Voyager 2 Grand Tour E-J-S-U-N (MJS77/JSX), SPK-derived V_inf

voyager-2-grand-tour · source: literature · validation: V0

Signature

Bodies: E-J-S-U-N
Primary: Sun (default — heliocentric)
Sequence (canonical): E-J-S-U-N
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: 1977-08-20 → 1989-08-25
Launch epoch: 1977-08-20T14:29:00Z
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 + NAIF reconstructed Voyager 2 spacecraft SPK (vgr2_jup230.bsp, vgr2_sat337.bsp, vgr2.ura182.bsp, vgr2_nep097.bsp; + P-A)
Ephemeris model the source states its numbers were computed against.
Priority date: 1977-08-20

V∞ at encounters

J (encounter 1): 7.64 km/s
SPK-derived planetocentric V_inf at Jupiter closest approach 1979-07-09T22:29 UTC (vgr2_jup230.bsp, NAIF -32); vis-viva outer-window std 0.031 km/s; CA 10.09 R_J vs published 10.0 R_J (Kohlhase-Penzo 1977 Table IV JSX).
S (encounter 2): 10.67 km/s
SPK-derived planetocentric V_inf at Saturn closest approach 1981-08-26T03:24 UTC (vgr2_sat337.bsp, NAIF -32); vis-viva outer-window std 0.001 km/s; CA 2.68 R_S.
U (encounter 3): 14.73 km/s
SPK-derived planetocentric V_inf at Uranus closest approach 1986-01-24T17:58 UTC (vgr2.ura182.bsp, NAIF -32); vis-viva outer-window std 8e-6 km/s; CA 4.19 R_U / 81,573 km alt vs published 81,500 km above cloud tops (Wikipedia 'Voyager 2'; NASA '35 Years Ago: Voyager 2 Explores Uranus' 50,700 mi). P-A.
N (encounter 4): 16.74 km/s
SPK-derived planetocentric V_inf at Neptune closest approach 1989-08-25T03:56 UTC (vgr2_nep097.bsp, NAIF -32); vis-viva outer-window std 4e-4 km/s; CA 1.18 R_N / 29,271 km radius-from-center vs published ~29,240 km (4,950 km above the north pole, Wikipedia 'Voyager 2'). P-A.

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	J	650,060
1	S	101,050
2	U	81,573
3	N	4,507

Definition status

incomplete — core fields missing or known-unknowns tracked below

Primary citation

Kohlhase, C. E. & Penzo, P. A. (1977). Voyager Mission Description. Space Science Reviews 21(2):77-101.

DOI: 10.1007/bf00200846

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

Corroborating sources

Acton, C. H. (1996). Ancillary data services of NASA's Navigation and Ancillary Information Facility (NAIF SPICE). Planetary and Space Science 44(1):65-70. DOI: 10.1016/0032-0633(95)00107-7
Provenance of the reconstructed spacecraft SPK kernels (vgr2_jup230.bsp, vgr2_sat337.bsp, vgr2.ura182.bsp, vgr2_nep097.bsp) from the NAIF public archive that the vinf_at_flyby reads; the four-planet V_inf tuple is DERIVED from these authoritative mission kernels.

