New Space-borne Instrument to Track Greenhouse Gases, Ozone Destroyers, and Other Pollutants
Launched! HIRDLS is now in orbit. The Aura spacecraft blasted off at 4:01:59 a.m. Mountain Time (6:01:59 Eastern, 3:01:59 Pacific) on Thursday, July 15, and entered Earth orbit about one hour later.
July 7, 2004
BOULDER—A powerful new instrument heading to space this Saturday is expected to send back long-sought answers about greenhouse gases, atmospheric cleansers and pollutants, and the destruction and recovery of the ozone layer. Only a cubic yard in size but laden with technical wizardry, the High-Resolution Dynamic Limb Sounder (HIRDLS) will measure a slew of atmospheric chemicals at a horizontal and vertical precision unprecedented in a multi-year space instrument.
Scientists at the National Center for Atmospheric Research (NCAR), University of Colorado, and University of Oxford developed HIRDLS (pronounced "hurdles") with funding from NASA and United Kingdom sources. The U.S. space agency plans to launch the 21-channel radiometer along with three other instruments July 10 aboard its Aura satellite from Vandenberg Air Force Base in California.
HIRDLS will capture the chemistry and dynamics of four layers of the atmosphere that together span a region 8 to 80 kilometers (5 to 50 miles) above Earth’s surface: the upper troposphere, the tropopause, the stratosphere, and the mesosphere.
Using infrared radiation as its yardstick, the radiometer will look through Earth’s atmosphere toward the planet’s limb, or edge. It will find and measure ten different chemical species, characterize airborne particles known as aerosols, and track thin cirrus clouds, all at a vertical resolution of half a kilometer (a third of a mile) and a horizontal resolution of 50 kilometers (30 miles). The signal-to noise ratio is one tenth that of previous detectors.
"The angular resolution of the instrument’s mirror position is equivalent to seeing a dime eight miles away," says principal investigator John Gille, of NCAR and the University of Colorado.
A few questions HIRDLS data will answer
What are the concentrations of the primary greenhouse gases and
their height in the atmosphere?
Why does the tropopause exist and what is its role in conveying
gases from the troposphere into the stratosphere, especially in
Why is the stratosphere, historically dry, now getting wetter?
How much ozone is sinking from the stratosphere into the upper
Scientists also expect to see clearly for the first time the dynamic processes that cause water vapor filaments and tendrils to break off and mix with other gases in the troposphere.
Good and bad ozone at different altitudes
At 50 kilometers (30 miles) above the ground, ozone is good: it blocks dangerous ultraviolet radiation and prevents it from harming life and materials at ground level. At 10 kilometers (6 miles), ozone is a greenhouse gas, which is good because the natural greenhouse effect is necessary to warm the planet, but bad if the warming continues to increase at too rapid a rate. At 5 kilometers (3 miles), ozone is a source of the hydroxyl radical, which cleanses the atmosphere of pollutants. But at ground level, ozone is a primary pollutant in smog, causing respiratory problems and damaging trees and crops.
NCAR's primary sponsor, the National Science Foundation, provided additional support for the research that made HIRDLS possible.
Related sites on the World Wide Web
For more information on HIRDLS, see
The National Center for Atmospheric Research and UCAR Office of Programs are operated by UCAR under the sponsorship of the National Science Foundation and other agencies. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any of UCAR's sponsors.