ECHIROLLES (38) 29.07.2024

On 29 July 2024 at about 06:30, two witnesses were outdoors in the commune of Échirolles (38). Looking west, they observed a white point of light moving slowly and steadily on a south-to-north trajectory at a constant elevation of about 60°. No noise was perceived during the observation. After 5 minutes, the phenomenon disappeared to the northwest, masked by the surrounding vegetation. The evidential quality* is considered satisfactory, although only one of the two witnesses completed a questionnaire. A 44-second video of the phenomenon, produced by T1, was obtained and analyzed for the investigation. *According to the GEIPAN criteria, evidential quality is the amount of information collected for an account that is considered reliable and objectively established. Two hypotheses were studied: that of an airplane and that of a balloon, or more precisely, of a cluster of balloons. The aircraft hypothesis initially matched some UAP features—an elongated fuselage-like shape, a common white color and steady straight-line motion—but proved unlikely, mainly due to the absence of such aircraft on radar maps. The balloon cluster hypothesis is more plausible, based on the following elements: - Elongated overall shape and presence of elements in this form resembling individual, round balloons. - White color, common for balloons, and brightness from illumination by the newly risen Sun. - Slow, steady and straight movement, consistent with the behaviour of balloons carried by the wind. - Measurements and calculations from the video fit a windborne balloon cluster 80 cm to 1 m long, about 40–70 m from the witnesses. Wind data showed that it was highly variable, with shearing at all levels between the ground and 500 m altitude, and a wide area in the direction of observation. This variability appears in the output of the fine-resolution AROME* model, which may sometimes differ from those obtained in real time, which is possibly the case here. The orientation of the wind from south to north in the area of displacement of these balloons is therefore possible but not demonstrable. GEIPAN classifies this case as "B": likely observation of a cluster of balloons. AROME (Application of Research to Operations at MEsoscale) is Météo-France’s fine-resolution forecasting model, with a 1.3 km grid.