Weather Clouds Saturday's Shuttle Launch

A turkey vulture appears to hide from the camera at a site near the NASA News Center at Kennedy Space Center. A wide-ranging bird, it is seen throughout Florida and the Space Coast. It is a common site around KSC. CREDIT: NASA/Ken Thornsley.

CAPE CANAVERAL, Fla. - NASA's space shuttle Discovery stands poised for its planned July 1 launch, though weather concerns cloud the upcoming space shot.

There is a 60 percent chance that afternoon storms, thick clouds and lightning may prevent Discovery from launching its seven-astronaut STS-121 crew toward the International Space Station (ISS), shuttle weather officials said Wednesday.

"Obviously these forecasts, while they sound a little bit gloomy, we've certainly launched with higher predictions of no-go," NASA test director Jeff Spaulding told reporters here at Kennedy Space Center (KSC). "As always, we'll evaluate the weather real-time and make the decisions on day of launch."

The poor weather outlook stretches through the first few days of Discovery's launch window, which closes on July 19, though launch officials are hopefully they will be able to secure at least four launch attempts over the first five days. If NASA can launch the spacecraft within the first three days, its 12-day mission could be extended one day to allow a third spacewalk to test heat shield repair techniques, launch officials.

Discovery's STS-121 mission, commanded by veteran shuttle astronaut Steven Lindsey, is the second orbiter test flight since the 2003 Columbia accident. The mission will test shuttle fuel tank modifications, orbiter inspection and repair methods, and deliver vital supplies to the ISS.

The countdown for Discovery's planned STS-121 launch, set for 3:48:37 p.m. EDT (1948:37 GMT)

Radar for the birds

Meanwhile launch officials have drawn new plans to scan for birds flying over Discovery's launch pad during Saturday's countdown, and could hold the liftoff if a pesky avian could be hit by the spacecraft during liftoff.

A new radar will monitor bird movements over Discovery's flight path and the spacecraft's launch countdown can now be held at T-31 seconds if there's a chance a vulture could be hit during liftoff.

The move, Spaulding said, is a result of Discovery's July 2005 launch, in which a vulture - a common bird seen around KSC's wildlife refuge location - was struck by the spacecraft's external tank during liftoff. It was the first time a bird has been struck by the vehicle during launch, he added.

"We wanted to make sure we could address the situation," Spaulding said, adding that launch officials want to prevent a bird strike that could damage Discovery's heat shield during liftoff. "It sounds like we have a new bird problem, but...we really don't have anything more than we've had previously."

Balloons are sometimes employed to scare off smaller birds, but a plan to frighten vultures and other large feathered flyers using an audio recording has stalled because speakers at Discovery's Pad 39B launch site point down - so pad workers can hear announcements - rather than skyward, Spaulding added.

Earlier KSC efforts to collect roadkill, a food source for vultures, has proven effective in reducing their numbers near Discovery's launch pad, and the birds will be trapped and released elsewhere on launch day, NASA officials said.

While pad workers continue to prepare Discovery for its July 1 launch, the spacecraft's payload is in ship shape, said Debbie Hahn, STS-121 payload manager.

The only remaining items to be packed aboard the orbiter - which includes a batch of fruit flies -will be installed in its middeck compartments at L-27 hours in the countdown, she added.

• Meet the STS-121 Crew: The Spacewalkers
• Meet the STS-121 Crew: The Flyers
• Return to Flight: NASA's Road to STS-121
• The Great Space Quiz: Space Shuttle Countdown