Stretching 1,864 miles (3,000 kilometers) nose to tail, the parade of satellites will follow an orbit 438 miles (705 kilometers) up and will cover ground at more than 15,000 miles an hour (24,000 kilometers an hour).
The satellites, with their various detectors and imagers, will follow one another so fast that at any given time they will each effectively be examining the same sliver of atmosphere simultaneously in different ways.
The lead satellite, launched in 2002, is a water- and energy-observing platform called Aqua.
Last in line is Aura, an atmospheric chemistry-measuring package that NASA launched last year.
The fourth bead in the string is Parasol, a French platform launched in 2004, carrying instruments to measure aerosols and clouds.
CloudSat and CALIPSO are now maneuvering to fall in line after Aqua and will fly only 15 seconds apart.
A big benefit of the system, and of CloudSat in particular, is likely to be improved accuracy in long-range climate-change models.
Early computer climate models were fuzzy and divided the Earth into uniform patches hundreds to thousand of miles wide. Individual clouds were not visible.
"Now it's down to a few miles, but the models still really don't do a very good job handling clouds," Stephens said.
"They make their clouds based on what we think are first principles of physics at work."
That, he said, is just a fancy way to describe informed guesswork.
Clouds matter a lot, he added, because clouds and rain are among the leading agents for moving both water and energy around in the atmosphere.
CloudSat, he said, "lets us say, basically, here is what the real world is doing."
Better Weather Prediction
While hurricane-hunting aircraft and other instrument platforms can fly through storms and gather important information one cloud at a time, CloudSat will be able to get 300,000 cloud profiles or "ribbons of data" daily, scientists say.
"This is a leap forward in climate prediction as well as weather prediction," said Deborah Vane of NASA's Jet Propulsion Laboratory, deputy principal investigator of CloudSat.
(See National Geographic Magazine's "Forecasting the Chaos of Weather.")
The A-Train's data will be merged with information from other satellites to keep an eye on Earth's climate.
On February 14, a Minotaur rocket put a hundred-million-U.S.-dollar string of six small, identical satellites into low Earth orbit to measure the vertical distribution of water vapor in the atmosphere.
The satellite string is a joint effort by NASA and agencies in Taiwan.
The satellites will swap data with higher orbiting global-positioning satellites when their signals take a path that grazes the Earth.
The bending of the signals as they skim through the atmosphere to reach six higher satellites will reveal water vapor distribution, density, temperature, and ionization, data now gathered by weather balloons but rarely obtained over much of the Earth.
Impressive as it all is, there is always room for improvement, said Stephens, CloudSat's principal investigator.
In coming years he hopes to see even better satellites that can measure where the clouds and rain are thickest as well as which way and how fast the twisting winds inside storms are blowing.
"That would be incredible," he said.
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