Louis Oscar Sordahl, American astrophysicist, was the son of Olaf Olson Sordahl and Lizabeth Gunnarsdtr Helgoysjoen. He graduated at the University of Wisconsin and in 1928 was co-author, with L.R. Ingersoll, of a paper on "Effect of high cathode temperatures on the rate of sputtering of metals" (Physical Review, 1928). During that year, and up to June1929, he served as assistant at the solar radiation station on Table Mountain, California, erected by the Astrophysical Observatory (Directed by Dr C.G. Abbot*) of the Smithsonian Institution. In August 1929 Abbot appointed him as field director of the solar radiation station on Mount Brukkaros, South West Africa (now Namibia), where he succeeded William H. Hoover*. He arrived at Brukkaros on 3 September 1929, two days before Hoover's departure, and was accompanied by his wife, Mrs Margaret Sordahl* (born Froiland. married in 1928) and by an assistant, Alfred G. Froiland (a younger brother of his wife).
Observations were continued at the site as during the previous three years [see Hoover, W.H.] until November 1931 with only minor interruptions. The most noteworthy of these occurred on the night of 23 January 1930 when the station was struck by lightning. The bolometer, a resistance box and some wiring were burnt out. Fortunately a spare bolometer was available and Sordahl was able to repair the damage with the loss of only four observing days. Results were regularly sent to Dr Abbot in the United States, who compared them to those of the Astrophysical Observatory's other solar stations and interpreted and published the results [see Abbot, C.G.]. Sordahl's skills with tools and materials was also shown at Brukkaros by the construction of a solar water heater, which proved to be quite effective. However, despite his repeated efforts to convince local people of its utility and economic benefits they remained unconvinced.
Sordahl's assistant, Froiland, was recalled to Washington before the end of his term, departing on 20 March 1931, but he was still employed in the Astrophysical Observatory in 1952. His duties at Brukkaros were taken over temporarily by local appointees Arthur E. H. Bleksley (for six months) and D.J. Hatting (for four weeks) after which Mrs Sordahl took over some of the work. The observations at Brukkaros were discontinued on 20 November and the station closed in December 1931. Sordahl and his wife left Keetmanshoop on Christmas day to return to the United States. He had been considering other employment while at Brukkaros and left the Astrophysical Observatory on 30 June 1932. For the next few years he was associated with the Physical Laboratory of the University of Wisconsin and was co-author of two articles on the emission of thermionic electricity from the element columbium [now known as niobium] in the journal Physical Review (1933, 1934, with H.B. Wahlin).
