Arthur Covington
Encyclopedia
Arthur Edwin Covington is a Canadian physicist
who made the first radio astronomy
measurements in Canada. Through these he made the valuable discovery that sunspot
s 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.
and grew up in Vancouver
. He showed an early interest in astronomy
, and had built a 5 inches (127 mm) 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 Railway
s. He put himself though 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 in 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 (NRC) in Ottawa
in 1942 as a radar technician, working at the NRC's Radio Field Station.
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.
It was entirely by accident that the original instrument operated on frequencies suitable to detection of the 10.7 cm signal, and it had never been intended for "production" use. As the importance of the sunspot measurements became obvious, plans were made to continue these observations over a longer time period. As the Radio Field Station was still actively being used for radar development, and causing heavy interference as a result, a new location was selected about five miles (8 km) away at Goth Hill. 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". The new telescope started operation in 1951, allowing them to directly measure the flux from the Sun’s corona and the temperature of the regions above sunspots (about 1,500,000 °C). The Goth Hill observatory also included a number of other instruments for a variety of measurements.
(ARO) in Algonquin Park, about 150 km northwest of Ottawa but relatively easy to access on major highways. A new 6 ft (1.8 m) parabolic dish solar flux telescope was built in 1960, operating in parallel before taking over duties from the Goth Hill instrument in 1962. In 1964 an identical instrument was installed at the Dominion Radio Astrophysical Observatory
(DRAO) in British Columbia
. This was followed by a more powerful version of the waveguide instrument, this time focused by a series of thirty-two 10 ft (3 m) dishes arranged over a 700 ft (215 m) waveguide, which opened in 1966.
The ARO was greatly expanded in 1966 with the opening of the 150 ft (46 m) deep-space telescope. This was a major research site through the 1960s and 70s, although limitations in its design made it see less use in the 1980s. For some time this instrument was joined by a smaller 18 m telescope originally located at the David Dunlap Observatory
outside Toronto
, operated by the University of Toronto
. The original solar observatories remained in use until 1990 when funding drawdowns at the NRC forced the closure of the entire Algonquin site. In 1991 the 1.8 m dish was moved to the DRAO as a backup instrument.
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.
in the Riche-Covington collection.
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
who made the first radio astronomy
Radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
measurements in Canada. Through these he made the valuable discovery that sunspot
Sunspot
Sunspots are temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, which inhibits convection by an effect comparable to the eddy current brake, forming areas of reduced surface temperature....
s 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 ReginaRegina, Saskatchewan
Regina is the capital city of the Canadian province of Saskatchewan. The city is the second-largest in the province and a cultural and commercial centre for southern Saskatchewan. It is governed by Regina City Council. Regina is the cathedral city of the Roman Catholic and Romanian Orthodox...
and grew up in Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...
. He showed an early interest in astronomy
Astronomy
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...
, and had built a 5 inches (127 mm) refractor telescope after meeting members of the local chapter of the Royal Astronomical Society of Canada
Royal Astronomical Society of Canada
The Royal Astronomical Society of Canada is a national, non-profit, charitable organization devoted to the advancement of astronomy and related sciences. At present, there are 29 local branches of the Society, called centres, located in towns and cities across the country from St. John's,...
. He was also interested in amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
and operated station VE3CC for a time. He started his career as a radio operator on ships operated by the Canadian National Railway
Canadian National Railway
The Canadian National Railway Company is a Canadian Class I railway headquartered in Montreal, Quebec. CN's slogan is "North America's Railroad"....
s. He put himself though school and eventually earned a bachelor's degree
Bachelor's degree
A bachelor's degree is usually an academic degree awarded for an undergraduate course or major that generally lasts for three or four years, but can range anywhere from two to six years depending on the region of the world...
from the University of British Columbia
University of British Columbia
The University of British Columbia is a public research university. UBC’s two main campuses are situated in Vancouver and in Kelowna in the Okanagan Valley...
in 1938, and obtained his master's degree from the same institution in 1940 after building an electron microscope
Electron microscope
An electron microscope is a type of microscope that uses a beam of electrons to illuminate the specimen and produce a magnified image. Electron microscopes have a greater resolving power than a light-powered optical microscope, because electrons have wavelengths about 100,000 times shorter than...
. He then moved to University of California in 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 (NRC) in Ottawa
Ottawa
Ottawa is the capital of Canada, the second largest city in the Province of Ontario, and the fourth largest city in the country. The city is located on the south bank of the Ottawa River in the eastern portion of Southern Ontario...
