[MIham] Aura to examine atmosphere

[FSK]

  *Earth's Air: NASA's Aura Spacecraft to Gauge Atmospheric Health*

By Tariq Malik
Staff Writer
posted: 07:00 am ET
09 June 2004

Humans can live without a lot of things on Earth, cable television and
Twinkies for example, but air isn't one of them.

Now a new NASA satellite is poised to take the closest look ever at the
air humans breathe to understand how smoke, aerosols and other
pollutants can be carried through the atmosphere and affect air quality
around the world.


The Aura spacecraft, the latest and last satellite NASA's first Earth
Observing System (EOS), will also monitor changes in Earth climate and
search the planet's ozone layer for any signs of recuperation after
years of attack by man-made pollutants like chlorofluorocarbons (CFCs).

"It truly is a chemistry lab in space," said Michael Tanner, Aura's lead
engineer and the mission's program executive at NASA headquarters, of
the spacecraft. "If it works for one day we will have more information
on our air than ever seen from space."

Aimed for an orbital slot some 438 miles (705 kilometers) above Earth,
Aura will focus its attention on the stratosphere, home to the ozone
layer, and the layer of breathable air stretching down to ground level.
The spacecraft will fill the atmospheric gap left by its EOS satellite
comrades Aqua, which studies Earth oceans, and Terra, aimed at landmasses.

The spacecraft is expected to launch no earlier than July 3, 2004.

The air we breathe

Nestled among the four instruments aboard Aura is a device called the
Tropospheric Emission Spectrometer (TES) that will study a layer of the
atmosphere in which most people live, work and play.

That layer, the troposphere, starts on the ground and stretches about
six miles (10 kilometers) up to the stratosphere, where the ozone layer
screens the planet from ultraviolet radiation.

Space-based observations of the troposphere are traditionally difficult
due to interference from clouds that sit between satellites and the
atmosphere's bottom-most layer. Aura's TES instrument, however, is
designed look downward and horizontally at the same time. The
configuration should be able to track air pollution caused by Mother
Nature from volcanoes or wildfires, as well as by man, including the
burning of trees and other biomass in the tropics and industrial
byproducts in North America and China.

"Mostly, it's considered a local problem, but it's really a global one,"
said Aura project scientist Mark Schoeberl, based at NASA's Goddard
Space Flight Center, during a telephone interview. "We need to
understand how well pollutants can get from the United States to Europe,
for example."

Dust from deserts in China, for example, can waft out over the Pacific
Ocean and affect air quality in the Pacific Northwest, and smoky air
from Canadian wildfires stretched from New York to Washington D.C. in
2002.

But with a better understanding of how such pollutants are transported
through the atmosphere, researchers would be better equipped to issue
air quality warnings for residents who might otherwise suffer health
problems.

Ozone check-up

Aura's second target is the ozone layer in the stratosphere, a
protective layer of the atmosphere that has been closely-watched since
the 1970s when satellite measurements first began recording signs of
ozone depletion due to man-made CFC pollution.

The spacecraft's Ozone Monitoring Instrument (OMI) will map changes in
the ozone layer as well as the levels of nitrogen dioxide and other
pollutants. Along with two other Aura instruments, OMI should help
researchers pin down any mixing between protective ozone in the
stratosphere and pollution-generated ozone in the upper troposphere.

"There is such a thing as good ozone and bad ozone," Tanner told
SPACE.com.

Aura instruments are also designed to detect greenhouse gas levels and
measure how aerosol particles reflect or absorb sunlight, which could
contribute to climatic changes such as global warming and cooling trends.

An atmospheric "A" train

The Aura spacecraft won't be alone in space during its planned six-year
mission.

Once aloft, Aura will trail the Aqua spacecraft in a formation flight
pattern to make comprehensive climate observations of the Earth. In
2005, the cloud-watching satellites - CloudSat and the CALYSPO - are
expected to fill in the gap between the two EOS spacecraft, with the
French-developed PARASOL satellite to join them in 2006.

Mission scientists have dubbed the five-spacecraft formation the
"A-train," in which each spacecraft passes over a region 15 minutes
after its predecessor and takes data that can ultimately be combined
into a complete climate picture.

"We've come up with this sort of super assault on the atmosphere," said
Schoeberl, adding that while the multiple spacecraft will follow each
other, they will be at different orbital inclinations. "We'll really be
able to look at the interaction between the climate and the atmosphere."

The train won't run forever though. Its engine, Aqua, has already been
orbiting for about two years and could be a limiting factor for the
complete satellite constellation. Aura itself, the train's "caboose,"
could last much longer.

"It has enough propellant to last eight to 10 years," Tanner said,
adding that some older Earth-observing satellites have outlived their
designed lifetimes by 12 years or so. "These observatories, in all
aspects, are quite tough."

   =========================

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Message timed: 22:53 on 2004-Jun-10

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