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Aura's instruments
Posted: July 7, 2004

High Resolution Dynamics Limb Sounder

HIRDLS is an infrared limb-scanning radiometer measuring trace gases, temperature, and aerosols in the upper troposphere, stratosphere, and mesosphere.

The instrument will provide critical information on atmospheric chemistry and climate. Using vertical and horizontal limb scanning technology, HIRDLS will provide accurate measurements with daily global coverage at high vertical and horizontal resolution. The University of Colorado, the National Center for Atmospheric Research (NCAR), Oxford University (UK) and Rutherford Appleton Laboratory (UK) designed the HIRDLS instrument. Lockheed Martin built and integrated the instrument subsystems. The National Environmental Research Council funded the United Kingdom participation.

HIRDLS Contributions to Understanding Stratospheric Ozone
The largest ozone depletions occur in the polar winter lower stratosphere. HIRDLS will retrieve high vertical resolution daytime and nighttime ozone profiles in this region.

HIRDLS will measure CFCs, NO2, and HNO3, gases that play a role in stratospheric ozone depletion. Although international agreements have banned CFC production, CFCs are long-lived and will remain in the stratosphere for several more decades. By measuring profiles of the long-lived gases, from the upper troposphere into the stratosphere, HIRDLS will improve our ability assess the transport of air from the troposphere into the stratosphere.

HIRDLS Contributions to Understanding Air Quality
HIRDLS will measure ozone, nitric acid, and water vapor in the upper troposphere and lower stratosphere. With these measurements, scientists will be able to improve estimates of the amount of stratospheric air that descends into the troposphere and will allow us to separate natural ozone pollution from man-made sources.

HIRDLS Contributions to Understanding Climate Change
HIRDLS will measure water vapor and ozone, both important greenhouse gases. The instrument is also able to distinguish between aerosol types that absorb or reflect incoming solar radiation. HIRDLS will be able to map high thin cirrus clouds that reflect solar radiation.

Microwave Limb Sounder

MLS is a limb scanning emission microwave radiometer. MLS measures radiation in the Gigahertz (GHz) and Terahertz (THz) frequency ranges (millimeter and sub-millimeter wavelengths). Aura's MLS is a major technological advance over the MLS flown on the Upper Atmosphere Research Satellite (UARS). MLS will measure important ozone-destroying chemical species in the upper troposphere and stratosphere. In addition, MLS has a unique ability to measure trace gases in the presence of ice clouds and volcanic aerosols. NASA's Jet Propulsion Laboratory (JPL) developed, built, tested, and will operate MLS.

MLS Contributions to Understanding Stratospheric Ozone
Aura's MLS will continue the ClO measurements and provide first time global HCl measurements. These measurements will inform us about the rate at which stratospheric chlorine is destroying the ozone. MLS will also provide the first global measurements of the stratospheric hydroxyl (OH) and hydroperoxy (HO2) radicals that are part of the hydrogen catalytic cycle for ozone destruction. In addition, MLS will measure vertical profiles bromine monoxide (BrO) for the first time, a powerful ozone-destroying radical. BrO has both natural and man-made sources.

MLS measurements of ClO and HCl will be extremely helpful to scientists studying the polar regions. The HCl measurements tell scientists how stable chlorine reservoirs are converted to the ozone destroying radical, ClO. Since the Arctic stratosphere may now be at a threshold for more severe ozone loss, Aura's MLS data will be especially important.

MLS Contributions to Understanding Air Quality
MLS measures carbon monoxide (CO) and ozone in the upper troposphere. CO is an important trace gas that can indicate the exchange of air between the stratosphere and troposphere. CO is also a tropospheric ozone precursor and its appearance in the upper troposphere can reveal strong vertical transport from pollution events.

MLS Contributions to Understanding Climate Change
A critical unanswered question in understanding climate is what controls the abundance of water vapor in the upper troposphere and lower stratosphere (UTLS). MLS's measurements of UTLS water vapor and temperature as well as upper troposphere ice content, will be used to reduce the uncertainty in this critical climate forcing. MLS also measures greenhouse gases such as ozone and N2O in the upper troposphere, and water measurements.

