Voyager 1 Jupiter-Saturn gravity-assist tour (MJS77 JST), SPK-derived V_inf

voyager-1-jupiter-saturn-grand-tour · source: literature · validation: V0

Signature

Bodies: E-J-S
Primary: Sun (default — heliocentric)
Sequence (canonical): E-J-S
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: 1977-09-05 → 1980-11-12
Launch epoch: 1977-09-05T12:56:00Z
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 1 spacecraft SPK (vgr1_jup230.bsp, vgr1_sat337.bsp)
Ephemeris model the source states its numbers were computed against.
Priority date: 1977-09-05

V∞ at encounters

J (encounter 1): 10.77 km/s
SPK-derived planetocentric V_inf at Jupiter closest approach 1979-03-05T12:05 UTC (vgr1_jup230.bsp, NAIF -31); vis-viva outer-window std 0.006 km/s; CA 4.88 R_J vs published 4.89 R_J (Kohlhase-Penzo 1977 Table IV JST).
S (encounter 2): 15.17 km/s
SPK-derived planetocentric V_inf at Saturn closest approach 1980-11-12T23:46 UTC (vgr1_sat337.bsp, NAIF -31); vis-viva outer-window std 0.030 km/s; CA 3.06 R_S (high-energy Titan-targeted approach).

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no sampled trajectory is published for this row — each leg is a separate ellipse with honest gaps where elements are unpublished (the 2D view above shows them).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	277,369
1	S	123,875

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 (vgr1_jup230.bsp, vgr1_sat337.bsp) from the NAIF public archive that the vinf_at_flyby reads; the V_inf is DERIVED from these authoritative mission kernels.

Notes

Voyager 1's flown Jupiter-Saturn gravity-assist tour (MJS77, the JST high-energy Titan-targeted branch). The catalogue's first SPK-DERIVED mga_tour row: the per-encounter hyperbolic-excess velocity (V_inf) is not published in clean form in any Voyager mission-overview or dedicated- navigation paper (firm negative, including the best-case venue McKinley-Van Allen 1976) -- the true V_inf live in unobtainable internal JPL documents. instead DERIVES the V_inf directly from the mission's archived NAIF reconstructed spacecraft SPK at the already-sourced flyby epochs (cyclerfinder.verify.mission_spk.vinf_at_flyby): furnsh DE440 + LSK + the spacecraft SPK, sample the planetocentric state over a window around closest approach, and read the vis-viva hyperbolic-excess speed sqrt(v_rel^2 - 2*mu/r_rel) at the outermost sample where v_rel -> V_inf. Encounters (data/390_mission_vinf.jsonl): * Jupiter 1979-03-05T12:05 UTC: V_inf 10.773 km/s, CA 4.88 R_J / 277,369 km alt. CA radius reproduces the published 4.89 R_J (Kohlhase-Penzo Table IV) to <0.2% -- the independent, sourced cross-check (the EXPECTED side of the geometry check is published, not computed by us). * Saturn 1980-11-12T23:46 UTC: V_inf 15.167 km/s, CA 3.06 R_S / 123,875 km alt. The Saturn V_inf is higher than Voyager 2's (10.674 km/s) because Voyager 1 took the high-energy Titan-targeted approach. Earth departure (1977-09-05) carries no V_inf entry: no launch C3 / departure V_inf is published in clean form in the acquired literature, and the SPK extractor reads the planetocentric flyby V_inf only. Sourced-only discipline -> the Earth launch is documented (launch_epoch) but not assigned a fabricated departure V_inf. validation_level=V0: the V_inf is DERIVED by our own code (orbit_source = vinf_source = derived), so it classifies 'unvalidated' on the orthogonal provenance-tag tier axis and V0 on the validation_level axis -- the honest floor for a self-derived number, even though the closest-approach geometry it reproduces matches the published mission record to <1%. Admitted as the payoff (parent-reviewed: V_inf validated to <1% against published CA geometry, vis-viva converged). The remaining missions (Galileo, Cassini, Pioneer, Juno) follow the identical SPK-extraction pattern. See docs/notes/2026-06-19-390-spk-vinf-extractor.md and docs/notes/2026-06-19-345-voyager-mariner-mission-digests.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 1 launched 1977-09-05 12:56 UTC (Kohlhase-Penzo 1977 'Voyager Mission Description'; NASA Voyager fact pages).
validity_window.start: Same as launch_epoch (Voyager 1 launch 1977-09-05).
validity_window.end: Saturn closest approach 1980-11-12T23:46 UTC, the last SPK-derived encounter (data/390_mission_vinf.jsonl).
vinf_kms_at_encounters.0.vinf_kms: DERIVED: planetocentric V_inf 10.773 km/s from NAIF SPK vgr1_jup230.bsp (Voyager 1, body -31) at Jupiter closest approach 1979-03-05T12:05 UTC; vis-viva sqrt(v_rel^2 - 2*mu_J/r_rel) converged outside Jupiter SOI (outer-window std 0.006 km/s). CA radius 4.88 R_J independently reproduces the published 4.89 R_J (Kohlhase-Penzo 1977 Table IV JST).
vinf_kms_at_encounters.1.vinf_kms: DERIVED: planetocentric V_inf 15.167 km/s from NAIF SPK vgr1_sat337.bsp (Voyager 1, body -31) at Saturn closest approach 1980-11-12T23:46 UTC (outer-window std 0.030 km/s); CA 3.06 R_S (high-energy Titan-targeted approach).
n_returns: Single Earth launch (1977-09-05) and single Saturn arrival (1980-11-12); n_returns=1 per the v4.7 mga_tour invariant (no continuing tour at Earth).