T minus three weeks for Atlantis crew in practice countdown

Less than three weeks before their targeted May 14 liftoff to the International Space Station, six astronauts are strapped in their seats inside Atlantis while countdown clocks tick at Kennedy Space Center.

The crew and launch teams are in the midst of a countdown dress rehearsal that will conclude four days of pre-launch training in Florida.

Mission commander Ken Ham, pilot Tony Antonelli and mission specialists Steve Bowen, Mike Good, Garrett Reisman and Piers Sellers this morning dressed in orange Advanced Crew Escape Suits, they bulky orange suits worn during the launch and entry phases of flight.

Around 7:45 a.m., they walked out of KSC's Operations and Checkout Building, where crew quarters are located, and boarded the silver "Astrovan" for a ride to pad 39A under armed escort.

Teams are following all the same steps they'll take on launch day.

Today, however, the countdown will stop at T minus four seconds, simulating a main engine shutdown around 11 a.m. Then the crew will climb out of the shuttle and follow emergency escape procedures leading them to the slide-wire baskets they would try to ride to the ground in the event of a fire.

The astronauts plan to return to Houston later today.

On Sunday, KSC crews plan to install the heavy cargo for the 12-day mission into Atlantis' payload bay.

The shuttle will haul a Russian module to the station and a platform of spare parts including solar array batteries and a communications antenna.

The missin's official launch date won't be set until early May. Atlantis' flight is one of three remaining shuttle missions.

IMAGE: At Kennedy Space Center this morning, the crew of space shuttle Atlantis' STS-132 mission, dressed in their orange launch-and-entry suits, were greeted by employees and media representatives on hand as they departed from crew quarters in the Operations and Checkout Building. In the left row, from front, are pilot Tony Antonelli followed by mission specialists Garrett Reisman and Steve Bowen, who is capturing the moment with his own camera. In the right row, from front, are commander Ken Ham followed by mission specialists Michael Good and Piers Sellers. Photo credit: NASA/Cory Huston.