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Tech

Satellites to capture 3-D images of clouds

Data from two satellites will lead to a better understanding of the way clouds and aerosols influence weather and climate   

January 11, 1999
Web posted at: 11:00 AM EST

By Environmental News Network staff

(ENN) -- In an attempt to dramatically improve weather forecasting, Colorado State University will team with NASA's Jet Propultion Laboratory and Ball Aerospace of Boulder to launch a satellite that can provide the first three-dimensional pictures of clouds.

Under the direction of Graeme Stephens, professor of atmospheric science, the CloudSat spacecraft will produce detailed, three-dimensional images of vertical cloud structures -- a missing component in weather forecasting and climate change models. The satellite will launch in March 2003 on its two-year mission.

Colorado State technology and instrumentation will also play an important role in a second NASA satellite mission that will study aerosols and thin clouds.

The PICASSO-CENA spacecraft will carry a spectrometer that measures reflected sunlight in part of the visible spectrum. The so-called oxygen A-band spectrometer, being built by Ball Aerospace, is based on theory and experimentation developed by Colorado State atmospheric science faculty and graduate students.

Stephens, a specialist in remote sensing, climate change and atmospheric energy transfer and hydrology, is principal investigator for CloudSat, a $145 million, five-year project. Much of the technology and theory driving the effort was developed at Colorado State, he said, with students involved in all aspects of the ongoing mission.

NASA will provide some $119 million of the estimated cost, with the remainder of the $145 million coming from the U.S. Air Force, the Canadian Space Agency and the U.S. Department of Energy.

Data from the two satellites, said Stephens, will lead to a better understanding of the way clouds (small water and ice particles suspended in the atmosphere) and aerosols (small dust particles) influence weather and climate.

"One of the most significant limitations in terms of weather forecasting, and climate prediction in particular, is our inability to predict the formation of clouds in the atmosphere," he said. "We don't have information on three-dimensional vertical structures of clouds.

"What CloudSat and PICASSO-CENA do is provide critical information that allows us to evaluate and predict cloudiness, both as part of weather systems and as part of a longer-range climate system. Our inability to predict cloudiness is the single biggest difficulty in improving predictions of the effects of the build up of greenhouse gases on the Earth's climate."

"CloudSat uses a different radar, several orders of magnitude more sensitive than weather radar, that allows us to see practically all the water droplets and ice crystals in clouds not normally detected by weather radar," Stephens said. "It's analogous to a CAT scan. It allows us to look at the whole structure of a cloud and thus understand how they form and evolve. We haven't been able to do that at present because current satellites just provide observations of the top surface of clouds."

Air Force telemetry systems are expected to receive nearly seven gigabits of data daily from CloudSat. This information will be processed by Colorado State's Cooperative Institute for Research in the Atmosphere, which already performs similar functions for satellites currently in orbit.

A unique feature of the CloudSat spacecraft, to be built by Ball Aerospace, is that it will fly in formation with another satellite, ICESat, which carries a radar-like instrument called lidar that uses a visible light laser to detect an object's position and range. Together, Stephens said, the two satellites will provide "a virtual platform of radar, lidar and A-band spectrometer."

In the past year, Colorado State's atmospheric science department has formed a cooperative research center with NASA's Goddard Space Flight Center called the Center for Earth and Atmospheric Studies, under Stephen's direction. The CloudSat and PICASSO-CENA missions will form a foundation as the center grows and develops planned partnerships with two other NASA centers, the Jet Propulsion Laboratory and Langley Research Center.

For more information, contact Dave Weymiller, Colorado State, (970)491-6432, email: Dweymiller@vines.colostate.edu.

Copyright 1999, Environmental News Network, All Rights Reserved

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