BepiColombo Earth-Venus-Mercury gravity-assist cruise, SPK-derived V_inf

bepicolombo-earth-venus-mercury · source: literature · validation: V0

Signature

Bodies: E-E-V-V-Me-Me-Me-Me-Me-Me
Primary: Sun (default — heliocentric)
Sequence (canonical): E-E-V-V-Me-Me-Me-Me-Me-Me
Sense: n/a
Orbit class: Tour
MGA tour (one-shot terminal arrival)
Cycler class: multi-arc
Returns: 1 — finite for epoch-locked classes
Validity window: 2018-10-20 → 2025-01-08
Launch epoch: 2018-10-20T01:45:00Z
Trajectory regime: ballistic
Maintenance ΔV band: unclassified
Model assumption: analytic-ephemeris
Mid-fidelity: real eccentricity / inclination retained; not full N-body.
Period: not strictly periodic (no published period)
Source ephemeris: DE440 + ESA SPICE Service reconstructed BepiColombo MPO SPK (bc_mpo_fcp_00226_20181020_20270407_v01.bsp, NAIF -121)
Ephemeris model the source states its numbers were computed against.
Priority date: 2018-10-20

V∞ at encounters

E (encounter 1): 3.99 km/s
Earth gravity-assist flyby 2020-04-10T04:25 UTC; vis-viva std 0.003 km/s; CA 12,686 km alt vs published 12,677 km (ESA) +0.07%. (bc_mpo_fcp_00226, NAIF -121).
V (encounter 2): 7.98 km/s
Venus-1 flyby 2020-10-15T03:58 UTC; vis-viva std 0.007 km/s; CA 10,722 km alt vs published 10,720 km (ESA) +0.02%.
V (encounter 3): 8.02 km/s
Venus-2 flyby 2021-08-10T13:51 UTC; vis-viva std 0.007 km/s; CA 553 km alt vs published ~552 km (ESA) +0.10%.
Me (encounter 4): 6.66 km/s
Mercury-1 flyby 2021-10-01T23:35 UTC; vis-viva std 0.010 km/s; CA 199 km alt vs published 199 km (ESA) -0.10%.
Me (encounter 5): 6.42 km/s
Mercury-2 flyby 2022-06-23T09:44 UTC; vis-viva std 0.026 km/s; CA 198 km alt vs published 200 km (ESA) -0.97%.
Me (encounter 6): 3.64 km/s
Mercury-3 flyby 2023-06-19T19:34 UTC; vis-viva std 0.017 km/s; CA 235 km alt vs published 236 km (ESA) -0.51%.
Me (encounter 7): 2.75 km/s
Mercury-4 flyby 2024-09-04T21:48 UTC; vis-viva std 0.014 km/s; CA 163 km alt vs published 165 km (ESA) -1.01%.
Me (encounter 8): 2.61 km/s
Mercury-5 flyby 2024-12-01T14:23 UTC; vis-viva std 0.013 km/s; CA 37,626 km alt vs published 37,626 km (ESA) -0.00%. This is the deliberately HIGH post-anomaly flyby (Sept 2024 solar-electric-thruster power shortfall raised the targeted altitude from ~37 km to 37,626 km) -- a genuine gravity assist, not the terminal capture.
Me (encounter 9): 1.89 km/s
Mercury-6 flyby 2025-01-08T05:59 UTC; vis-viva std 0.010 km/s; CA 295 km alt vs published 295 km (ESA) +0.00%; the final pre-capture flyby.

Cycle-level identity (multi-arc invariants)

Aphelion ratio (AR): —
Turn ratio (TR): —
Transit times (days): —

Orbit view 2.5D ecliptic projection

spacecraft: analytic-ephemeris (real e/i retained) planets: J2000 osculating ellipse (Standish & Williams Table 1) orientation: coplanar-idealized (no Ω/ω published — in-plane ellipse)

3D view not available for multi-arc trajectories yet. The 3D system can now render a numerically-sampled polyline (n-body or multi-arc), but no sampled trajectory is published for this row — each leg is a separate ellipse with honest gaps where elements are unpublished (the 2D view above shows them). The button will appear here once a sampled path is exported for this trajectory; we never interpolate one from the catalogue's per-leg (a, e).

