Sighting in Saint-Denis, June 9, 2017

In the early afternoon, a witness noticed a white dot that seemed motionless against a blue sky. It eventually began to move. The witness took out their smartphone and filmed it as it passed in front of a cloud. They lost sight of it behind the cloud, then saw it come out again and resumed filming. GEIPAN received both original videos, but only one account was collected.

The investigation showed that the witness had almost certainly seen the weather balloon launched every day at 15:00 local time from the Gillot station for radiosonde soundings. Several points support this conclusion: the dot's round shape and white colour matched those of a weather balloon; a balloon launch had indeed taken place about a quarter of an hour before the sighting; the witness was about 4 km from the launch site; and the dot's movements were consistent with a balloon gaining altitude and little affected by the weak winds at the heights where it was observed and filmed. The phenomenon had all the physical and dynamic characteristics expected for this explanation. The case was classified A: confusion with a weather balloon.