GALILEO 6 (262)

About This Satellite

Galileo 6 shared the August 2014 launch anomaly with Galileo 5, but followed its own recovery campaign. ESA announced its arrival in a corrected target orbit on March 13, 2015. Its recovery followed the earlier work on Galileo 5, illustrating why spacecraft on the same launch can have different commissioning timelines.

A navigation clock became a physics instrument

Galileo 6 and its companion supplied data to the GREAT gravitational-redshift project. Their stable passive hydrogen maser clocks and eccentric orbits allowed researchers to look for a periodic change in clock rate. The useful signal was a carefully measured timing variation, not a visible colour change or a conventional photograph from orbit.

Keep the recovery date separate from the TLE epoch

March 2015 dates a historical recovery milestone. The epoch shown in the orbit panel dates a tracking solution for this particular object. Updating that solution should change the orbital snapshot, but should never move the recovery event into the present or silently declare the navigation service healthy.

Mission reference: ESA: Galileo 6 reaches its corrected orbit. Editorial review: 2026-09-07.

More than a thousand days, not one dramatic pass

ESA's 2018 GREAT report described independent analyses by teams led by ZARM and SYRTE using more than 1,000 days of data. Repeated observations and refinements to orbit modelling helped separate the desired clock behaviour from systematic errors. The conclusions belonged to that measured data set, not to the visual shape of an orbit animation.

Reference: ESA GSSC: GREAT methodology and independent results.

Why laser tracking mattered to a radio-clock experiment

The project used satellite laser ranging to constrain orbit-related uncertainties. If the orbit estimate is imperfect, its errors can contaminate an inferred clock effect. Independent ranging therefore helped assess the measurement rather than replacing the atomic clock. A catalog TLE is suitable for a general trajectory display, but is not the precision orbit solution used in this research.

Reference: ESA Discovery: GREAT results and laser-ranging campaign.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-04. Estimated altitude ranges from 16,880 km at perigee to 26,318 km at apogee, a difference of 9,438 km. The orbital period is about 776.2 minutes. Eccentricity 0.16868 shows why a single altitude cannot describe the whole path. In a two-body approximation, perigee speed is 1.41 times apogee speed. These are mean-element estimates, not instantaneous measurements. Distance per orbit uses an ellipse approximation.

Saved build snapshot. If a valid TLE is retrieved, this explanation and the orbit panel update together. Otherwise this dated snapshot is retained.

Ground track is not sensor coverage

An inclination of 48.81 degrees implies approximate geocentric ground-track limits of 48.8 degrees north and south. This is a prograde orbit, moving in the same general direction as Earth rotation. The plotted line marks the point beneath the object. It does not represent camera coverage, radio reception, or a guaranteed visible pass.

Accuracy and missing information

The introductory record describes the build snapshot. The orbital snapshot explanation and orbit panel share any successfully retrieved TLE; check the displayed epoch. Reentered objects retain historical data only. Mission history is not rewritten by TLE updates. TLE/SGP4 positions are predictions and can change after maneuvers or updated observations. The 14-day stale-data cutoff is a display safeguard, not an accuracy guarantee. Local passes are geometric predictions, not a visibility forecast. No verified operator or mission status means unknown, not active. Do not use this catalog for collision avoidance or operational flight decisions.

Catalog sources: CelesTrak SATCAT: NORAD 40129 · GCAT: S40129 (source update 2026 Sep 4 2345:57). Supplementary metadata: SatNOGS DB, retrieved 2026-09-05T12:57:25.375Z. Page assembled 2026-09-15. GCAT phase codes describe trajectory phases, not mission health.

Learn more: TLE data · Perigee and apogee · Ground tracks · JOT (Jewawud Live Orbital Map)

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