Arthur Covington

Arthur Covington, at Serendipitous Discoveries in Radio Astronomy, Green Bank, WV, May 1983. Arthur Edwin Covington (21 September 1913 – 17 March 2001) was a Canadian physicist who made the first radio astronomy measurements in Canada. Through these he made the valuable discovery that sunspots generate large amounts of microwaves at the 10.7 cm wavelength, offering a simple all-weather method to measure and predict sunspot activity, and their associated effects on communications. The sunspot detection program has run continuously to this day.

Early life and education

Covington was born in Regina and grew up in Vancouver. He showed an early interest in astronomy, and had built a refractor telescope after meeting members of the local chapter of the Royal Astronomical Society of Canada. He was also interested in amateur radio and operated station VE3CC for a time. He started his career as a radio operator on ships operated by the Canadian National Railways. He put himself through school and eventually earned a bachelor's degree from the University of British Columbia in 1938, and obtained his master's degree from the same institution in 1940 after building an electron microscope. He then moved to University of California, Berkeley where he received his doctoral degree in nuclear physics in 1942. He was still at Berkeley when he was invited to join the National Research Council of Canada (NRC) in Ottawa in 1942 as a radar technician, working at the NRC's Radio Field Station.

Solar observations

Immediately after the war Covington became interested in radio astronomy, and built a small telescope out of the electronic parts from a surplus SCR-268 radar combined with parts from another receiver originally built to test silicon crystal radio parts for radar applications. These electronics were attached to the 4 ft (1.2 m) parabolic dish from a Type III gun-laying radar. The system operated at a frequency of 2800 MHz, or a wavelength of 10.7 cm. Initially the instrument was pointed in the direction of various celestial objects, including Jupiter, the Milky Way, aurora borealis, and the Sun, but it proved too insensitive to pick up any source other than the Sun. So a solar study program was started. As time passed, Covington and his colleagues realized that the Sun's emission at 10.7 cm wavelength was varying, which was unexpected. Thinking at that time was that the solar emission at centimeter wavelengths would be simply black body emission from a ball of hot gas.

Covington became convinced that the effect was due to sunspots, as the flux appeared to vary with the number of visible spots. The resolution of the device, about seven degrees, made it impossible to "pick out" a spot on the Sun's surface for study, making a demonstration of the claim difficult. An opportunity to directly measure this possibility presented itself on November 23, 1946, when a partial solar eclipse passed over the Ottawa area, and Covington was able to conclusively demonstrate that the microwave emissions dropped off precipitously when the Moon covered a particularly large sunspot. This also demonstrated that magnetic fields were instrumental in sunspot activity. Here they measured the whole-disk flux and averaged the measurements to produce three highly accurate measurements a day.

He then set about designing an instrument that could directly resolve portions of the sun's disk. The new telescope consisted of a 150 ft (46 m) long section of 3 by 1½ inch metal waveguide cut with slots in locations to create a simple interferometer with a fan-shaped area of sensitivity. The amount of flux gathered was improved by placing the waveguide in metal trough, and the direction of aim could be changed slightly by rotating the waveguide inside the trough, but in general terms it was used to take measurements as the sun passed through its "beam".

Covington's work led to other solar-related discoveries. Observations in 1969 led to the realization that certain types of major sunspot breakouts were preceded by a particular type of radio signal, which allowed advanced prediction of upcoming solar storms. As other teams also started studying the solar flux they noticed that the different teams all came to different conclusions about the total flux, due to differences in the instruments and other effects. Covington worked on an effort to correlate these measurements and solve a single flux number, which was published in 1972. He also played a role in the construction of the Indian River Observatory, an amateur built 200 m interferometer.

Retirement

Covington remained director of the ARO until he retired in 1978. He died in 2001 in Kingston, Ontario, at the age of 88.

Legacy

In 2003, the Dominion Radio Astrophysical Observatory named their new main building in Covington's honour. The Herzberg Astronomy & Astrophysics Research Centre of the National Research Council of Canada established the Covington Fellowship in 2008. Covington had many hobbies including a fondness for rare books, many of which have been donated to Queen's University in the Riche-Covington collection.