Total Ozone Mapping Spectrometer/Earth Probe (TOMS) Mission Summary

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.

TOMS/EP measures total ozone by observing both incoming solar energy and backscattered ultraviolet (UV) radiation at six wavelengths. "backscattered" radiation is solar radiation that has penetrated to the Earth's lower atmosphere. There, it is scattered by air molecules and clouds back through the stratosphere to the satellite sensors.

TOMS makes 35 measurements every 8 seconds, each covering 30 to 125 miles (50 to 200 kilometers) wide on the ground, strung along a line perpendicular to the motion of the satellite. Almost 200,000 daily measurements cover every single spot on the Earth except for areas near one of the poles, where the Sun remains close to or below the horizon during the entire 24 hour period.

To ensure that ozone data will be available throughout the next decade, NASA will continue the TOMS program using U.S. and foreign launches. The Japanese Advanced Earth Observations Satellite (ADEOS) will carry a fourth TOMS into orbit when it launches in 1996, and a fifth TOMS Instrument is being assembled for flight in 1998 on an undetermined satellite. The TOMS program is managed by NASA's Goddard Space Flight Center, Greenbelt, Md., for the Office of Mission to Planet Earth, Washington, D.C.

TOMS is part of NASA's Mission to Planet Earth a long term, coordinated research effort to study the Earth as a global environmental system. Using the unique perspective available from space, NASA will observe, monitor and assess large-scale environmental processes, focusing on climate change. MTPE satellite data, complemented by aircraft and ground data, will allow humans to better understand natural environmental changes and to distinguish natural changes from human induced changes. MTPE data, which NASA will distribute to researchers worldwide, is essential to humans making informed decisions about their environment.

September 22, 1997