Stratoscope
Stratoscope (from Latin stratum , ceiling and Greek skopein , to look at) is an astronomical telescope that is carried up into the stratosphere by one or more balloons . This can significantly reduce the adverse effects of the earth's atmosphere (such as the absorption of UV light or X-ray radiation) when observing astronomical objects. The process was first used in France in 1875 . In the 20th century , this method made it possible for the first time to obtain information about water vapor in the atmospheres of Mars and Venus , as well as important knowledge about the sun. Stratoscopes on unmanned balloons can now reach heights of over 40 km. They therefore still represent a sensible and, above all, inexpensive alternative to space telescopes .