. Follow the planned release of JAXA’s Mio into its own orbit.

THE PUBLISHED MILESTONEDecember 9–10, 2026, planned Mio separation window

—MONTHS

—WEEKS

—DAYS

—HOURS

—MINUTES

To the start of ESA’s planned Mio separation window

Concept diagram of Mercury and two distinct orbital paths, illustrating Mio separation without reconstructing the navigation geometry. Concept diagram; not to scale. No measured trajectories or resolved target imagery are shown.

WHAT TO FOLLOW

Arrival is a sequence, not a single switch.

BepiColombo reaches Mercury as a combined mission, but its science orbiters have different work to do. ESA’s arrival sequence places Mercury orbit insertion on November 21, 2026, followed by the planned release of JAXA’s Mercury Magnetospheric Orbiter, Mio, on December 9–10.

The release lets Mio take its own orbit. ESA’s Mercury Planetary Orbiter continues through later steps to reach its final science orbit. The same timeline places the start of the science phase on April 6, 2027. Capture, separation and routine investigation are three different milestones.

Return for the operations team’s separation report and orbit confirmation. A timer reaching the window only tells you that the published plan has reached its date. It cannot detect a command, verify separation or show that the instruments are ready for routine science.

QUESTIONS TO RETURN FOR

Keep the evidence in view.

01 / FOLLOW THE EVIDENCE

What would confirm separation?

A dated operations report describing the release and the spacecraft’s resulting status. Keep that confirmation separate from an earlier schedule graphic.

02 / FOLLOW THE EVIDENCE

Why separate the orbiters?

Complementary orbital investigations let a mission ask different questions about Mercury. Explore the agency’s instrument and orbit explanations alongside the milestone report.

03 / FOLLOW THE EVIDENCE

When does routine science begin?

ESA’s current sequence lists April 6, 2027 for the science phase. That planned date remains subject to the preceding operations and later mission updates.

CONTINUE THE INVESTIGATION

Follow the thread.

Start with Mercury orbit insertion Follow another inner-Solar-System maneuver All science countdowns

DATE & SCIENCE SOURCES

ESA’s arrival timeline, updated July 10, 2026, lists December 9–10 for release of Mio. The clock marks December 9 at 00:00 UTC, the opening of that two-day window; no separation hour is being claimed. This is separate from November 21 Mercury orbit insertion and the planned April 6, 2027 science phase.

Source and schedule review: November 7, 2026. Check the mission or observing source for later changes. A clock reaching zero does not confirm an outcome.

Remind me to check the outcome

Choose your calendar

Return for reports on December 12, 2026 at 9:00 a.m. in your calendar’s time zone, two days after the event day or window ends.

Google Calendar Apple Calendar Microsoft Outlook

This is a return-for-results reminder, not the event time or an observing alarm. Check the date, time and alert before saving. Reports may take longer.

Saved reminders do not update if the schedule changes. Remove the old reminder and add a new one from this page.

Need another way?

Download the calendar file (.ics) and open it in your calendar. For Outlook on the web, choose Add calendar → Upload from file. For Google Calendar on a computer, choose Settings → Import & export → Import.

No email signup. We don’t receive your calendar details.