NASA
SATELLITE FLIES HIGH TO MONITOR SUNS INFLUENCE ON OZONE Click
here for more information, images and animations.
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UARS
Spacecraft | | In
October, the Upper Atmosphere Research Satellite (UARS) completed the first measurement
of the solar ultraviolet radiation spectrum over the duration of an 11 year solar
cycle, a period marked by cyclical shifts in the Suns activity.
This long
measurement record by two instruments aboard UARS will give researchers better
insight into how fluctuations in the Suns energy affect ozone and the Earths
climate. In turn, the data set gives scientists tools to document the influence
of man-made chemicals on ozone loss.
Though
mission success was initially declared only 18 months after its launch in September
1991, UARS has continued to track ozone levels and atmospheric gases that react
with ozone. The satellite has now also recorded the Suns influence on ozone
and other gases over an entire solar cycle. During
the 11-year solar cycle the Sun undergoes periodic changes in activity from the
"solar maximum," to a period of quiet called the "solar minimum."
During the solar maximum there are many sunspots, solar flares, and coronal mass
ejections, which can affect communications and the atmosphere here on Earth. Having
a complete solar cycle of data provides information necessary to distinguish the
natural variations in the Earth's atmosphere from man-made variations, said
Charles Jackman, UARS Project Scientist at NASAs Goddard Space Flight Center,
Greenbelt, Md. UARS
has lasted so long that we now have an 11 year mission with a single set of observations
spanning the entire solar cycle, said Gary Rottman, a senior scientist at
the University of Colorado and Principal Investigator for the SOLar Stellar InterComparison
Experiment (SOLSTICE) instrument on UARS. This
complete solar cycle UV radiation dataset provides key measurements toward better
determination of the roles of natural and man-made influences on ozone. Also,
by observing a full solar cycle, scientists hope to use the additional data to
better understand the Suns behavior. Observatories
on the Earth have found fewer sunspots in this solar cycle than the last one,
but UARS measurements indicate the amount of UV radiation that struck Earths
atmosphere during each solar maximum was about the same. The
expected correlation between sunspot activity and UV irradiance over the long
term was not found, said Linton Floyd, a researcher working at the Naval
Research Laboratory, Washington, and Project Scientist for the Solar Ultraviolet
Spectral Irradiance Monitor (SUSIM) instrument on UARS. Floyd hopes that more
long-term records will help clear up such mysteries about the Sun. UARS
includes ten instruments designed to understand the radiation, chemistry, and
dynamics of the Earths upper atmosphere. Of those ten, seven instruments
still work. The
SUSIM and SOLSTICE instruments measure UV light from the Sun and provide insights
into the relationship between UV radiation and atmospheric ozone. These two instruments
were independently calibrated, each providing a check on the other. Another set
of instruments measure gases like ozone, methane, water vapor, and chlorofluorocarbons
(CFCs) in Earths atmosphere. The third group measures winds in the stratosphere,
mesosphere, and the lower thermosphere and help researchers understand the global
movement of gases. In
January 2003, NASA will launch the Solar Radiation and Climate Experiment (SORCE)
satellite, which will provide further measurements of the Sun. By having an overlap
with UARS, NASA will have two satellites making essentially the same measurements
simultaneously, thereby providing a truthing for comparisons and an
even longer term data record, Floyd said.
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UARS
Spacecraft The Upper Atmosphere Research Satellite (UARS) has outlived
its planned lifetime by operating for 11 years with seven of its 10 instruments
continuing to function. UARS' primary mission is to measure ozone and chemical
compounds found in the ozone layer, which affect ozone chemistry and processes.
It also measures winds and temperatures in the upper atmosphere (stratosphere)
as well as energy from the Sun. The
Sun-Earth Connection
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Click
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Two
of UARS' instruments measure small changes in the solar UV spectrum and a third
records the Sun's total energy output. They contributed to discoveries such as
finding a link between the energy given off by the Sun and Earthly wind patterns
that facilitate climate changes. UARS let scientists take into account solar activity
on the ozone layer and the chemistry of the upper atmosphere where it gets absorbed.
Earlier
this year, UARS also allowed scientists to watch the same solar energy take a
toll on the ozone layer by actually working to destroy a portion in the lower
atmosphere and a small amount of the crucial upper atmospheric ozone layer. The
energetic particles hitting the camera on the second image break down ozone molecules
in much the same way as CFCs. These images of the Sun were taken with the Solar
and Heliospheric Observatory (SOHO). Solar
Cycle During
the Sun's eleven-year cycle, it goes from a minimum (seen here in 1996) to a maximum
(2000) period of activity that affects us everyday. When particularly active,
solar storms can spew tons of radiation to Earth in the form of Coronal Mass Ejections
(CMEs) that can affect power grids, spacecraft, and communication systems. Credit:
NASA
/ ESA Ozone
Contributions
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4 | Click
on image to view animation. The image shows the Antarctic ozone hole maximum for
2002. | Pictured
in the animation are the largest Antarctic 'hole' (2000) and the region of low
ozone over the Arctic, which reached its high in 1999. In 2000 UARS scientists
found that the Arctic ozone may not be recovering as quickly as previously thought.
They attributed this to more than expected polar stratospheric clouds forming
high above the Arctic. They provide the vehicles which convert benign forms of
chlorine into reactive, ozone-destroying forms but they also remove nitrogen compounds
that act to moderate the destructive impact of chlorine. UARS
also facilitated the first study to link greenhouse gases to increased ozone depletion
over populated areas in 2001. Scientists detected increasing water vapor in the
stratosphere resulting partially from greenhouse gases that may delay ozone recovery
and increase the rate of climate change. The study worked because scientists were
able to best simulate the behavior of temperature and ozone in the upper atmosphere
when adding water vapor data from UARS into the climate model. Back
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