Noun
English Wikipedia has an article on:observation balloonWikipedia
observation balloon (plural observation balloons)
(military) A type of balloon that is employed as an aerial platform for intelligence gathering and artillery spotting.
Synonym: scout balloon
Several Confederate soldiers saw the Union observation balloon Eagle soaring overhead and assumed that they could likewise be seen, but no such report was sent to headquarters. Source: Internet
This type of parachute was first adopted on a large scale for their observation balloon crews by the Germans, and then later by the British and French. Source: Internet