BepiColombo
What is BepiColombo?
Probes & telescopes· Launched 2018-10-20 – arrival 2026-11-27 planned (cruising). Europe and Japan's Mercury mission — nine flybys over seven years to brake against the Sun's pull, entering orbit in November 2026. Replay the whole spiral in the simulator.
The orbit of BepiColombo at this moment: https://nowsky.org/solar/orbit?fw=probe%3Abepicolombo&sp=2.6 — replayed live, no login.
Mission timeline
Spacecraft specs
| Launch | 2018-10-20 |
|---|---|
| Orbit insertion | 2026-11-27 (planned) |
| Flybys | Earth×1·Venus×2·Mercury×6 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When did BepiColombo launch?
- 2018-10-20.
- What is the next milestone for BepiColombo?
- 27 Nov 2026 — BepiColombo enters Mercury orbit.
- In one line, what is BepiColombo?
- Probes & telescopes — Europe and Japan's Mercury mission — nine flybys over seven years to brake against the Sun's pull, entering orbit in November 2026.
The man behind the name — who explained Mercury's 3:2 resonance
Giuseppe "Bepi" Colombo was a mathematician at the University of Padua. When radar observations in 1965 revealed Mercury's rotation period as 59 days, he was the first to point out that this locks into the 88-day orbit in an exact 3:2 resonance — until then Mercury had been assumed tidally locked 1:1 like the Moon. Three rotations for every two orbits is the product of Mercury's eccentric orbit.
In 1970 he suggested to the Mariner 10 team that if, after a Venus flyby, the spacecraft's orbital period were set to exactly twice Mercury's, it could meet Mercury three times rather than once — and Mariner 10 duly passed Mercury three times in 1974–1975. The idea of chaining gravity assists was his, so naming a spacecraft that reaches Mercury by nine of them after him was a natural choice. He died in 1984.
The mission in depth
BepiColombo is Europe and Japan's joint Mercury flotilla: an ESA planetary orbiter and a JAXA magnetospheric orbiter flying as one stack, to separate on arrival.
Reaching Mercury means braking downhill against the Sun's pull — nine flybys (Earth ×1, Venus ×2, Mercury ×6) over seven years. Its namesake, Giuseppe Colombo, pioneered exactly this kind of flyby navigation.
Orbit insertion is set for 27 November 2026. Replay the patient inward spiral in the Orbit view — the most disciplined trajectory in this simulator.
Getting to Mercury is hard not because it's far but because the Sun's gravity well keeps accelerating you — so BepiColombo must brake with flybys, nine in all: one of Earth, two of Venus, six of Mercury itself. Thruster trouble pushed arrival to late 2026, but each flyby has already returned Mercury images and magnetic-field data.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.