Vaisala Oyj () is a Finnish company that develops, manufactures and markets products and services for environmental and industrial measurement. Their major customer groups and markets are national meteorological and hydrological services, aviation authorities, defense forces, road authorities, the weather critical energy sector, life science and high-technology industries and building automation. Vaisala had over 1,900 employees and net sales of €379.5 million in 2020. Vaisala serves customers in more than 150 countries. The parent company Vaisala Oyj, domicile in Vantaa, Finland, is listed on the NASDAQ OMX Helsinki. Vaisala Group has offices and operations in Finland, the United States, Australia, Brazil, Canada, China, France, Germany, India, Italy, Japan, Kenya, Malaysia, México, South Korea, Sweden, United Arab Emirates, and the United Kingdom. History Vaisala originated in the 1930s when Professor Vilho Väisälä (1889–1969), Vaisala's founder and long-time managing director, invented some of the operating principles of a radiosonde. He sent the first Finnish radiosonde aloft in December 1931. After the first sounding, Väisälä continued with further development and tests until a radiosonde could be brought into production and deliveries started in 1936. From the very start, Vaisala was an international business, exporting 95 percent of the production. As the Vaisala radiosonde became internationally renowned, the demand for them increased. In 1944, Prof. Väisälä established a company called Mittari Oy ("Gauge Incorporated") and set up manufacturing facilities for radiosonde systems. The first sounding system included a semi-automatic radiosonde receiver, a calibration device and a ground check set. The company employed 13 people at the time. Later, in 1955, the name of Mittari was changed to Vaisala. From a modest start, the company evolved to become a world leader in many measurement fields and to establish a noteworthy Finnish export industry. At the end of 1954 a modern manufacturing plant was relocated in Vantaa. Since then, the headquarters have been expanded several times and Vaisala's product range has been diversified and expanded greatly. Nowadays Vaisala employs over 1,800 people and serves customers in over 150 countries. Commercial production since 1936 After the first sounding, Väisälä continued with further development and tests until a radiosonde could be brought into commercial production. Radiosonde deliveries started with the RS11 (1936–). Amongst its first customers was the Massachusetts Institute of Technology. In 1937, Väisälä's radiosonde won a gold medal at the World Fair in Paris. Recovering from the wars World War II, the Finnish Winter War 1939–1940