This is an artist conception of the Total Ozone Mapping Spectrometer, launched onboard an Earth Probe Satellite
(TOMS/EP), in July 1996, is continuing NASA's long term daily mapping of the global distribution of the Earth's atmospheric
ozone. This NASA developed instrument, which measures ozone indirectly by monitoring ultraviolet light, has mapped in detail
the Antarctic "ozone hole," which forms September through November of each year, and the distribution of ozone over the
globe. In addition to ozone, TOMS measures sulfur dioxide released in volcanic eruptions. The U.S. Federal Aviation Administration (FAA) is studying ways to use these measurements to detect volcanic ash clouds that are hazardous to commercial aviation.

Ozone, a molecule made up of three oxygen atoms, shields life on Earth from the harmful effects of the ultraviolet radiation of
the Sun. The increased amounts of ultraviolet radiation that would reach the Earth's surface because of ozone depletion could
increase the incidence of skin cancer and cataracts in humans, harm crops and interfere with marine life. The color on the Earth image depicts ozone values. Normal ozone levels are indicated by the colors green/light blue, low levels
by the colors dark blue/purple and high levels by the orange/yellow colors.

The TOMS instrument is a second generation backscatter ultraviolet ozone sounder. TOMS can measure "total-column-ozone"
the total amount of ozone in a "column" of air from the Earth's surface to the top of the atmosphere under all daytime observing
and geophysical conditions. It consists of an instrument, capable of measuring "total columnar ozone" under all daytime
observing and geophysical conditions. TOMS observations cover the near ultraviolet region of the electromagnetic spectrum,
where sunlight is absorbed only partially by ozone.