简介

光学设计

大地测量学

天文学

发现小行星

命名事物

简介

尔约·维萨拉（芬兰语：Yrjö Väisälä， [ˈyrjø ˈʋæisælæ]，1891年9月6日－1971年7月21日）是一位芬兰天文学家和物理学家。

维萨拉的主要贡献是光学方面，但他在大地测量学、天文学和光学气象学也有相当贡献。他因此获得绰号“Tuorla（天文台/光学实验室）的魔术师”。另有一本同名的芬兰书籍就是描述他的光学成就。

他的两位兄弟分别是数学家卡利·维萨拉（Kalle Väisälä）和气象学家维尔霍·维萨拉（Vilho Väisälä）。

维萨拉也是相当狂热的世界语支持者。并曾在1968年担任国际世界语科学家协会（世界语：Internacia Scienca Asocio Esperantista）会长。

光学设计

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Contemporary to Bernhard Schmidts design, but unpublished was also Prof.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".

Once he saw Schmidt's publication, he promptly went ahead and "solved" the field flattening problem by placing a doubly convex lens slightly in front of the film holder (back in the 1930s, astronomical films were glass plates.) The resulting system is known as the Schmidt-Väisälä camera or sometimes as the Väisälä camera. (This solution is not perfect, as images of different colour end up at slightly different places.)

Prof. Väisälä made a small test unit of 7 mirrors in a mosaic on stiff background steel frame, however it proved to be impossible to stabilize as "just adjust and forget" structure, and next time anybody tried it, was with active controls on Multiple Mirror Telescope

大地测量学

In the 1920s and 1930s Finlandwas doing its first precision triangulation chain measurements, and to create long-distance vertices Prof. Väisälä proposed usage of flash-lights on 5（altitude balloons, or on some big fireworks rockets. The idea was to measure the exact position of the flash against background stars, and by precisely knowing one camera location, to derive an accurate location for another camera. This required better wide-field cameras than were available, and was discarded.

Later, Prof. Väisälä developed a method to multiply an optical length reference using white light interferometry to precisely determine lengths of baselines used in triangulation chains. Several such baselines were created in Finland for second high-precision triangulation campaign in 1950s and 1960s.

Later GPS made these methods largely obsolete. A Väisälä interferometry baseline is still maintained by the Finnish Geodetic Institute in Nummela for the calibration of other distance measurement instruments.

Prof. Väisälä also developed excellent tools to measure earth rotational axis position by building so called zenith telescopes, and in the 1960s Tuorla Observatory was in the top rank of North Pole position tracking measurements.

In the 1980s radioastronomy was able to replace earth rotation tracking by referring things against "non-moving background" of quasars.

For these Zenith Telescopes, Prof. Väisälä made also one of the first experiments at doing mirrors of liquid mercury. (Such mirror needs extremely smooth rotational speeds which were achieved in the late 1990s.)

天文学

The big Schmidt-Väisälä telescope he built was used at the University of Turku for searching asteroids and comets. His research group discovered 7 comets and 807 asteroids.

For this rather massive photographic survey work, Prof. Väisälä developed also a protocol of taking two exposures on same plate some 2–3 hours apart and offsetting those images slightly. Any dot-pairs that differed from background were moving, and deserved follow-up photos. This method halved the film consumption compared to method of "blink comparing" where plates get single exposures, and are compared by rapidly showing first and second exposures to human operator. (Blink-comparing was used to find e.g. Pluto.)

维萨拉还以发现两颗周期彗星维萨拉彗星（40P/Väisälä）和维萨拉－奥特玛彗星（139P/Väisälä-Oterma）而闻名。后者是和芬兰首位获得天文学博士的女性天文学家利斯·奥特玛（Liisi Oterma）共同发现，起初被赋予小型星临时编号 1939 TN。

发现小行星

维萨拉总共发现了128颗小行星。他使用知道生日的朋友命名这些小行星，其中一位朋友是马蒂·帕洛马（Matti Palomaa）教授的名字被用在小行星1548的命名。因为目前没有小行星以美国加州的帕洛马山天文台（Palomar Observatory），且有一个字母不同，因此符合小行星不得名称重复的规则。

命名事物

月球上的维萨拉环形山

小行星1573和小行星2804

图尔库大学天文系全称“维萨拉太空物理与天文研究所”表示对他的尊敬。