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For Release: Nov. 26, 1997

Catherine Watson
(757) 864-6122

Release No. 97-127c (UPDATE W/ LAUNCH DATE CHANGE)

New Satellite to be Launched Nov. 27

Pictures from space often show the Earth covered by clouds. In fact, more than 50 percent of the Earth is covered by clouds at any one time. NASA Langley's latest satellite instrument, the Clouds and the Earth's Radiant Energy System (CERES), will use the vantage point of space to provide global data on the Earth's energy balance and how it is changed by clouds.

"The temperature of the Earth is controlled by the global balance between the amount of sunlight absorbed by the Earth, a heat gain, and the amount of energy radiated back to space at thermal infrared wavelengths, a heat loss. Clouds are the largest factor changing this flow of radiation into and out of the Earth," said Dr. Bruce Wielicki, head of the CERES project.

Thin, high clouds can trap heat emitted by the Earth producing warming. Low, thick clouds can reflect the Sun's energy back into space causing cooling. Scientists need to know how different types of clouds trap or reflect energy, and how much and how often they do it, in order to understand what effects clouds may have on our planet's climate.

"Uncertainties about the way clouds change the energy available to heat and cool the Earth is the largest uncertainty in predicting the magnitude of future climate change caused by increasing greenhouse gases," Wielicki said.

"Clouds change greatly from the equator to polar regions, from day to night, and from land to ocean. Fortunately, satellites allow scientists to observe the complete range of cloud types on the Earth, as well as to measure their behavior and role in the climate system," Wielicki said. "A good example of this type of measurement is to observe the changes in clouds and energy flows which occur during El Nino. The fortuitous timing of the [CERES] launch will allow measurements to be taken both during and after the current major El Nino event."

"[CERES] also will improve the accuracy of solar insolation data used for determining the sites of solar power plants, solar cookers in refuge camps, solar refrigerators, etc. This will happen roughly three to four years after launch," Wielicki said.

CERES, part of NASA's Mission to Planet Earth program, is scheduled for launch Nov. 27 at 3:40 p.m. EST aboard the Tropical Rainfall Measuring Mission (TRMM) observatory. NASA TV will provide live coverage of the TRMM launch from 3:30 - 5:40 p.m. EST. NASA TV is available on GE-2, transponder 9C (C-Band), located at 85 degrees West longitude, with vertical polarization and a frequency of 3880 MHz, and audio at 6.8 Mhz. For more information: TRMM homepage

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