Ilha da Trindade, Brazil: Balloon is drawn into a cloud, silvery half-moon object emerges
On the morning of 6 January 1958 Capt. Carlos Alberto Bacellar, tracking a weather balloon at the meteorological station on Ilha da Trindade, Brazil, saw the balloon drawn into a cloud and lose its instruments; a silvery object resembling a bright white half-moon then emerged and he followed it by theodolite for 30 minutes.
Background
Capt. Carlos Alberto Bacellar was tracking a weather balloon launch at the meteorological station on Ilha da Trindade when the balloon's radio signals faded without a loss in frequency and its transmitter fell silent. The balloon was still visible approaching a cumulus cloud at 14,000 feet; it was suddenly sucked up into the cloud and reappeared 10 minutes later, ascending more rapidly, as if it had released its instrument pack inside the cloud. No parachute was seen and the instruments were never recovered. A silvery object emerged from the cloud; through the 20x theodolite it looked like a bright white half-moon, and Bacellar followed it for 30 minutes until it disappeared in a cloud bank. Eberhart cites Olavo T. Fontes in the APRO Bulletin (January 1960) and Clark's encyclopedia. The account follows the entry in George M. Eberhart's chronology UFOs and Intelligence (CUFOS) and the sources cited there; it is not an independent determination by From Beyond Space.