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 radarSCR-268 radar
The SCR-268 was the US Army's first radar system. It was developed to provide accurate aiming information and used in gun laying systems and directing searchlights against aircraft....
combined with parts from another receiver originally built to test silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
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
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
, the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
, aurora borealis, and the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
, 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
Black body
A black body is an idealized physical body that absorbs all incident electromagnetic radiation. Because of this perfect absorptivity at all wavelengths, a black body is also the best possible emitter of thermal radiation, which it radiates incandescently in a characteristic, continuous spectrum...
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
Solar eclipse
As seen from the Earth, a solar eclipse occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially blocks the Sun as viewed from a location on Earth. This can happen only during a new moon, when the Sun and the Moon are in conjunction as seen from Earth. At least...
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.
It was entirely by accident that the original instrument operated on frequencies suitable to detection of the 10.7 cm signal, and it had never been intended for "production" use. As the importance of the sunspot measurements became obvious, plans were made to continue these observations over a longer time period. As the Radio Field Station was still actively being used for radar development, and causing heavy interference as a result, a new location was selected about five miles (8 km) away at Goth Hill. 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
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
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". The new telescope started operation in 1951, allowing them to directly measure the flux from the Sun’s corona and the temperature of the regions above sunspots (about 1,500,000 °C). The Goth Hill observatory also included a number of other instruments for a variety of measurements.
ARO
Increasing radar and radio use in the Ottawa area presented interference problems, and Covington turned his attention to finding a more suitable "radio quiet" location for the program. This led to the creation of the Algonquin Radio ObservatoryAlgonquin Radio Observatory
The Algonquin Radio Observatory is a radio telescope research facility located in the Algonquin Provincial Park in Ontario, Canada. The site's primary instrument is a major 46 m parabolic-dish radio antenna. This instrument is historically famous for taking part in the first successful very...
(ARO) in Algonquin Park, about 150 km northwest of Ottawa but relatively easy to access on major highways. A new 6 ft (1.8 m) parabolic dish solar flux telescope was built in 1960, operating in parallel before taking over duties from the Goth Hill instrument in 1962. In 1964 an identical instrument was installed at the Dominion Radio Astrophysical Observatory
Dominion Radio Astrophysical Observatory
The Dominion Radio Astrophysical Observatory is a research facility founded in 1960 and located south-west of Okanagan Falls, British Columbia, Canada. The site houses three instruments – an interferometric radio telescope, a 26-m single-dish antenna, and a solar flux monitor – and...
(DRAO) in British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
. This was followed by a more powerful version of the waveguide instrument, this time focused by a series of thirty-two 10 ft (3 m) dishes arranged over a 700 ft (215 m) waveguide, which opened in 1966.
The ARO was greatly expanded in 1966 with the opening of the 150 ft (46 m) deep-space telescope. This was a major research site through the 1960s and 70s, although limitations in its design made it see less use in the 1980s. For some time this instrument was joined by a smaller 18 m telescope originally located at the David Dunlap Observatory
David Dunlap Observatory
The David Dunlap Observatory is a large astronomical observatory site once owned by the University of Toronto, located just north of the city in Richmond Hill, Ontario within a estate. Its primary instrument is a 74-inch reflector telescope, at one time the second largest telescope in the world,...
outside Toronto
Toronto
Toronto is the provincial capital of Ontario and the largest city in Canada. It is located in Southern Ontario on the northwestern shore of Lake Ontario. A relatively modern city, Toronto's history dates back to the late-18th century, when its land was first purchased by the British monarchy from...
, operated by the University of Toronto
University of Toronto
The University of Toronto is a public research university in Toronto, Ontario, Canada, situated on the grounds that surround Queen's Park. It was founded by royal charter in 1827 as King's College, the first institution of higher learning in Upper Canada...
. The original solar observatories remained in use until 1990 when funding drawdowns at the NRC forced the closure of the entire Algonquin site. In 1991 the 1.8 m dish was moved to the DRAO as a backup instrument.
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
Arthur remained the director of the ARO until he retired in 1978. He died in 2001 in Kingston, Ontario, at the age of 88.One of the buildings at the Dominion Radio Astrophysical Observatory was named in his honour in 2003. He had many hobbies including a fondness for rare books, many of which have been donated to Queen's UniversityQueen's University
Queen's University, , is a public research university located in Kingston, Ontario, Canada. Founded on 16 October 1841, the university pre-dates the founding of Canada by 26 years. Queen's holds more more than of land throughout Ontario as well as Herstmonceux Castle in East Sussex, England...
in the Riche-Covington collection.