The launch of a new research satellite December 7 is
expected to provide scientists at the National Center for Atmospheric
Research (NCAR) and other institutions with an unprecedented view of
the mysterious upper regions of the earth’s atmosphere. Improved
knowledge of the region —
known as the mesosphere and lower
thermosphere/ionosphere —
could bolster communications networks,
ensure that satellites stay on course, and provide scientists with
greater insight into human influences on the atmosphere. NASA
launched the satellite aboard a Delta II rocket from Vandenberg Air
Force Base in California.

TIMED (which stands for Thermosphere, Ionosphere, Mesosphere,
Energetics and Dynamics) is designed to obtain a global picture of
the portion of the atmosphere from about 40 to110 miles (60-180
kilometers) above the earth’s surface. This complex region, greatly
influenced by the sun, is too high for ground-based instruments to
probe in much detail. The TIMED satellite will provide the first
comprehensive picture of temperature, wind, and chemical composition

“We’re looking at weather at the edge of space,” says NCAR’s Stanley
Solomon, a principal investigator for TIMED. “This interface between
the earth’s atmosphere and space is an extraordinarily variable and
dynamic region.” With TIMED, Solomon believes that scientists will
move to nowcasting the upper atmosphere —
that is, reporting with some
accuracy on current conditions. In a few years, scientists may be
able to provide one-hour forecasts of upper-atmosphere weather.

“This part of the atmosphere is crucial to our understanding of the
overall solar-terrestrial system,” says NCAR director Tim Killeen,
principal investigator for the TIMED Doppler Interferometer (TIDI),
an instrument that will measure globally the speed and direction of
high-atmosphere winds. “TIMED will for the first time thoroughly
probe this region by exploring the full range of atmospheric
parameters, allowing us to establish a pole-to-pole climatology.”

TIDI measurements will provide important information on such upper-
atmosphere phenomena as gravity waves, airglow and auroral emission
rates, noctilucent clouds, and ion drifts, besides basic information
about high-level global winds and temperatures.

The area that TIMED is exploring is profoundly affected by the sun’s
magnetic field and radiant energy. Yet it is the least-understood
region of the atmosphere. Ground-based instruments can detect only a
small portion of it, and sounding rockets provide just a brief
picture of the region before falling back toward the earth.

The TIMED spacecraft is designed for a 388-mile (625-kilometer)
circular orbit around the earth. The spacecraft’s four instruments
will measure solar radiation, auroral energy inputs, temperature,
pressure, key gases, and other characteristics of the upper

The mesosphere and lower thermosphere/ionosphere is attracting the
interest of scientists because of its important impacts on orbiting
vehicles and communications systems. For example, when upper
atmospheric temperatures rise, the resulting expansion pushes
molecules to higher altitudes. This increased density exerts an added
drag on satellites and slows down their orbits. Changes in the
ionosphere can disrupt radio waves and affect the Global Positioning
System (GPS). In addition, bursts of solar radiation can affect
astronauts working on the space station.

“We have a large investment in a space-based economy,” says Solomon.
“This drives our need for a better understanding of issues like the
effects of atmospheric drag on orbits and the effects of the
ionosphere on communications.”

The upper atmosphere may also provide a window into the impacts of
human-generated emissions of methane, carbon dioxide, and other gases
on the lower atmosphere —
some of which have been linked to global

“I’d like to understand the interaction of the energy input of the
sun with the chemical composition and how that interaction controls
the temperature and the wind vectors in the upper atmosphere,” says
NCAR’s Anne Smith, a principal investigator analyzing measurements of
ozone, hydrogen, and other key upper-atmosphere components.

Knowledge of the upper atmosphere lags behind that of the lower
atmosphere by many decades. Scientists lack the data to provide
satellite operators with even the crudest of forecasts about winds,
temperatures, and other conditions in the mesosphere and lower

“Right now, it’s similar to where we were 50 years ago when nobody
believed the weather forecasts,” Solomon explains. “With TIMED, we
will make fundamental advances in understanding this region,” he
predicts. “The next step is to use the basic research to provide real
societal benefits.”

Scientists in NCAR’s High Altitude Observatory and Atmospheric
Chemistry Division are playing key scientific roles. A number of
federal agencies and universities are taking part in the mission.
NCAR’s primary sponsor is the National Science Foundation.

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NCAR’s Stanley Solomon wore a clean-room suit during a firsthand
inspection of the TIMED satellite at Vandenberg Air Force Base in
October. (Photo courtesy S. Solomon, National Center for Atmospheric

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NASA’s TIMED (Thermosphere, Ionosphere, Mesosphere Energetics and
Dynamics) spacecraft–en route to explore one of the last frontiers in
Earth’s atmosphere–successfully launched December 7 at 7:07 a.m. PST,
aboard a Delta II rocket from Vandenberg Air Force Base, California.
(Illustration courtesy NASA.)


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