CU-Boulder Satellite Instrument to Provide New Details on Ozone

Just after 3 a.m. on July 10, University of Colorado at
Boulder researcher John Gille expects to watch a new NASA satellite
blast into orbit from the dark California coastline on a mission to
study Earth’s protective ozone layer, climate and air quality changes
with unprecedented detail.

Gille, principal investigator on the satellite’s High
Resolution Dynamics Limb Sounder (HIRDLS) instrument, said he and
his sleep-deprived colleagues will probably only get to watch the
rocket for a few moments before it disappears into a thick deck of
clouds that typically settles over the area this time of year.

The irony isn’t lost on Gille, who’s been at work on the
instrument since 1988. “Writing about clouds in a meteorological
journal, a scientist once said, ‘There’s no way to deal with these
troublesome objects,’ ” he laughed.

Surface ozone pollution and air quality deterioration —
byproducts of agricultural burning, deforestation, urban activity
and industry — are increasing worldwide. Questions remain about the
recovery of the protective ozone layer and the role of chemistry in
climate change. HIRDLS and three other instruments on NASA’s AURA
satellite are designed to address these questions in detail.

HIRDLS is an international collaboration between scientists
and engineers in the U.S. and Britain. Gille is HIRDLS U.S.
principal investigator, and along with his Oxford University
counterpart he is responsible for the overall success of the
instrument, including design, testing, collection and use of data
for scientific purposes.

At CU-Boulder, Gille is an adjoint professor in the Program
in Atmospheric and Oceanic Sciences and senior research associate at
the Center for Limb Atmospheric Sounding. “Limb” is the astronomical
term for the edge of a planet and its atmosphere.

“Unlike the satellite images you see during TV weather
forecasts, which are looking straight down at the Earth, our
instrument is looking off toward the horizon,” Gille said. “We look
at the horizon from orbit, scanning up and down for a profile view.”

The profile gives scientists insight into radiation,
temperature and distribution of gases at different levels in the
atmosphere. The data is then used to study the ozone layer, climate
change and interaction between layers of the atmosphere.

HIRDLS will scan the mid- to upper-troposphere and the
tropopause, the boundary region between the troposphere and the
stratosphere. The troposphere extends upward from the Earth’s
surface to about 10 miles high at the equator and five miles high at
the North and South poles. The stratosphere, which contains trace
gases as well as the radiation-absorbing ozone layer, lies on top of
the troposphere.

HIRDLS is expected to present a much clearer picture of
whether the ozone layer is recovering, as well as the distribution
of greenhouse gases that influence climate.

“HIRDLS has much finer horizontal resolution than we’ve ever
had before,” Gille said. “We can send commands to the satellite to
zoom in and get readings with resolutions as fine as 30 to 60 miles,
and a vertical resolution of 1,500 feet. Also, the HIRDLS detectors
are up to 10 times more sensitive than similar instruments that have
flown in the past.”

The instrument is designed to last much longer in orbit than
its predecessors, too. Thanks to an onboard mechanical refrigerator
built by Ball Aerospace and Technologies Corp. of Boulder,
scientists expect it will last longer than five years. It’s hoped
that longer-term trends can be predicted with the volume of data
that will be collected.

The HIRDLS project began in 1988. Since that time, Gille and
his research team at the university have led a collaborative effort
to design and build the instrument with scientists and engineers at
Oxford University in the United Kingdom, the National Center for
Atmospheric Research in Boulder, the University of Washington and
Lockheed Martin in Palo Alto, Calif.

Gille expects many of those who have worked on HIRDLS during
the past 16 years to make the trip to Vandenburg Air Force Base,
north of Santa Barbara, Calif., for the July 10 AURA launch at 3:01
a.m. Pacific Daylight Time.

For more information about the HIRDLS instrument visit
http://www.eos.ucar.edu/hirdls/. For more information about
CU-Boulder atmospheric research visit http://paos.colorado.edu/ and
click on “Related Links.”