THE BIG SNIFF.

Smog now spreads from continent to continent. Man is trying to restore the health of the Earth's life-sustaining ozone shield by curtailing some industrial activities, only to find that he's hurting his own cause by what he's doing elsewhere. Greenhouse gases — a lot are man-made but some are from nature — are warming the lower atmosphere and changing the climate. Discovering just how much good news and bad news there is for Earth's atmosphere — and where it's coming from — is the goal for Aura, the third spacecraft in the Earth Observing Satellite series of the U.S. National Aeronautics and Aviation Administration (NASA). Managed by NASA's Goddard Space Flight Center, the EOS trio is an unprecedented effort to monitor global climatic change on land, sea and in the atmosphere.