NASA Mission's goal: understanding clouds

The two spacecraft will be launched this week.
SCRIPPS HOWARD NEWS SERVICE
FORT COLLINS, Colo. -- Graeme Stephens paints pictures of clouds as a hobby; as lead scientist of NASA's $217 million CloudSat mission, he leads an effort to depict nature's mercurial dealers of water in unprecedented detail.
Such understanding will help improve weather forecasts, better understand hurricane dynamics and improve the ability of climate models to predict future global warming, Stephens said.
CloudSat and its sister NASA craft, the $298 million joint NASA-French space agency-built CALIPSO, are scheduled for launch Friday, nearly three years after NASA and legions of atmospheric scientists originally hoped. Stephens described himself as "numb" at the prospect of an actual launch.
Both spacecraft share a single nose cone on a Boeing Delta II rocket awaiting liftoff at California's Vandenberg Air Force Base, and both will be a part of NASA's "A-Train" of Earth-observing satellites already racing about the planet at an altitude of 438 miles and a speed of about 17,000 mph.
The new cloud-observing "cars" will join NASA's Aqua and Aura and France's PARASOL satellites on missions that would last at least two years for CloudSat and at least three years for CALIPSO.
Stephens' talent with paint brought about the rare instance of a NASA mission's lead scientist and its creator of cool images being the same guy. The distinguished professor of atmospheric science at Colorado State University combined his vocation and avocation in describing what CloudSat will do.
What's not known
Scientists' knowledge of clouds is narrow, he said. They have no idea how cloud layering works on a global scale, nor what fraction of clouds produces rain.
"We've not been able to place these brush strokes into the context of a wider canvas," Stephens said, and CloudSat, with CALIPSO, will do that.
CloudSat's radar is 1,000 times more sensitive than typical weather radar and is the best ever to fly, period, mission leaders said.
Unlike typical satellite imagery, which sees only cloud tops, CloudSat will peer straight through clouds and measure the amount and distribution of water at 500-meter intervals.
On CALIPSO, the Ball-built lidar instrument uses laser pulses fired 20 times a second to determine vertical distribution of ice crystals as well as fine atmospheric particles, or aerosols, on which the water droplets of clouds form. Its vertical accuracy is about 30 meters, said Mark LaPole, Ball's program manager on the lidar instrument.