Notes

Voyager 2's flown outer-planet Grand Tour: the ONLY spacecraft to visit all four giant planets (Jupiter, Saturn, Uranus, Neptune), made possible by the once-per-176-yr four-giant-planet alignment. The catalogue's first four-giant-planet Grand Tour row, and (with voyager-1-jupiter-saturn-grand- tour) one of the catalogue's first SPK-derived mga_tour rows. As with Voyager 1, the per-encounter V_inf is not published in clean form in any Voyager mission-overview or dedicated-navigation paper (firm negative); we derive it directly from the mission's archived NAIF reconstructed spacecraft SPK at the already-sourced flyby epochs (cyclerfinder.verify.mission_spk.vinf_at_flyby). The Jupiter + Saturn encounters were extracted in; Uranus + Neptune in the admission follow-on (P-A) with the same code, zero new code. Encounters (data/390_mission_vinf.jsonl), each cross-checked against the published closest-approach geometry (the sourced, independent EXPECTED side): * Jupiter 1979-07-09T22:29 UTC: V_inf 7.639 km/s, CA 10.09 R_J (vs published 10.0 R_J, Kohlhase-Penzo Table IV JSX; <1%). * Saturn 1981-08-26T03:24 UTC: V_inf 10.674 km/s, CA 2.68 R_S. * Uranus 1986-01-24T17:58 UTC: V_inf 14.732 km/s, CA 4.19 R_U / 81,573 km alt (vs published 81,500 km above cloud tops; <0.1%). * Neptune 1989-08-25T03:56 UTC: V_inf 16.742 km/s, CA 1.18 R_N / 29,271 km radius-from-center (vs published ~29,240 km / 4,950 km above the north pole; <0.2%). Earth departure (1977-08-20) carries no V_inf entry (no clean published launch C3 / departure V_inf in the acquired literature; the extractor reads the planetocentric flyby V_inf only). Sourced-only discipline. validation_level=V0 on the same orthogonal-axis convention as Voyager 1: derived/derived -> 'unvalidated' on the provenance-tag tier axis, V0 on the validation_level axis, even though the closest-approach geometry reproduces the published mission record to <0.2%. Admitted as the payoff (parent-reviewed). See 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: Voyager 2 launched 1977-08-20 14:29 UTC (Kohlhase-Penzo 1977 'Voyager Mission Description'; NASA Voyager fact pages).
validity_window.start: Same as launch_epoch (Voyager 2 launch 1977-08-20).
validity_window.end: Neptune closest approach 1989-08-25T03:56 UTC, the last SPK-derived encounter (data/390_mission_vinf.jsonl; CA confirmed by fine periapsis scan, 29,271 km from center).
vinf_kms_at_encounters.0.vinf_kms: DERIVED: planetocentric V_inf 7.639 km/s from NAIF SPK vgr2_jup230.bsp (Voyager 2, body -32) at Jupiter closest approach 1979-07-09T22:29 UTC; vis-viva converged outside Jupiter SOI (outer-window std 0.031 km/s). CA radius 10.09 R_J independently reproduces Kohlhase-Penzo 1977 Table IV (10.0 R_J).
vinf_kms_at_encounters.1.vinf_kms: DERIVED: planetocentric V_inf 10.674 km/s from NAIF SPK vgr2_sat337.bsp (Voyager 2, body -32) at Saturn closest approach 1981-08-26T03:24 UTC (outer-window std 0.001 km/s).
vinf_kms_at_encounters.2.vinf_kms: DERIVED (P-A): planetocentric V_inf 14.732 km/s from NAIF SPK vgr2.ura182.bsp (Voyager 2, body -32) at Uranus closest approach 1986-01-24T17:58 UTC (outer-window std 8e-6 km/s); CA 4.19 R_U / 81,573 km alt reproduces the published 81,500 km above cloud tops (Wikipedia 'Voyager 2'; NASA '35 Years Ago: Voyager 2 Explores Uranus', 50,700 mi) to <0.1%.
vinf_kms_at_encounters.3.vinf_kms: DERIVED (P-A): planetocentric V_inf 16.742 km/s from NAIF SPK vgr2_nep097.bsp (Voyager 2, body -32) at Neptune closest approach 1989-08-25T03:56 UTC (outer-window std 4e-4 km/s); CA 1.18 R_N / 29,271 km radius-from-center reproduces the published ~29,240 km (4,950 km above the north pole, Wikipedia 'Voyager 2') to <0.2%.
n_returns: Single Earth launch (1977-08-20) and single Neptune departure (1989-08-25); n_returns=1 per the v4.7 mga_tour invariant (no continuing tour at Earth).