Ozone (O3) is a constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog. Many highly energetic reactions produce it, ranging from combustion to photocopying. Often laser printers will have a smell of ozone, which in high concentrations is toxic. Ozone is a powerful oxidizing agent readily reacting with other chemical compounds to make many possibly toxic oxides.

The troposphere extends to between 10 and 18 kilometers above the surface of the Earth and consists of many layers. Ozone is more concentrated above the mixing layer, or ground layer. Ground-level ozone, though less concentrated than ozone aloft, is more of a problem because of its health effects.

Tropospheric ozone is a greenhouse gas and initiates the chemical removal of methane and other hydrocarbons from the atmosphere. Thus, its concentration affects how long these compounds remain in the air.

Satellites can measure tropospheric ozone. Measurements specifically of ground-level ozone require in situ monitoring technology.

The Total Ozone Mapping Spectrometer (TOMS) is a satellite instrument for measuring ozone values. Of the five TOMS instruments which were built, four entered successful orbit. Nimbus-7 and Meteor-3 provided global measurements of total column ozone on a daily basis and together provide a complete data set of daily ozone from November 1978 - December 1994. After an eighteen month period when the program had no on-orbit capability, ADEOS TOMS was launched on August 17, 1996 and provided data until the satellite which housed it lost power on June 29, 1997. Earth Probe TOMS was launched on July 2, 1996 to provide supplemental measurements, but was boosted to a higher orbit to replace the failed ADEOS. The only total failure in the series was QuikTOMS, which was launched on September 21, 2001 but did not achieve an orbit. The transmitter for the Earth Probe TOMS failed on December 2, 2006.

Since January 1, 2006 data from the Ozone Monitoring Instrument (OMI) has replaced Earth Probe TOMS.

OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the main scientific imaging system on the orbiter of the ESA spacecraft Rosetta. It was built by a consortium led by the German Max Planck Institute for Solar System Research.

For More Information: Total Ozone Mapping Spectrometer (TOMS)

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