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article imageQuicktoms Ozone Monitoring Instrument Prepared For Launch

By Cynthia M. O     Sep 18, 2001 in Technology
WASHINGTON - NASA soon will launch its latest ozone-monitoring
instrument, which will allow scientists to continue their
long-term measurements of global ozone levels. The QUIKTOMS
or Quick Total Ozone Mapping Spectrometer (TOMS) is scheduled
to lift off from Vandenberg Air Force Base, Calif., at 2:49
p.m. EDT on September 21, on an Orbital Sciences Corporation
Taurus rocket.
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.
More information on QuikTOMS, TOMS and OrbView-4 is available
on the Internet at:
http://www.gsfc.nasa.gov/topstory/20010705quiktoms.html
http://toms.gsfc.nasa.gov
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