NRL POAM III to Measure Ozone into Next Decade

4/20/1998 - 14-98r
Contact: Public Affairs Office, (202) 767-2541

The Naval Research Laboratory's (NRL's) Polar Ozone and Aerosol Monitor III (POAM III) instrument is scheduled for launch on Monday March 23, 1998, as a follow-on to the highly successful POAM II experiment, which provided unique data on ozone depletion in the polar stratosphere.

POAM III, which is sponsored by the Office of Naval Research (ONR) and the DoD Space Test Program, will continue this monitoring of the polar stratosphere and provide valuable information on the way the earth's ozone layer is responding to decreased abundances of chlorine in the atmosphere as a result of restrictions in CFC emissions mandated in the international Montreal Protocol.

POAM III will be placed in the same orbit as POAM II and, thus, will have identical measurement coverage. More sensitive than its predecessor, POAM III will be able to measure deeper into the atmosphere with greater precision. The launch of POAM III will provide a continuation of the unique and important measurements of ozone in the polar regions, begun by POAM II, well into the next decade.

POAM III will be carried aboard the French Space Agency (Centre National d'Etudes Spatiales (CNES)) SPOT-4 satellite (the newest in the series of SPOT remote sensing instruments). SPOT-4 will be launched on an Ariane-4 rocket from the CNES facility in Kourou, French Guiana. (The acronym "SPOT" stands for "Satellite Pour l'Observation de la Terre".)

The POAM instruments are space-based atmospheric sensors that have been developed by NRL to monitor ozone, and other atmospheric constituents that are important to the ozone layer in the Arctic and Antarctic stratosphere (the stratosphere extends from about 6 to 30 miles above the earth's surface). POAM collects detailed stratospheric information by scanning through the atmosphere while it follows the sun as it rises or sets. Each POAM profile of the stratosphere contains information on the abundance of ozone, aerosol particles, and other important atmospheric constituents at a vertical resolution of 1 kilometer.

POAM II was launched in September 1993 on the French SPOT 3 satellite, and operated successfully until the host SPOT satellite failed in November 1996. During this three-year period, POAM II made more than 20,000 measurements of ozone concentrations in the stratosphere in the polar regions, providing unprecedented detail as it monitored the 1993 through 1996 Antarctic ozone holes. POAM II's simultaneous observations of ozone, polar stratospheric clouds, and nitrogen dioxide have allowed scientists at NRL and elsewhere to deliver rich new insightsto the science community.

POAM is particularly well suited to the study of the Antarctic ozone hole because it is the only space-borne instrument to make measurements of the ozone profile over the polar regions on a continuous basis. The ozone hole is a remarkable geophysical phenomenon which results in rapid and severe depletion of the ozone layer over Antarctica in late winter and early spring. Although the detailed meteorological and photochemical processes that produce the ozone hole are unique to Antarctica, ozone depletion in the Arctic has been observed, by POAM and several other instruments, in the last several winters, and chemical ozone loss has also been observed at mid latitudes. According to NRL scientists, this suggests that chemical processes, similar to but on a smaller scale than those taking place in the ozone hole, may also be occurring outside of the Antarctic stratosphere and may have significance for global ozone depletion. This adds increasing emphasis and importance to studies of the Antarctic ozone hole, which is the most clear-cut and extreme manifestation and, therefore, optimum place to study these photochemical processes.

POAM III is an integral component of the middle atmosphere science program being carried out jointly by NRL's Remote Sensing and Space Science Divisions. The objective of the program is to study the photochemistry and dynamics of the middle atmosphere using a combined experimental and theoretical approach. In addition to POAM, the experimental programs include the Millimeter-wave Atmospheric Sounder (MAS), the Ground-based Water Vapor Spectrometer (WVMS) and the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) Information on these experiments can be found on the following web sites:

POAM was fabricated by ThermoTrex Corporation (TTC) of San Diego, CA.

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