Weather balloon
A weather balloon was a device used on 20th century Earth by the United States Army Air Forces and other agencies to assess wind speed and other meteorological conditions. 

During this period, many UFO sightings were officially dismissed by government agencies as weather balloons. In 1947, after recovering and subsequently losing the time-displaced Ferengi shuttle Quark's Treasure, the United States Army Air Forces released a statement that, as opposed to having recovered an extraterrestrial spacecraft, they had only found a weather balloon. (, ) In 1996, while entering a low orbit to make use of their emergency transporters, the similarly time-displaced USS Voyager was captured on videotape and was ruled out as being a weather balloon by a local news report. ()

On the planet Malcor III, the hospital administrator Berel told Riker (surgically altered to appear Malcorian) that the new era of Malcorian space flight had inflamed the imaginations of the Malcorians, causing many of them to see unidentified vessels in the sky which later turned out to be "weather balloons". ()

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Meteorology
Probes