This story was updated at 9:17 a.m. EDT.

CAPE CANAVERAL, Fla. - Bad weather thwarted the planned landing of the shuttle Atlantis for the second time in as many days Saturday, keeping its seven-astronaut crew in space for yet another extra day.

Atlantis was slated to land on a runway here at NASA?s Kennedy Space Center (KSC) at 9:16 a.m. EDT (1316 GMT) to end a 12-day trek to fix up the Hubble Space Telescope. But persistent thunderstorms prevented the shuttle?s return just as they did on Friday. The astronauts will try again on Sunday to conclude a now 13-day mission.

?The weather at KSC has not cooperated with us today,? Mission Control radioed the Atlantis crew. ?We are waving off for the day.?

Led by veteran commander Scott Altman, the shuttle?s seven-astronaut crew had already circled the Earth for awhile to wait out the weather until their second landing attempt also slipped away.

?There was just no hope that it was going to get any better,? said John Madura, head of the spaceport?s weather office.

The next chance to land Atlantis in Florida comes Sunday morning at 10:11 a.m. EDT (1411 GMT), with a second chance at 11:40 a.m. EDT (1540 GMT) on a backup runway at the Edwards Air Force Base in Southern California. Atlantis has enough supplies to stay in space through Monday before its oxygen supplies run out, mission managers have said.

Madura told SPACE.com that the weather forecast for Florida Sunday remains bleak. Severe thunderstorms from a low pressure front have battered the spaceport and surrounding area for days, though conditions will improve slightly tomorrow. Good landing conditions are expected in California through Monday.

But any chance to land in Florida is a welcome one for NASA, Madura said. The agency prefers to land shuttles at their home port here because it saves about a week of time and the $1.8 million required for transporting orbiters back from California atop a modified jumbo jet carrier.

NASA?s flight rules forbid attempting to land a space shuttle on a runway shrouded by low clouds or with rain storms within 30 miles (48 km). Space shuttles cannot fly through rain because the moisture can damage the thousands of protective heat shield tiles lining their bellies.

Returning home aboard Atlantis with Altman will be shuttle pilot Greg H. Johnson and mission specialists Michael Good, Megan McArthur, John Grunsfeld, Michael Massimino and Andrew Feustel.

During five back-to-back spacewalks, Atlantis astronauts installed new instruments, replaced old parts and repaired Hubble?s long-dead main camera and spectrograph - two instruments that were never designed to be fixed in space. The space telescope is now more powerful than at any time since its 1990 launch, mission managers said.

Hubble scientists said the astronauts? repairs and upgrades to the 19-year-old space telescope have extended its life through at least 2014, if not longer. Spacewalking astronauts also attached a docking ring to Hubble that will allow a robotic spacecraft to grab onto the space telescope sometime after 2020, when its mission ends, and send it plunging into the Pacific Ocean.

The mission is NASA?s fifth and final flight to Hubble before the agency retires its shuttle fleet in 2010. The replacement, NASA?s Orion crew capsule, will be used to ferry astronaut to the International Space Station and, ultimately, back to the moon.

NASA initially canceled the mission because of its risk a year after the 2003 Columbia disaster, but reinstated in 2006 after successfully resuming shuttle flights and testing heat shield repair and inspection techniques.  A second shuttle - Endeavour - was readied as a rescue ship in case Atlantis suffered serious damage during the flight. No rescue was required, and the astronauts successfully repaired Hubble.

In all, their mission cost about $1.1 billion, a fraction of the $10 billion invested in Hubble since its inception and launch.  

SPACE.com is providing continuous coverage of NASA's last mission to the Hubble Space Telescope with senior editor Tariq Malik in Cape Canaveral, Fla., and reporter Clara Moskowitz in New York. Click here for landing coverage, mission updates and SPACE.com's live NASA TV video feed.

  • New Video - Home Movies From Hubble - Telescope?s Release
  • New Video Show - Hubble's Final Shuttle Service Call
  • Image Gallery - Hubble?s Latest Views of the Universe: Part 1, Part 2