Ozone Monitoring Instrument

OMI is a nadir viewing spectrometer that measures solar reflected and backscattered light in a selected range of the ultraviolet and visible spectrum. The instrument's 2600 km (1,616 mile) viewing swath is perpendicular to the orbit track, providing complete daily coverage of the sunlit portion of the atmosphere. OMI is Aura's primary instrument for tracking global ozone change and will continue the high quality column ozone record begun in 1970 by Nimbus-4 BUV.

OMI has a broader wavelength range and better spectral resolution than the Total Ozone Mapping Spectrometer (TOMS) instruments, which preceded Aura. OMI will also measure column amounts of trace gases important to ozone chemistry and air quality. OMI will map aerosols and estimate ultraviolet radiation reaching the Earth's surface. OMI's horizontal resolution is about four times greater than TOMS.

The Netherlands Agency for Aerospace Programs (NIVR) and the Finnish Meteorological Institute (FMI) contributed the OMI instrument to the Aura mission. The Netherlands companies, Dutch Space and TNO-TPD, together with Finnish companies, Patria, VTT and SSF, built the instrument.

OMI Contributions to Understanding Stratospheric Ozone
OMI will continue the 34-year satellite ozone record of SBUV and TOMS, mapping global ozone change. OMI data will support congressionally mandated and international ozone assessments. Using its broad wavelength range and spectral resolution, OMI scientists will have more accurate measurements to resolve the differences among satellite and ground-based ozone measurements.

OMI Contributions to Understanding Air Quality
OMI will also measure the atmospheric column of radicals such as nitrogen dioxide (NO2) and chlorine dioxide (OClO). Tropospheric ozone, nitrogen dioxide, sulfur dioxide, and aerosols are four of the U.S. Environmental Protection Agency's six criteria pollutants. OMI will map tropospheric columns of sulfur dioxide and aerosols. OMI measurements will be combined with information from MLS and HIRDLS to produce maps of tropospheric ozone and nitrogen dioxide.

OMI will also measure the tropospheric ozone precursor, formaldehyde. Scientists will use OMI measurements of ozone and cloud cover to derive the amount of ultraviolet radiation (UV) reaching the Earth's surface. The National Weather Service will use OMI data to forecast high UV index days for public health awareness.

OMI Contributions to Understanding Climate Change
OMI tracks dust, smoke and industrial aerosols in the troposphere. OMI's UV measurements allow scientists to distinguish reflecting and absorbing aerosols and will help improve climate models.

Tropospheric Emission Spectrometer

TES is an imaging Fourier Transform Spectrometer observing the thermal emission of the Earth's surface and atmosphere, night and day. TES will measure tropospheric ozone directly and other gases important to tropospheric pollution with very high horizontal resolution. TES has a higher spatial resolution than OMI, but with less coverage. Satellite tropospheric chemical observations are difficult to make due to the presence of clouds. To overcome this problem, TES was designed to observe both downward (in the nadir) and horizontally (across the limb). This observation capability provides measurements of the entire lower atmosphere, from the surface to the stratosphere. NASA's JPL developed, built, tested, and will operate TES. The TES primary objective is to measure trace gases associated with air quality.

TES Contributions to Understanding Stratospheric Ozone
TES limb measurements extend from the Earth's surface to the middle stratosphere. As a result, TES's high resolution spectra will allow scientists to make measurements of some additional stratospheric constituents that compliment the HIRDLS and MLS measurements.

TES Contributions to Understanding Air Quality
TES will measure the distribution of gases in the troposphere. TES will provide simultaneous measurements of tropospheric ozone and key gases involved in tropospheric ozone chemistry, such as CH4, HNO3 and CO. TES is unique because its the first space-based instrument designed with tropospheric profiling in mind. TES data will be used to improve regional ozone pollution models.

TES Contributions to Understanding Climate Change
TES will measure tropospheric water vapor, methane, ozone and aerosols, all of which are relevant to climate change. Additional gases important to climate change can be retrieved from the TES spectra.