Sighting in Cessieu, July 16, 2023

Two witnesses were beside their swimming pool, close to their home, when at 4:30 pm they noticed several objects in a clear, sunny sky moving slowly from the south-east toward the north-west. One of the witnesses described them as a line of four or five clusters, each made up of three luminous spheres of equal size around a larger sphere in the middle. Two other identical clusters moved in the same way, apart from the main formation. Some of the spheres appeared and disappeared one after another, and a few isolated objects seemed to suddenly head back against the general direction of travel. The witness filmed the scene with a smartphone but was disappointed that the video did not show as much detail as the naked eye. It shows light or dark dots moving quickly around the objects.

The investigation concluded that the witnesses had seen a cluster of Mylar novelty balloons carried at altitude by a light wind. The spherical shape, the grouping in threes, the initially straight and steady path, and the brightness, caused by sunlight reflecting off a highly reflective surface, all fit this explanation. AROME data from Météo France confirmed a weak to very weak wind blowing from the south-east to the north-west at roughly 100 to 250 m altitude. The disappearances are explained by the balloons rotating and temporarily presenting a less reflective surface to the sun. The objects moving the opposite way are explained by micro-gusts at altitude, though the resolution of the data made this impossible to demonstrate. The dots in the video are probably video artefacts. It was a summer Sunday, and a party may have taken place in the direction the objects came from, but the investigation could not confirm this. The pilots of gliders flying nearby could not be questioned. GEIPAN classified the case as A.