To commemorate Earth Day, Atmospheric Sciences at NASA Langley, marking its
twenty-fifth anniversary as a major field of study this year, highlights
research contributions that ultimately have increased the awareness of how
human activities impact the atmosphere.

After a quarter century of investigating atmospheric processes from the air,
land, sea and space, NASA Langley researchers have developed new
technologies and made scientific discoveries that revolutionized how
scientists study and understand Earth’s atmosphere. A list of
accomplishments and new research of Langley’s major space-based instruments
and multi-platform field experiments follows:

A First in Atmospheric Sensing

Langley researchers were the first to develop and operate a space-based
atmospheric LIDAR (Light Detection and Ranging – an atmospheric sensing
instrument). The Lidar In-Space Technology Experiment (LITE) instrument was
flown on the Space Shuttle Discovery in 1994, proving that space-based lidar
measurements could offer invaluable data unavailable by other means. Among
the many accomplishments of LITE, these data provided the first highly
detailed global view of the vertical structure of cloud and aerosols from
the Earth’s surface through the middle stratosphere as well as sensitive
observations of the distribution of dust, smoke and other aerosols. The
success of the LITE instrument paved the way for a new lidar-based
satellite, Pathfinder Instruments For Cloud and Aerosol Spaceborne
Observations-Climatologie Etendue des Nuages et des Aerosols (PICASSO-CENA),
developed by Langley researchers that is scheduled to launch in 2004.

Documenting Environmental Progress

September 2001 marks the HALOE (Halogen Occultation Experiment) instrument’s
tenth year in orbit aboard the Upper Atmosphere Research Satellite with
flawless operation. After a decade of measuring ozone and trace gases in the
upper atmosphere, HALOE tells an environmental success story. It is the only
space-based instrument that monitored the reduction and leveling off of
chlorine in the stratosphere due to reduced chlorofluorocarbon (CFC)
production. HALOE has also improved the understanding of ozone depletion in
the stratosphere.

Monitoring Volcanic Eruptions and Ozone

The Stratospheric Aerosol and Gas Experiment II (SAGE II) mission has
monitored aerosol, ozone and other trace gases from space since 1984. A
major contribution of this instrument is the long record of ozone data it
has provided. These data have proven to be an invaluable asset to the United
Nations Environment Program for assessing ozone trends. Other SAGE II data
gave researchers a better understanding of the influence human activities
have on aerosols in the atmosphere as well as the long-term global climatic
effects of the 1991 Mt. Pinatubo volcanic eruption. The SAGE III mission
will build upon the success of SAGE II with a launch scheduled during 2001.

Understanding the Earth’s Lower Atmosphere

Tropospheric processes have wide-ranging effects within the atmosphere, so a
detailed understanding of these is essential for an accurate picture of
global climate change. So important is the understanding of these processes
that the National Academy of Sciences established the Global Tropospheric
Chemistry Program on behalf of the United States’ effort in an international
research program designed to study the troposphere. The Global Tropospheric
Experiment (GTE), managed by Langley, is NASA’s contribution to this

The GTE is a program of aircraft-based experiments dedicated to improving
the knowledge of global tropospheric chemistry and its implications for the
biosphere, climate, and stratosphere. Past GTE missions provided
measurements about ozone production and loss in the remote troposphere, a
baseline against which to measure future pollution impacts on the
troposphere, and new information for climate models. The latest GTE mission,
the Transport and Chemical Evolution over the Pacific (TRACE-P) experiment,
is currently taking place in the western Pacific off the coast of Asia and
will study the impact of a major industrial revolution on the composition
and chemistry of the atmosphere.