Brian Dunbar 
Headquarters, Washington, D.C.                          December 5, 1991
(Phone:  202/453-1547)
 
Jessie Katz 
Goddard Space Flight Center, Greenbelt, Md.
(Phone:  301/286-5566)

James Wilson
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone:  818/354-5011)

RELEASE:  91-199

DATA ILLUSTRATES LINK BETWEEN CHLORINE, OZONE DEPLETION 

	Early results from NASA's Upper Atmosphere Research Satellite 
(UARS) have confirmed the link between the presence of chlorine 
monoxide and the depletion of ozone in Earth's upper atmosphere.  

	The UARS, launched by Space Shuttle Discovery on Sept. 12, 1991, is 
studying the upper atmosphere to better understand the processes at work 
in this vital region of the Earth's environment.  The early results indicate 
that UARS is a powerful new tool for detecting and tracking ozone 
depletion and the factors that cause it, officials at the Goddard Space Flight 
Center, Greenbelt, Md., said today.

	Data from the satellite have provided the first global-scale picture of 
the distribution of chlorine monoxide in the lower stratosphere.  Chlorine 
monoxide is one of the main chemical species involved in the depletion of 
the Earth's ozone layer and is the dominant constituent causing the 
Antarctic ozone hole.

	UARS has helped show that the more chlorine monoxide present, the 
less ozone will be observed.  Chlorine monoxide, in the upper atmosphere, 
results from the breakdown of the man-made chlorofluorocarbons by the 
Sun's ultraviolet radiation.  UARS has observed high chlorine monoxide 
over Antarctica, while simultaneously measuring the ozone depletion that 
accompanies it.  These data confirm the relationship in the upper 
atmosphere between the two chemicals.

	The relationship between high concentrations of chlorine monoxide 
and low concentrations of ozone previously have been made from the 
ground and by NASA ER-2 aircraft.  However, the ground and aircraft 
measurements have been conducted over a much smaller geographical area 
than is now being done by UARS.  

	The UARS data examined to date show that extremely high amounts 
of chlorine monoxide (greater than about one molecule of chlorine 
monoxide for every 1 billion "air" molecules) occur only where ozone is 
severely depleted. Those data also show great variation of chlorine 
monoxide levels within the Antarctic hole and are expected to improve 
scientific understanding of the ozone depletion process occurring there as 
well as at other places on the globe.

	These first results from the UARS were obtained with the Microwave 
Limb Sounder (MLS), one of the 10 scientific instruments aboard the 
satellite.  MLS detects microwave radiation emitted from chlorine 
monoxide, ozone, sulfur dioxide and water vapor in the atmosphere.  That 
radiation is then analyzed to produce chemical concentration and 
temperature data at altitudes throughout the upper atmosphere over nearly 
the entire Earth as the UARS spacecraft orbits at an altitude of 363.5 miles.

	The MLS also is seeing the effects of the large eruption of Mount 
Pinatubo in the Philippines on June 15, 1991.  The volcano injected huge 
amounts of sulfur dioxide into the stratosphere, the remnants of which 
appear to the MLS as a band of high sulfur dioxide concentrations over the 
tropics.  Aerosol particles formed from volcanic sulfur dioxide could lead to 
significant ozone loss in the vicinity of the plume.  

	Nothing comparable to the very high chlorine monoxide 
concentration over Antarctica has as yet been detected by the UARS in the 
volcanic plume.  The satellite will maintain a watch for such effects as the 
volcanic plume spreads northward during the next several months and 
gradually subsides.  Patches of enhanced sulfur dioxide also have been 
detected in the southern hemisphere and are probably from the smaller 
Mount Hudson eruption in Chile in August 1991.

	All instruments aboard the UARS have been activated and are 
operating successfully.  In addition to chlorine monoxide, ozone and sulfur 
dioxide, the satellite instruments also have measured nitric oxide, water 
vapor, stratospheric temperature, energetic particles that cause the aurora, 
and the solar ultraviolet spectrum.  All spacecraft systems are meeting or 
exceeding specifications, Goddard officials said.  Many additional 
measurements are expected as the instruments complete their scheduled 
validation testing.

	The Microwave Limb Sounder was developed and is operated on the 
UARS by NASA's Jet Propulsion Laboratory (JPL), Pasadena, Calif., in 
collaboration with United Kingdom groups at Heriot-Watt University, 
Edinburgh University and the Rutherford-Appleton Laboratory.  Dr. Joe W. 
Waters of JPL is Principal Investigator.

	UARS, the first major project of NASA's Mission to Planet Earth 
program, will provide scientists with the first comprehensive data set on 
the chemistry, wind velocities and energetics of Earth's upper atmosphere.  
UARS is managed and operated by the Goddard center for NASA's Office of 
Space Science and Applications, Washington, D.C.  

- end -

NOTE TO EDITORS/NEWS DIRECTORS:  Satellite images of ozone levels 
are available to accompany this release and may be obtained by calling the 
Goddard Space Flight Center Public Affairs Office (301/286-5566) or 
(301/286-7512).  These images also are available to media representatives 
from the NASA Headquarters Audio Visual Branch by calling (202/453-
8373).  Headquarters image numbers are:

B&W                                   Color
91-H-884                           91-HC-783
91-H-885                           91-HC-784
91-H-886                           91-HC-785