Engineers at Mission Control in Houston, Texas, played some wake-up music for the seven shuttle astronauts at 0938 GMT, then greeted them with a hearty "Good morning Atlantis."

A brief silence followed, then shuttle commander Rick Sturckow answered: "Good morning Houston."

Sturckow also wished a good morning to all US marines "serving in Iraq and in Afghanistan and all over the world ... through all this great planet that we sail on the space shuttle Atlantis."

The shuttle missed two windows of opportunity to return to Earth on Thursday when thunderstorms blocked it from landing at the Kennedy Space Center in Cape Canaveral, Florida.

On Friday Atlantis has two chances to return to its Florida home -- at 1818 GMT and 1955 GMT -- before switching to target the alternative landing spot in California.

"If Florida weather does not cooperate, three opportunities are available at Edwards" at 1949 GMT, 2123 GMT and 2259 GMT, said the National Aeronautics and Space Administration.

Just before re-entry Sturckow and pilot Lee Archambault must fire thrusters to slow down the orbiter, which reaches speeds of more than 26,000 kilometers (16,000 miles) per hour.

After breaking out of orbit with a blast known as a "deorbit burn," the shuttle plummets earthward 20 times faster than a commercial airliner. But unlike a jet, the pilot gets only one try, due to lack of power.

The weather forecast remained unfavorable in Florida Friday. While conditions were better in California, they was expected to deteriorate later in the day with strong lateral winds.

NASA is sensitive about landing the shuttle in bad weather. Clouds below 2,400 meters (7,800 feet) block the pilot's vision as the shuttle aims for the landing strip.

NASA wants to land Atlantis by Saturday as the shuttle's hydrogen batteries providing its electric power would have just one more day of life.

It prefers to land the shuttle in Florida as it costs nearly two million dollars to return it from California piggy-backed atop a Boeing 747 and this would affect the schedule of future missions.

NASA plans to launch at least 12 more shuttle missions, including three this year, as it races to finish building the 100-billion-dollar ISS by 2010, when the space agency retires its three remaining orbiters.

It considers the station a vital part of US ambitions to send a manned mission to Mars.

While docked at the ISS during the current 13-day mission, astronauts successfully installed a new truss segment, expanding the station's laboratory with a new set of power-generating solar arrays.

The astronauts ventured out on four spacewalks to set up the truss and fix a thermal blanket which was damaged when the shuttle shot into orbit.

The small hole in the heat shield prompted concerns for the craft's safety on re-entry, but NASA declared it fit to return after the repairs.

Engineers stressed it posed no threat to the crew, unlike the broken tile that caused shuttle Columbia to break up on re-entry in February 2003, killing all seven astronauts on board.

Atlantis brings back with it Sunita Williams, who had been on the ISS since December. It left behind one crew member, Clayton Anderson, who is to stay on the orbiting research lab for four months alongside two Russian cosmonauts.

earlier related report
The STS-117 crew is getting an extra day in space thanks to poor weather conditions at Kennedy Space Center, Fla. Space shuttle Atlantis has five landing opportunities available Friday, with the first at 2:18 p.m. EDT in Florida. Thunderstorms in the vicinity of Kennedy forced flight controllers to wave off both opportunities Thursday. Controllers and the Spaceflight Meteorology Group will closely monitor forecasts for Friday's opportunities in Florida and at Edwards Air Force Base in California.

The first opportunity Friday is on Orbit 218 and calls for a deorbit burn at 1:16 p.m. The second is on Orbit 219, with the deorbit burn at 2:52 p.m. and landing at 3:54 p.m. at Kennedy.

If Florida weather does not cooperate, three opportunities are available at Edwards. The first is on Orbit 219. Thursday afternoon, the crew adjusted Atlantis' orbit to set the stage for this opportunity, which has the deorbit burn occurring at 2:46 p.m. and landing at 3:49 p.m.

The second opportunity for the California base is on Orbit 220. The deorbit burn would occur at 4:21 p.m. and landing at 5:24 p.m. The final opportunity is one orbit later which calls for the deorbit burn to occur at 5:58 p.m. and landing at 6:59 p.m. Friday's weather forecast for Kennedy calls for the threat of thunderstorms in the area and high winds are a possibility at Edwards. Opportunities are also available Saturday.

Atlantis launched June 8 and arrived at the International Space Station on June 10. While at the orbital outpost, the crew installed the Starboard 3 and 4 truss segment and conducted four spacewalks to activate it. During the third spacewalk, the crew repaired an out of position thermal blanket on the left orbital maneuvering system pod.

Atlantis also delivered a new station crew member, Flight Engineer Clayton Anderson. He replaced astronaut Suni Williams, who is the new record holder for a long-duration single spaceflight for a woman. She arrived at the station in December with STS-116. STS-117 is the 118th shuttle mission and 21st mission to visit the space station. The next mission, STS-118, is slated to launch in August.

Related Links
STS-117 Mission
Shuttle at NASA
Watch NASA TV via Space.TV
Space Shuttle News at Space-Travel.Com

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