Sighting in Ballon Sonde — (reg) Ile-de-France, April 23, 2020

During April 2020, the GEIPAN received five reports from different towns in the Île-de-France region, on different dates. All of them described an unusual luminous phenomenon close to Venus. The sightings took place in the evening, around 8:30 pm for two of them, 8:50 pm for another and 9:10 pm for the last. The investigation report focuses on the 23 April account, which was analysed first: that evening, a witness was smoking a cigarette on their terrace while looking at the sky. They spotted Venus, then a moment later a second point of light almost as bright as Venus.

The investigation found the account to be consistent: there was only one witness, but the description was fairly precise and included a measurement of the phenomenon's position relative to a celestial body. Its residual strangeness was very low. It turned out to be a misidentified weather balloon. A radiosonde launched from the Trappes station was under way at the time of the sighting, and the direction, angular height and bursting time of the balloon matched the observation perfectly.

Météo France confirmed that, during the public-health lockdown in April, the number of weather balloons sent up from Trappes had doubled. This also explains the four other sightings, for which the radiosonde data show excellent agreement, both in the directions of observation and in the times when the phenomenon disappeared. All the reports were grouped into a single case, classified A: weather balloon.