NASA soon will launch its latest ozone-monitoring instrument, QuikTOMS or Quick Total Ozone Mapping Spectrometer (TOMS), which will allow scientists to continue their long-term measurements of global ozone levels.

An artist's concept of QuikTOMS spacecraft in orbit. Credit: NASA

Built in just two years rather than the traditional three to five, QuikTOMS will take over for the TOMS spacecraft in monitoring global ozone levels (including springtime ozone depletion in both the Arctic and the Antarctic), sulfur dioxide, ash, smoke from fires, and ultraviolet radiation reaching the Earth's surface.

QuikTOMS follows on a 23-year legacy; this type of extended observation allows scientists to distinguish human-forced changes from natural atmospheric variations and helps quantify the roles of these factors. Such extended, calibrated observations are required for researchers to see the future ozone recovery expected as a result of the 1987 Montreal Protocol, as amended, which limited the production of ozone-destroying industrial chemicals such as chlorofluorocarbons (CFCs).

QuikTOMS will allow for continued study of the annually recurring Antarctic ozone hole. The year 2000 marked the largest Antarctic hole ever observed -- 28.3 million square kilometers, roughly three times the size of the United States. QuikTOMS will continue the important job of ozone monitoring now done by the five-year old TOMS instrument on Earth Probe which is beginning to show signs of aging.

"NASA is pleased with Orbital's cooperation, teamwork and dedication throughout the development and launch preparations of the QuikTOMS spacecraft, instrument and launch vehicle," said Kenneth Schwer, the QuikTOMS Project Manager. "NASA's innovative acquisition tools continue to provide excellent avenues for achieving acceptable low-cost and quick missions."

Although the TOMS data will be used primarily to study ozone, the information gained from TOMS will also contribute to volcanic studies. Volcanoes generate sulfur dioxide (SO2) in the Earth's atmosphere, and the TOMS instrument can track this gas. The gas is rapidly transformed into sulfate aerosols, which can persist in the stratosphere for months to years. Sulfur dioxide's effects in the stratosphere include the red sunsets that follow major volcanic eruptions. The effects cause chemical changes in the atmosphere and are associated with climate change.

TOMS also can track smoke from forest fires such as those in the Northwestern United States this year, as well as smoke plumes from fires set to clear land in Africa and South America.

Also aboard Orbital's four-stage ground-launch rocket will be the OrbView-4 high-resolution and hyperspectral imaging satellite that Orbital built for Orbital Imaging Corporation (ORBIMAGE). In addition, the Taurus rocket will carry a small payload for Celestis, Inc., which will not separate from the rocket's final stage once it reaches orbit.

On launch day, the Taurus rocket will be prepared for its mission during a three-hour countdown procedure. Following a final launch decision, the vehicle will ignite its first stage rocket motor, lift off and follow a pre-programmed launch sequence controlled by its onboard flight computer. Approximately 11 and a half minutes after liftoff, Taurus will deliver the OrbView-4 spacecraft into a Sun-synchronous orbit approximately 470 kilometers above the Earth. About two and a half minutes later, Taurus will deploy the QuikTOMS satellite into a Sun-synchronous orbit also 470 kilometers above the Earth. Afterward, the satellite's onboard propulsion system will boost the QuikTOMS spacecraft into its final 800-kilometer orbit.

TOMS is a second-generation, ozone-sounding instrument derived from the Backscatter Ultraviolet (BUV) Spectrometer flown aboard NASA's Nimbus-4 satellite in 1970. The first TOMS instrument was launched aboard Nimbus-7 in 1978. The Nimbus-7 TOMS operated almost continuously from its launch until its failure in 1993, providing more than 15 years of daily global maps of total ozone. The Meteor-3 TOMS, ADEOS TOMS and the Earth Probe TOMS followed the Nimbus-7 TOMS.