NASA: Pretty Post-Shuttle Launch Clouds Not Likely Tonight

CAPE CANAVERAL, Fla. ? NASA's planned launch of the space shuttle Endeavour tonight isn't likely to form beautiful trails of glowing clouds like those of previous liftoffs, weather experts at Kennedy Space Center (KSC) said.

NASA's June space shot of Atlantis produced one such striking display of the noctilucent -- or night-shining -- clouds, as well as with the launch of the Mars-bound Phoenix spacecraft last weekend. Weather experts here at KSC, however, aren't crossing their fingers for a rare appearance of the clouds after shuttle Endeavour launches at 6:36 p.m. EDT (2236 GMT) tonight.

"I'd be surprised to see noctilucent clouds after this launch," said John Madura, KSC's weather office manager. "We'll see the standard rocket exhaust plume and that may be pretty, but we probably won't see the clouds."

But Tim Garner, a spaceflight meteorologist at NASA's Johnson Space Center (JSC) in Houston, Texas is more optimistic about seeing the rocket-induced clouds 10 to 20 miles (16 to 32 kilometers) above Earth.

"The launch is so close to sunset, I think we have a decent shot at seeing some," Garner said. "The clouds will be diffuse, but we'll have a good lighting angle."

Cloudy recipe

Madura explained that forming the glowing clouds from rocket exhaust follows a sensitive recipe: Made mostly of water, the exhaust plume must freeze into ice crystals and reflect sunlight just before sunrise or after sunset after high-altitude winds blow them around.

"You need the right moisture, the right altitude and the right angle of light coming from the sun," he said. Too much sunlight hides the thin clouds, while too little fails to light them up well enough to see in darkness.

Understanding how natural night-shining clouds form, however, continues to elude researchers.

"The best knowledge we have suggests it's too dry for them to form, but they form anyway," said KSC atmospheric scientist Frank Nerceret. "We need to find out why that's happening, which is why we recently launched a new satellite."

That satellite, launched in April on NASA's Aeronomy of Ice in the Mesosphere (AIM) mission, will monitor the natural formation of the clouds near the polar regions of Earth to shed light on the mysteries of noctilucent cloud formation.

Endeavour's STS-118 astronaut crew is commanded by veteran astronaut Scott Kelly and includes NASA's first professional educator astronaut Barbara Morgan, who first joined the agency in 1985 as the backup for Teacher in Space Christa McAuliffe before the Challenger tragedy. The planned 11-to-14 day mission will deliver fresh cargo, spare parts and a new starboard-side truss segment to the International Space Station in Earth orbit.

Click here for SPACE.com's STS-118 launch and mission coverage.

• VIDEO: Shuttle Endeavour Launch Animation
• VIDEO: Teaching the Future: Teacher-Astronaut Barbara Morgan
• IMAGES: Barbara Morgan, Crewmates Train for STS-118