Professor Vilho Väisälä was Vaisala's founder and long-time managing director. Vaisala was his life work.

The first prototype of the radiosonde built by Vilho Väisälä. Taken aloft in December, 1931, this instrument measured temperature only.

The first sounding with a Vaisala radiosonde was performed in Helsinki on December 30, 1931.

Upper air observation equipment at Ilmala Meteorological Station in the 1930's.

The kite was the predecessor of radiosondes. Vilho Väisälä made a number of improvements in the kite method used for studying the atmosphere which made it possible to attain an altitude of up to 5 km, which was quite an achievement at the time.

The first actual delivery of Vaisala radiosondes (product type RS11) to the Massachusetts Institute of Technology took place in 1936. This radiosonde model was complete with pressure, temperature and humidity measurement.