With rainy weather possible in Florida on Friday, the Atlantis astronauts were asked to power down less-critical equipment Wednesday to conserve hydrogen and oxygen for the shuttle's fuel cell system in case landing is delayed. Touchdown currently is planned for 10:01 a.m. Friday, but additional opportunities on both coasts are available Saturday and Sunday.

Commander Scott Altman. Credit: NASA

With the power downs, "that puts us about 21 hours above an 11 (days) plus two (extension days), which gives us a lot of margin down the road as we keep an eye on the weather," astronaut Dan Burbank radiod the crew. "Certainly, we're all hoping for the best here and that we'll get you home on Friday. That's still our hope."

The Spaceflight Meteorology Group at the Johnson Space Center in Houston is predicting scattered clouds at 4,000 feet at landing time Friday, a broken deck at 10,000 feet, a chance of broken clouds at 4,000 feet and a chance of thundershowers within 30 nautical miles of the shuttle runway.

NASA's Mission Management Team, meanwhile, is wrapping up analysis of a heat shield inspection carried out by the crew Tuesday. While the assessment was not yet officially complete, Burbank told commander Scott Altman there were no signs of trouble.

"We have one bit of good news," he reported. "All the imagery from the late inspection has been reviewed. Now, we still have to finish out the final reviews on it, but there are zero areas of interest."

"OK, copy, Houston, thanks. Zero areas of interest," Altman said.

During a traditional on-orbit crew news conference earlier Wednesday, Altman said he was confident Atlantis would be cleared for entry as is.

"We did a pretty complete survey yesterday," he told CBS News. "I was very happy with all the imagery and the activity that we had to make sure we got as good an inspection as possible. We used the sun to help us inspect both the wings to make sure we had better pictures of the leading edge of our wings for re-entry.

"So I feel very confident we have all the data that we need, I'm letting the experts crunch that (data) to make sure everything looks good. From our vantage point, we think it's probably looking very good for entry and we're looking forward to that."

LeRoy Cain, chairman of the MMT and deputy shuttle program manager at the Johnson Space Center, planned to brief reporters later today on the status of the on-going heat shield assessment and NASA's strategy for keeping the shuttle Endeavour on stand by for a possible rescue mission if any major problems are discovered between now and re-entry.

Endeavour has been poised atop pad 39B at the Kennedy Space Center, ready since Monday for the start of a three-day countdown to launch if needed. Early today, engineers protectively started a rescue mission countdown to preserve the option of launching Endeavour as soon as possible if problems develop.

Mission managers originally planned to release Endeavour from rescue stand-by duty after the final heat shield inspection, but they have decided to continue Endeavour's processing until Atlantis successfully fires its braking rockets to drop out of orbit. Given the prospects for bad weather Friday, that could happen as late as Saturday or Sunday, in a worst-case scenario, leaving NASA little time to launch Endeavour. Hence the decision to start conserving power.

Assuming the MMT clears Atlantis' heat shield for entry, an extended "hold" will be inserted in Endeavour's countdown before fuel cell loading early Thursday. No one expects a rescue mission to be needed, but NASA is keeping all options open until Atlantis successfully begins the trip home.

The Atlantis astronauts successfully overhauled and upgraded the Hubble Space Telescope during five back-to-back spacewalks, installing two new instruments, repairing two others, replacing six gyroscopes, six batteries, a star sensor and a science data computer. They also attached three new insulation panels to improve temperature control.

The telescope was released back into open space early Tuesday and the astronauts took the day off Wednesday to relax and enjoy the view from 350 miles up. Shortly after noon, flight controllers arranged for the shuttle astronauts to chat with the three-man crew of the International Space Station.

"Hello Atlantis, this is International Space Station, we're very glad to welcome you guys," station commander Gennady Padalka called from 220 miles above Europe.

"Hey, and greetings to you all," Altman replied as the shuttle sailed high above the central Atlantic Ocean.

"It's very wonderful to talk to you guys," called Japanese astronaut Koichi Wakata. "Congratulations on the wonderful (Hubble servicing) EVAs. You guys did an outstanding job."

Station flight engineer Michael Barrett said the lab crew had followed the exploits of the Hubble mission and "it's just the greatest thing to see these two remarkable machines made by such remarkable people coming together again, this time for the last time."

"We wanted to offer some heartfelt congratulations for a job well done," he said. "We also know how hard you guys have been training and how personally invested in this great telescope you've all been. I guess we all kind of envy you the chance to touch Hubble one final time and get her all commissioned for another several years of discovery. Again, we just think you guys have done an awesome job. It's great to hear laughter in the background, we know how intensively you've been working."

"Thanks, Mike, we've had a great time up here," shuttle robot arm operator Megan McArthur said. "It's really fun to be sharing space with you."

Late this afternoon, sources said, Altman and his crewmates may take a private phone call from President Obama.

Asked during their news conference what the crew would advise the president about NASA's future, Altman joked he would suggest making lead Hubble spacewalker John Grunsfeld the next NASA administrator.

Answering the question, Grunsfeld said he would tell the president that the "core mission of NASA is actually a pretty good one."

"When President Obama is briefed by the new (yet-to-be-named) administrator on all the things that NASA does, I think he'll be incredibly impressed by the breadth of things that we do in climate work, Earth observation, aeronautics, space science, all those things that have been our core strengths.

"And in human spaceflight, as much as we love low-Earth orbit, it's time to leave low-Earth orbit, go out and explore the cosmos. ... We have lots of places near by, near-Earth objects, the moon, Mars, it's a great solar system and it's time for humans to start moving out. And that's what we're (planning). What we have to do is get down to the business of actually doing it. And I think that's what I would say to President Obama."

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VIDEO: SUNDAY NIGHT UPDATE FROM HST CONTROL CENTER PLAY
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