— — planet orbit (true J2000 ellipse)

Flyby altitudes (minimal-thrust)

Per-flyby periapsis altitude that delivers each encounter's required turn ballistically, capped at the body's safe flyby floor (200 km for Earth/Mars). A flyby sitting at the floor is bend-binding (it needs the deepest safe pass); higher altitudes are gentler flybys that need less turn. · source: derived

Node	Body	Altitude (km)
0	E	12,677
1	V	10,720
2	V	552
3	Me	200
4	Me	236
5	Me	295

Definition status

incomplete — core fields missing or known-unknowns tracked below

Primary citation

ESA BepiColombo (2025). BepiColombo mission / Earth-Venus-Mercury gravity-assist flyby parameters. ESA Science (cosmos.esa.int/web/bepicolombo-flyby) + ESA per-flyby press releases.

orbit source derived orbit fidelity real-de440 V∞ source derived V∞ fidelity real-de440

Corroborating sources

ESA SPICE Service (2025). BepiColombo SPICE Kernel Dataset (reconstructed MPO SPK). spiftp.esac.esa.int/data/SPICE/BEPICOLOMBO/.
Provenance of the reconstructed BepiColombo MPO spacecraft SPK (bc_mpo_fcp_00226_20181020_20270407_v01.bsp) that the vinf_at_flyby reads; the per-flyby V_inf is DERIVED from this authoritative mission kernel.

Notes

BepiColombo's flown Earth-Venus-Mercury gravity-assist cruise to Mercury -- the most flyby-rich gravity-assist tour ever flown: 1 Earth + 2 Venus + 6 Mercury gravity assists (a solar-electric-propulsion-assisted MGA tour), spiralling into Mercury capture (MOI). The per-flyby V_inf is not published in clean form, so we derive it from the ESA SPICE Service reconstructed MPO spacecraft SPK at the sourced flyby epochs (cyclerfinder.verify.mission_spk.vinf_at_flyby). The kernel is the ESA reconstructed flight-dynamics product bc_mpo_fcp_00226 (61 MB, NAIF -121, one continuous segment 2018-2027) -- the coarse bc_mmo_scp_cruise kernel (7 KB) is unusable. Recon: docs/notes/2026-06-19-bepicolombo-kernel-recon.md. All 9 gravity-assist flybys extracted cleanly (every periapsis refined, every vis-viva V_inf converged to <=0.027 km/s std), with CA altitudes reproducing the published ESA values to <=1.01% (Mercury-4 the max; all others <1%). V_inf decreases monotonically 8.02 km/s (Venus-2) -> 1.89 km/s (Mercury-6) as the spacecraft brakes into the Mercury-resonant approach. Mercury-5 is the deliberately HIGH (37,626 km) post-anomaly flyby (Sept 2024 thruster power shortfall) -- a real gravity assist correctly extracted, not an artefact. Earth departure (2018-10-20) and the terminal Mercury Orbit Insertion (delayed to Nov 2026 following the 2024 thruster anomaly) carry no V_inf entry: the launch C3 is not assigned a fabricated departure V_inf, and MOI is a capture, not a hyperbolic flyby (the symmetric vis-viva extraction does not apply to a capture). Sourced-only discipline. validity_window.end is the last SPK-derived gravity-assist flyby (Mercury-6, 2025-01-08). validation_level=V0 (orbit_source = vinf_source = derived -> 'unvalidated' provenance tier; V0 on validation_level), even though every CA altitude reproduces the published ESA record to <=1.01%. The 9th SPK-derived mga_tour row -- and the one that closes the classic-mission backlog (Mariner 6/7 excluded as pre-gravity-assist-era direct flybys; out of scope). See docs/notes/2026-06-19-bepicolombo-kernel-recon.md and docs/notes/2026-06-19-390-spk-vinf-extractor.md.

Source quotes (per-field provenance)

Every numerical value in this entry traces to a verbatim or paraphrased quote from a cited source.

launch_epoch: BepiColombo launched 2018-10-20 01:45 UTC on an Ariane 5 ECA (flight VA245) from Kourou (ESA).
validity_window.end: Mercury-6 flyby 2025-01-08T05:59 UTC, the last SPK-derived gravity-assist flyby before Mercury Orbit Insertion (MOI delayed to Nov 2026 after the 2024 thruster anomaly).
vinf_kms_at_encounters.0.vinf_kms: DERIVED: planetocentric V_inf 3.993 km/s from ESA SPK bc_mpo_fcp_00226_20181020_20270407_v01.bsp (BepiColombo MPO, body -121) at the Earth gravity-assist CA 2020-04-10T04:25 UTC; CA 12,686 km alt reproduces the published 12,677 km (ESA) to +0.07%.
vinf_kms_at_encounters.8.vinf_kms: DERIVED: planetocentric V_inf 1.892 km/s at the Mercury-6 CA 2025-01-08T05:59 UTC; CA 295 km alt reproduces the published 295 km (ESA) to +0.00%; the final pre-capture flyby.
n_returns: Single Earth launch (2018-10-20) and single Mercury arrival (MOI 2026); n_returns=1 per the v4.7 mga_tour invariant (no continuing tour at Earth).