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Mission Overview

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Whole Is Greater Than the Parts
The usefulness of data from CloudSat, CALIPSO and the other satellites of the A-train will be much greater when combined. Observations of the vertical distribution of clouds and aerosols along with other A-train measurements of aerosols, clouds and the amount of radiation received from the sun and emitted by the Earth will allow scientists to better understand the impact of aerosols on climate, and how sources of local pollution affect air quality. The combined measurement set will also provide new insight into the distribution and evolution of clouds over the globe that will lead to improvements in weather forecasting and climate prediction. The data will be used to study interactions between aerosols and clouds that may change the amount of sunlight they reflect and absorb, or enhance or suppress precipitation: subjects of current scientific debate.

artist's concept of CloudSat and CALIPSO orbiting Earth along with other satellites
Image above: Artist's concept of CloudSat, CALIPSO and the A-Train monitoring Earth together. Image credit: NASA
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The near-simultaneous A-train observations will be achieved through innovative, high-precision satellite formation flying. For the first time, five satellites will be maintained in orbit within 15 minutes of the lead and trailing spacecraft while traveling at over 15,000 miles per hour. The CloudSat and CALIPSO satellites will be controlled to an even finer requirement, within 15 seconds of each other, so that both instrument suites will view the same cloud area at nearly the same moment.

Like a physician using sophisticated diagnostic tools to examine the human body, CloudSat and CALIPSO carry unique, active and complementary instrumentation to acquire profile data on clouds and aerosols. Most other satellite experiments passively observe the atmosphere by measuring the amount of reflected sunlight or energy emitted by the atmosphere or Earth. These measuring techniques are unable to accurately determine the vertical structure of clouds and aerosols. CloudSat and CALIPSO will probe the atmosphere by transmitting pulses of electromagnetic energy and measuring the portion scattered back to the instrument. CloudSat's Cloud Profiling Radar uses microwave energy to observe cloud particles and determine the mass of water within clouds. The much shorter wavelengths of visible light emitted by CALIPSO's lidar allow measurements of aerosols and thin cirrus ice clouds invisible to the CloudSat radar. CALIPSO can even detect thin clouds invisible to the human eye. Additional information on cloud properties will be derived from the passive instruments on CALIPSO. Together, the instruments provide essential new data on how clouds and aerosols heat or cool the atmosphere that are needed to improve weather and climate models.

The Earth Observing Satellites will do far more than acquire a three-dimensional portrait of the planet. They will create a wide, detailed, evolving global mural of Earth's interactive systems. And just as space-borne observations cross many geographic boundaries, the CloudSat and CALIPSO missions would not be possible without their international mix of organizational partners and scientists from the United States, Canada, Japan, and Europe.