GALILEO 5 (261)

About This Satellite

Galileo 5 was one of two navigation satellites delivered into incorrect elongated orbits on August 22, 2014, after a Soyuz upper-stage problem. Its story is an example of recovering useful capability from a launch anomaly. The spacecraft was not designed as a dedicated relativity experiment, but its unusual orbit later made that investigation possible.

Recovery changed the orbit without making it nominal

Flight teams raised the low point and reduced the elongation. Galileo 5 reached its corrected orbit in late November 2014, and its navigation and search-and-rescue payloads were switched on for testing the following month. A corrected orbit in this history means a workable recovery target, not the original circular constellation slot.

An eccentric track is not necessarily a plotting error

For this mission, a large difference between perigee and apogee has a documented historical explanation. Compare the dated elements with the recovery history before assuming that the display should resemble a nominal Galileo orbit. The TLE alone cannot determine whether a receiver is permitted to use its navigation message.

Mission reference: ESA: Galileo 5 and 6 launch anomaly and scientific reuse. Editorial review: 2026-09-07.

Why antenna pointing entered the recovery problem

ESA reported that the initial altitude variation confused the Earth sensor used to direct the navigation antennas. The recovery was therefore about more than reaching an attractive orbit on a chart: spacecraft pointing had to remain workable as the satellite moved. Raising perigee helped create conditions for sustained payload testing.

Reference: ESA: recovery geometry and Galileo 5 test campaign.

The unwanted ellipse became a clock laboratory

As Galileo 5 changed altitude, its atomic clock sampled a changing gravitational environment. Researchers used that repeating variation to test gravitational redshift. The scientific measurement required precise clock and orbit analysis; watching the altitude counter here is not a recreation of the experiment. The navigation payload became useful for a question beyond navigation.

Reference: ESA: why the recovered orbit supported a relativity experiment.

Reading this orbital snapshot

Based on TLE epoch: 2026-09-04. Estimated altitude ranges from 16,884 km at perigee to 26,314 km at apogee, a difference of 9,430 km. The orbital period is about 776.2 minutes. Eccentricity 0.16853 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 48.79 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 40128 · GCAT: S40128 (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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