Photo: contributed
The Dominion Radio Astrophysical Observatory telescope just south of Penticton on White Lake.
Three times a day, a measure is transmitted from the National Research Council’s Domino Radio Astrophysics Observatory to a list of recipients around the world. Some use it directly. Others archive it and make it available on their websites, along with other data.
The measurements are made using two small radio telescopes, called “flow monitors”. The data consists of measurements of the intensity of the emission of solar radio at a wavelength of 10.7 cm. It is used by those who participate in activities where, in one way or another, they are affected by what is making the Sun. These include communications services, space mission managers, and various infrastructure services.
The data is known as “10.7 cm solar radius flux” or simply “F10.7”.
The service has its roots in World War II. In 1942, anti-aircraft radars, which swept across the sky over Britain in search of invaders, suddenly became unusable. Huge signals flooded any possible echo. The display screens, which should have shown radar echoes, were full of random dots and spots. These things are now called “snow.” The radars were blocked.
The first fear was that Britain’s air defenses would be affected by some secret weapon. Then one of the engineers turned off the transmitter of one of the radars and moved the antenna while looking at the screen. Those traffic jams came from the Sun.
It was a relief to know that there were no secret weapons, but because every time the Sun did what it did, the air defenses deteriorated, information about solar “attacks” was kept secret until after the war. .
During this same war, warships at sea used their radar to sweep the horizon for any possible enemy ship. Operators soon realized that when the radar antenna pointed at the rising or setting Sun, any echo in that direction was flooded by the same type of “snow.” Because this phenomenon could be used by potential attackers, it also remained as quiet as possible.
World War II was a high-tech war. He saw an explosion in the use of advanced radar systems and communication devices, along with efforts to fabricate equipment to jam or falsify enemy radar and communication devices. When the war ended there were heaps of advanced electronics that were no longer needed.
The Milky Way’s natural radio broadcasts were discovered in the 1930s, launching the embryonic science of radio astronomy. The availability of military antennas and unwanted reception systems provided a gold mine for making radio telescopes.
During the war, the National Research Council was a hub for the development of radar systems. After the hostilities ended, NRC scientists used fragments of these radar systems to make Canada’s first radio telescope. They aimed the instrument at various objects in the sky, but the only thing they could detect was the Sun. So they decided to accurately measure these solar radio emissions and how they varied.
Early in the war, Britain shared its military secrets with the United States and Canada. They include the resonant cavity magnetron. This device could generate high transmitter power at centimeter wavelengths. It was especially needed for airborne radar systems: short wavelengths make it possible to use smaller antennas.
It is difficult to accommodate large antennas on aircraft. The magnetrons operated at a wavelength of about 10.7 cm, so did the radars and the NRC radio telescope.
It turned out that the measurements of solar radio emissions at this wavelength were a good indicator of the full range of solar activity, so this service has continued to this day.
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• Venus is low in the glow of dawn. To his right are Mars and Jupiter, together, and then Saturn.
• The Moon will reach the first quarter on the 7th, and will be full on the 14th of June.
This article is written by or on behalf of an outsourced columnist and does not necessarily reflect Castanet’s views.