Canadian Geographic
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The North from Space

Ozone


The ozone layer in the Earth’s atmosphere protects our planet from UVB radiation from the sun, which can be harmful to life. Human-made chemicals such as chlorofluorocarbons (CFCs) react with sunlight and destroy ozone.

The Far North is especially vulnerable to the effects of ozone depletion. People exposed to more UVB rays are at higher risk of developing skin cancer, eye damage and weakened immune systems. By tracking the ozone layer’s depletion, we may be able to identify how it can be restored and preserved.

Despite measures taken to protect the ozone layer, it is becoming severely depleted in the Arctic during late winter and early spring. In winter, when much of the region north of the Arctic Circle sees little or no sunlight, unstable conditions in the atmosphere cause chemical reactions unique to the polar regions. When daylight returns in the spring, ultraviolet light from the sun causes the release of ozone-depleting molecules. When the seasons change again, the ozone-depleting molecules become trapped.

Some satellites are dedicated to monitoring the chemical composition of the ozone layer, particularly above the Arctic, where the chemistry is very different from the ozone above Antarctica. There are variations in the extent of the hole in the ozone layer from year to year, and it is not always clear whether they are natural or due to human impact.

SCISAT-1, a satellite launched by NASA in 2003 and the first Canadian scientific satellite to be launched since 1971, includes two instruments that document the chemical processes involved in the depletion of the ozone layer: the ACE (Atmospheric Chemistry Experiment), currently conducted through York University, and MAESTRO (Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation). Using data from this satellite, scientists can measure changes in the size of the ozone layer, particularly over Canada and the Arctic.

To identify and measure the concentration of the 30 to 35 types molecules that make up the Earth’s atmosphere, including ozone, SCISAT uses sunlight. The concentration of each molecule is measured based on the amount of sunlight it absorbs.

In addition to the satellites, Canada also has a network of land-based, ozone-monitoring stations, each housing a spectrophotometer developed by Environment Canada. These have been measuring the ozone layer over Canada for more than three decades. Satellite data, however, have the added advantage of reaching the Far North.

OSIRIS, a Canadian Space Agency (CSA) instrument on board the Swedish Odin satellite, is another mission dedicated to monitoring particles in the ozone layer. When it became operational in 1992, Odin was meant to function for two years, but it has now been gathering data for more than a decade. During the planning stages of this mission, the CSA collaborated with Sweden to develop an instrument that could examine light from the sky to measure ozone in the stratosphere, the middle layer of the atmosphere, which ranges from 20 to 50 kilometres above the Earth’s surface.



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Satellites


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Quiz :

In 2018, which mission is planned to launch?

The Polar Communication and Weather mission
The OSIRIS mission
Pan American Mission