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Clouds exert an enormous influence on our
weather and climate. They are the key element of
Earth’s hydrological cycle, bringing water from
the air to the ground and from one region of the
globe to another. Clouds also dominate the energy
budget of Earth through their influence on the
exchange of solar and thermal energy within the
atmosphere and between the atmosphere,
hydrosphere, land surface, biosphere, and space.
Because clouds have such a large impact on
Earth’s radiation budget, even small changes in
cloud abundance or distribution could alter the
climate more than the anticipated changes in
greenhouse gases, anthropogenic aerosols, or other
factors associated with global change. Changes in
climate that are caused by clouds may in turn give
rise to changes in clouds due to climate: a
cloud-climate feedback. These feedbacks may be
positive (reinforcing the changes) or negative
(tending to reduce the net change), depending on
the processes involved. These considerations lead
scientists to believe that the main uncertainties
in climate model simulations are due to the
difficulties in adequately representing clouds and
their radiative properties.
CloudSat was selected as a NASA
Earth System Science Pathfinder satellite
mission in 1999 to provide observations necessary
to advance our understanding of cloud abundance,
distribution, structure, and radiative properties.
Since 2006, CloudSat has flown the first
satellite-based millimeter-wavelength cloud
radar—a radar that is more than 1000 times more
sensitive than existing weather radars. Unlike
ground-based weather radars that use centimeter
wavelengths to detect raindrop-sized particles,
CloudSat's radar allows us to detect the much
smaller particles of liquid water and ice that
constitute the large cloud masses that make our
weather.
CloudSat was co-manifested with the CALIPSO
(Cloud-Aerosol Lidar and Infrared Pathfinder
Satellite Observations) satellite aboard a Delta
II rocket for its launch on 28 April 2006. In a
series of maneuvers, CloudSat and CALIPSO joined
three satellites already in orbit ( Aqua, PARASOL,
and Aura)
to form a constellation of satellites known as the
A-Train on 1 June 2006. The satellites fly in a
nearly circular orbit with an equatorial altitude
of approximately 705 km. The orbit is
sun-synchronous, maintaining a roughly fixed angle
between the orbital plane and the mean solar
meridian. CloudSat maintains a close formation
with Aqua and a particularly close formation with
CALIPSO, providing near-simultaneous and
collocated observations with the instruments on
these two platforms. Combined data products are in
development using data streams from CloudSat +
Aqua and CloudSat + CALIPSO.
Science leadership for CloudSat is provided by
the Principal Investigator, Prof. Graeme Stephens
of Colorado State University, in cooperation with
the CloudSat Science Team. NASA's Jet Propulsion
Laboratory provides overall project and mission
management and development and implementation of
CloudSat's instrument, the Cloud Profiling Radar.
A more extensive description of CloudSat mission
participants and their roles is given on the Partners
page.
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