EVRY-COURCOURONNES (91) 28.06.2023

On 28 June 2023, around 7 pm, at EVRY-COURCOURONNES, the witness, inside the stadium in Parc des Loges, (91) observed a UAP moving in the sky. He immediately recorded a 4 minute video. The description of the appearance and behaviour of the UAP, as visible on this video and corroborated by the testimony, is as follows: - round and black object, without additional features such as halo or specific structure. The witness notes a metallic appearance, not visible on the video. - the object appears to be at low altitude (at one of the stadium's streetlights), moving slowly and noiselessly. It disappears after a few minutes, moving away while ascending into the sky. According to the witness, its trajectory is described as "straight and ascending, with apparently random movements at high altitude". Only one testimony is collected. The visual cues on the video and the schematic indications provided by the witness enabled GEIPAN to reconstruct the orientation of the UAP movement, which is heading from east to west. However, there is still a margin of uncertainty due to the difficulties in positioning the UAP accurately, particularly at the beginning of the observation. According to the GEIPAN criteria, the evidential quality* of this case is considered good, despite the initial absence of azimuth data, which GEIPAN was able to reconstruct, and the fact that there is only one witness, since the latter nevertheless provided a usable video of the UAP (* evidential quality is the amount of information considered reliable, collected for testimony). The hypothesis explored is that of a simple helium-filled balloon and for which the following elements agree: - round shape, quite consistent with that of such a balloon, - The black color is plausible. The metallic appearance reported by the witness suggests that the balloon could be made up of an aluminized envelope (Mylar type), a material commonly used for helium-inflated balloons. - slow, straight and ascending movement, which is perfectly compatible with the normal behaviour of such a balloon. The more erratic movements observed by the witness at a higher altitude are compatible with the presence of more irregular winds, including wind shear, at these altitudes. However, these phenomena cannot be formally demonstrated with the meteorological data available, as they can occur on a very small scale. As for the direction of displacement, weather data indicate that the wind was blowing weakly, which is consistent with the slow displacement of the UAP. The wind orientation was rather northeasterly, which is consistent with the observed direction of the UAP, despite the various uncertainties. (See weather document for UT time, with a two-hour lag from the time of observation; the DD symbols indicate wind direction and FF wind force). The witness considered the possibility of a balloon from the outset, but dismissed it for the following reasons: - "The sphere seems quite solid when it moves": this impression is probably due to the black color, the metallic appearance and the perfectly round shape of the ball, which can actually give the illusion of a solid object, made of solid metal. - "The object is perceived to move differently by changing direction": as already explained, this change of direction, which was not constant throughout the observation but only when the UAP reached a certain altitude, is due to changing and more irregular winds encountered at this altitude. - "It does not fit a common helium balloon, knowing that no string was present." A string is not always present, or it may have been detached from the balloon or cut. As for the spherical shape, it is quite common for a Mylar balloon inflated with helium, usually available for sale on the Internet. The origin of this balloon could not be determined during the investigation. However, it should be noted that the area is surrounded, to the north and east, by many educational establishments (primary schools, middle schools and high schools), so it is possible that a balloon was released or lost during celebrations at the end of the school year. The GEIPAN classifies the case as A, observation of an ordinary balloon.