Yrjö Väisälä [ˈyrjø ˈʋæisælæ] (6 September 1891 – 21 July 1971) was a Finnish astronomer and physicist.

His main contributions were in the field of optics, but he was also very active in geodetics, astronomy and optical metrology. He had even an affectionate nickname of Wizard of Tuorla (Observatory/Optics laboratory), and there is a book with the same title in Finnish describing his works.

His brothers were mathematician Kalle Väisälä and meteorologist Vilho Väisälä.

Väisälä was also a fervent supporter of Esperanto, presiding the Internacia Scienca Asocio Esperantista ("International Association of Esperanto Scientists") in 1968.

Optician

He developed several methods for measuring the quality of optical elements, as well as a lot of practical methods of manufacturing said elements. This allowed the construction of some of the earliest high-quality Schmidt cameras, in particular a "field-flattened" version known as Schmidt-Väisälä camera. Contemporary to Bernhard Schmidt's design, but unpublished was also Prof. Yrjö Väisälä's identical design which he had mentioned in lecture notes in 1924 with a footnote: "problematic spherical focal surface".

Vaisala (Finnish pronunciation: [ˈʋæi̯sælæ]) is a Finnish company that develops, manufactures and markets products and services for environmental and industrial measurement.

The 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 1,600 employees and net sales of €299.7 million in 2014. Vaisala serves customers in more than 140 countries; operations outside Finland accounted for 97% of net sales in 2014.

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, the United Kingdom, Canada, France, Germany, China, India, Sweden, Malaysia, South Korea, Brazil, United Arab Emirates, Japan and Australia.

History

Vaisala's origins date back to 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.

Vaisala can refer to;

Vaisala is a small village on the northwest coast of Savai'i island in Samoa. The village lies within the political district of Vaisigano.

It is located close to the coast in the northwestern corner of the island. To the west are the neighbouring villages of Auala and Asau.

A significant family from Vaisala is the Va'ai family. Va'ai Kolone, a matai, was a Member of Parliament of the Vaisala area who became a Prime Minister of Samoa twice in the 1980s. A progressive leader, he was also the founder the Human Rights Protection Party which has since been the dominant party in Samoan politics and currently in power. Va'ai Kolone's father, a government clerk in the German administration of Samoa during colonialism, foresaw the importance of education and sent his own sons to boarding schools in the capital Apia.

The Vaisala Hotel situated at a white sandy beach is one of the largest hotels at the west end of Savai'i.

In 2009, the village council of chiefs banished their Member of Parliament for the Vaisigano No. 1 district, Va’ai Solia Papu Va’ai, over a domestic dispute. He was allowed to return a few months later following a presentation of gifts and reconciliation with the chiefs. In 2007, the same Member of Parliament had survived being shot by a gunman while attending a meeting in the village of Falealupo.