Sighting in Vendays-Montalivet, December 12, 2015

Two residents went outside at 6:10 pm to watch an Iridium satellite flare. Four minutes later they noticed a bright, star-like point moving across the sky. It went out and came back on two or three times in a row. The observation lasted about thirty seconds, and only one witness account was collected.

This description is typical of an artificial satellite spinning very fast on itself. Using Calsky to reconstruct satellite passes, the investigation found one object that matched both the time and the trajectory: the SL-23 R/B rocket stage, catalogued as 41107 and 2015-074-C. It was a Zenit rocket stage seen shortly after its launch. Its path, from the southwest toward the east, peaked at about forty degrees above the horizon, which agrees with the height the witness estimated. The object was very easy to see at that moment, and a later visual observation confirmed its variable, spectacular brightness.

GEIPAN classified the case as A: a misidentification of a satellite, namely the SL-23 R/B rocket stage 2015-074-C. It rated the case as moderately strange but sufficiently consistent, and a fairly rare type of misidentification.