By Irene Klotz
CAPE CANAVERAL, Fla., March 8 (Reuters) - Countdown clocks at the Kennedy Space Center in Florida began ticking on Saturday toward Tuesday's launch of space shuttle Endeavour carrying a Japanese lab section and Canadian-built robot for the International Space Station.
Liftoff is targeted for 2:28 a.m. EDT/0628 GMT. Meteorologists predicted clear skies and light breezes, with a 90 percent chance conditions would be suitable for liftoff.
The seven-man Endeavour crew arrived at the Florida spaceport early on Saturday, delayed several hours by a cold front pushing through central Florida that whipped up winds, thunderstorms and sporadic heavy rain.
"We've had some interesting weather over the last 24 hours," shuttle weather officer Todd McNamara told reporters on Saturday.
The crew includes two veteran NASA astronauts: commander Dominic Gorie and lead spacewalker Richard Linnehan; rookies Greg Johnson, Michael Foreman, Robert Behnken and Garrett Reisman; and Japan's Takao Doi, who flew on a shuttle research mission in 1997.
Reisman will replace France's Leopold Eyharts as a member of the space station crew.
"We all just wanted to convey how excited we are to be here for launch week," Gorie said after the crew's belated arrival. "We've got a very, very ambitious flight schedule, but with a great orbiter waiting for us and this great crew, we're going to have a great mission."
The shuttle is scheduled to spend 16 days in orbit, NASA's longest planned mission to the space station so far. With just 11 flights remaining to the orbital outpost, NASA wants to squeeze in as much construction and maintenance time as possible before the shuttles are retired in two years.
A 12th shuttle mission to upgrade and repair the Hubble Space Telescope is planned for later this year.
During their 12 days at the station, Endeavour's astronauts plan to conduct five spacewalks to install the first part of Japan's Kibo complex and set up a robot to help with station maintenance and other tasks. The main part of Kibo, which is Japanese for "hope," is due to arrive in May.
Japan has spent about $250 billon yen, or more than $2.4 billion, to develop Kibo, said Hiroki Furihata, deputy director of the Japanese Exploration Development Agency liaison office at Kennedy Space Center.
Also on Saturday, Europe, which recently began operating its space station laboratory Columbus, was preparing for the debut flight of its unmanned station cargo ship aboard a massive Ariane 5 rocket from Kourou in French Guiana. Liftoff was scheduled for 11:03 p.m. EST/0403 GMT on Sunday.
The vessel, known as the Automated Transfer Vehicle, or ATV, will idle in orbit during Endeavour's flight before closing in on the station for several rendezvous and navigation tests prior to berthing. Europe plans to fly one ATV a year for the next five years to help keep the station supplied with fuel, food and other gear.
The space station, which is about 60 percent complete, is a $100 billion project of 15 nations. Next year, the station's crew size is expected to double from three to six members.
Endeavour, which will be NASA's 122nd shuttle mission, is the second of six shuttle flights NASA plans for this year. (Editing by Eric Walsh)