Scientific Colloquium
October 13, 2006

"Ultraviolet Observations of our Changing Planet"

Two Goddard scientists in the late 60's developed the Backscatter Ultraviolet (BUV) instrument to study the Earth's ozone layer from satellites. The first BUV instrument was launched on Goddard's Nimbus-4 satellite in April 1970. More than a dozen instruments of increasing sophistication have been launched in the past 36 years on NASA, NOAA, Japanese, Russian and ESA satellites and many more are currently in development. Originally designed to measure ozone density near 40 km, the buv instruments have played a central role in monitoring changes in the Earth's ozone layer and other trace gases down to the ground. Maps of the Antarctic ozone hole produced by Nimbus-7 TOMS in 1985 convinced the public and policy makers around the world on the seriousness of the ozone depletion problem leading to International treaties to phase out ozone destroying substances.

Improvements in retrieval techniques have allowed these instruments to measure sulfur dioxide injected into the atmosphere in volcanic eruptions, track   regional transport of smoke from biomass burning, and observe inter-continental transport of mineral dust lofted up by winds from the Earth's major deserts. Improvements in the instrument sensitivity in the last decade have made it possible to observe boundary layer pollutants, such as NO2 and SO2, as well as several trace gases (HCHO, CHOCHO, BrO) involved in air quality chemistry. A journey through the history of the buv measurements provides a fascinating glimpse into the history of a field that NASA initiated as "curiosity-driven research", which nonetheless altered the course of a multi-billion dollar global industry and has forever altered our perception about the fragility of our environment.

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