This story was updated at 9:54 a.m. EDT.
CAPECANAVERAL, Fla. -- NASA is hoping for a break in the weather in order to bringthe space shuttle Atlantis and its seven-astronaut crew back to Earth latertoday.
Rainshowers and low clouds near NASA?s Shuttle Landing Facility here at the KennedySpace Center (KSC) preventeda Thursday return for the shuttle and its STS-117 astronaut crew.
The orbiter is now slated to land at 2:18 p.m. EDT (1818 GMT) at KSC.
?We?regoing to be facing the same challenges at KSC,? NASA astronaut Tony Antonelli,serving as spacecraft communicator, told the Atlantis crew of today?s expected weatherconditions.
Missionmanagers are also calling up NASA?s backup shuttle landing site at Edwards AirForce Base in California in case the weather proves untenable in Florida, headded.
Commandedby veteran shuttle flyer Rick Sturckow, Atlantis? STS-117 crew is returninghome after a now 14-day mission to boost the power grid aboard the InternationalSpace Station (ISS).
The shuttleastronauts installed new starboardtrusses and solar arrays, furled an older solar wing and swapped out one ofthe station?s three-person Expedition 15 crew. The crew also repaireda torn thermal blanket on Atlantis? aft Orbital Maneuvering System (OMS)pod using surgical staples and medical staplers scavenged from shuttle and ISSmedical kits.
Returningto Earth with Sturckow are shuttle pilot Lee Archambault and missionspecialists Patrick Forrester, Steven Swanson, James Reilly II, Danny Olivasand Sunita Williams.
Williams isreturning to Earth after 194 days in space as part of the station?s Expedition14 and 15 crews. She has seta new world record for the longest duration spaceflight by a femaleastronaut and was replaced by fellow U.S. spaceflyer Clayton Anderson duringthe STS-117 mission.
Atlantiscarries enough supplies to stay in orbit until Sunday, though mission managershave set a Saturday deadline for any weather-related delays in order to keep aone-day margin in reserve in case of a technical glitch.
In all,there are two landing opportunities at KSC and three at Edwards, though somewindows overlap.
If rain andlow clouds again prevent Atlantis from landing at KSC on the first attempt, theshuttle could try to wait out the weather for an extra orbit and touch down inFlorida at about 3:55 p.m. EDT (1955 GMT).
?It will bea real-time call,? NASA spokesperson Allard Beutel said Thursday.
But if, inthat one orbit, the weather does not improve, the shuttle could instead press ontowards Edwards for a 3:49 p.m. EDT (1949 GMT) landing thanks to a brief engineburn late Thursday by the Atlantis crew. That maneuver, mission managers hope,could allow Atlantis to reach Edwards before the arrival of high winds duringtwo later California landing opportunities, which arise at 5:23 p.m. EDT (2323GMT) and 6:59 p.m. EDT (2259 GMT).
?Soundslike a nice game plan,? Sturckow told Mission Control Thursday after hearingtoday?s landing options.
NASAprefers to land shuttles at KSC, home to the orbiters? hangars and launch pads,because of the time and cost saved to once more prime them for flight.
Atlantis isslated for a second launch this year in December, when the shuttle is expected tohaul the European Space Agency?s Columbus laboratory to the ISS.
A landingat the Edwards site would cost an additional $1.7 million and add between sevento 10 days to ferry Atlantis back to KSC for refurbishment for its nextmission, NASA officials said Thursday.
?Obviously,we?d prefer to stay at the Cape if we can,? John Shannon, NASA?s deputy shuttleprogram manager, before Atlantis? first landing attempt.
Duringtheir mission, Atlantis astronauts also helped Expedition 15 crew resolve amajor Russiancomputer system shutdown last week that ultimately required an improvisedset of shunts, or jumper cables, to bypass surge-protector like circuits in sixvital control and navigation computers.
Expedition15 astronauts removed the jumper cables from some of the computers Thursday in additional troubleshootingefforts to see if they would still function properly, but they would not, NASA officials said.
NASA isbroadcasting the space shuttle Atlantis' STS-117 mission live on NASA TV. Click here for mission updates andSPACE.com's video feed.
- SPACE.com Video Interplayer: Space Station Power Up with STS-117
- IMAGES: Atlantis Shuttle?s STS-117 Launch Day
- Complete Shuttle Mission Coverage