I am a new subscriber and I writing because I need your help. I am studying mechanical engineering at the University of Sao Paulo an I also work at USP's Astronomy Divulgation Center. Amateur astronomers and general public as well observed from Sao Carlos, Brazil (22 deg 01' S, 47 deg 54' W, elevation 850 m) the apparition of a strange ball-like white cloud on Friday April 9, 1999 at aproximatelly 23:30 UTC (20:30 local). The small round cloud appeared at about 28 deg Alt, 290 deg Az (in Orion, between the "Orion Belt" and Betelgeuse), grew larger and turned into a smoky ring of a diameter of about 3-5 deg. It lasted about 5 min and appeared to remain fixed related to stars in the background. Other people observed the same phenomenon from nearby cities (including Bauru, 140 km SW) at roughly the same time and in the same part of the sky. We have no explanation so far. Could it had been generated by a Titan 4 rocket (or its payload) launched on that day?. Or by an Ariane 42 (or payload INSAT 2E) launched a few days earlier?. Were phenomena like this one observed before?. Thank you. Aldo Loup.