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