* Astronomy

The Jet Propulsion Laboratory-managed satellite named CloudSat is preparing to launch into low-Earth orbit to improve scientists' understanding of clouds and their distribution throughout the atmosphere.

"CloudSat is all about fresh water and trying to understand the movement of fresh water in the Earth's climate and weather system. So it has real implications for every person" - Deborah Vane, the mission's deputy principal investigator from JPL.

Clouds convey fresh water from one spot to another. Without clouds, the world's fresh water supplies would eventually disappear. But there is no way to know on a global scale how much water exists in clouds and how efficient clouds are at converting water vapour into rain or snow.

"If we had a better idea of those reservoirs and how they're controlled, maybe we could do a better job of predicting how they might change" - Deborah Vane.

Clouds also serve dual roles in modulating the Earth's energy balance by both reflecting sunlight into space and blanketing the planet to trap heat.
The data CloudSat collects will be useful in a variety of applications, including informing mathematical models that predict climate change.
When most people think of global warming, they think carbon dioxide and the greenhouse effect.

"But much more important than carbon dioxide is water vapour" - Kenneth Eis, mission data processing centre manager from Colorado State University.

It is a powerful, highly abundant greenhouse gas. And CloudSat will help pin down the distribution of water vapour throughout the atmosphere.
CloudSat is unlike any previously launched satellite because it will not only measure the tops of clouds, but also the bottoms and everything in between.

"If you see just the very top, you don't know anything about what's underneath, (comparing studying cloud tops to observing a fire from an airplane), You see the smoke, you don't see the fire" - Kenneth Eis.

CloudSat will launch along with a satellite named CALIPSO to assume a position with a constellation of Earth-monitoring satellites called the "A-Train." CloudSat, with its radar capabilities, will trace around the Earth about 14 times a day from a spot two minutes behind NASA's Aqua satellite and just 15 seconds ahead of CALIPSO.
Like a fish-finder building a profile of the water under a boat, CloudSat's radar will aim straight down, sending out pulses and measuring reflections in order to piece together a picture of the clouds below.

The new instrument will provide cloud measurements representing a 10 - 20 fold improvement over those currently used.
CloudSat is scheduled to launch from the Vandenberg Air Force Base. Its primary mission will be 22 months, but the team says the radar instrument could last longer than three years.

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