Even as bad weather in Florida threatened their scheduled return to Earth, the astronauts aboard space shuttle Atlantis took time Thursday to answer questions from senators, schoolchildren and reporters.

"Does it feel different to go from the Earth's atmosphere to outer space?" Malary Voucher, who had been at the National Air and Space Museum when approached by a FOX camera crew Wednesday, asked via videotape.

"What was it like floating in the space shuttle and outside the space shuttle?" wondered Lane Goddard, also at the Air and Space Museum.

"When you look down and see the Earth, what thoughts go through your mind?" asked Doug in Missouri, who sent in his question via Twitter.

Sen. Barbara Mikulski, D-Md., chairwoman of the science appropriations subcommittee, was more effusive when she spoke with astronauts via videolink earlier Thursday.

"When we talk about the Hubble and giving it essentially a new life and a new way of going and seeing the universe, you've touched our hearts and you've also made history," said Mikulski.

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The astronauts checked their ship's flight systems and monitored the weather at Kennedy Space Center at Cape Canaveral, which was being pounded by fierce thunderstorms. More bad weather was expected Friday morning when Atlantis was due to land at 10 a.m.

Still, the storms couldn't dampen the astronauts' spirits, which were high after having successfully upgraded and repaired the Hubble Space Telescope.

Fresh off a call from President Barack Obama the day before, the seven astronauts told Mikulski and Sen. Bill Nelson, D-Fla., their most nail-biting moments of the past 1 1/2 weeks.

"You should have seen the action out the back window," said pilot Gregory Johnson. "I was on the edge of my seat."

With all their work completed in orbit, the astronauts aimed for a Friday morning touchdown at Kennedy Space Center, but given the dismal weather reports, they were conserving power in order to remain aloft until Monday, if necessary.

Mission Control warned that Friday's weather would be "iffy." The backup landing site in Southern California could be used Saturday, if Florida keeps getting hit by storms.

"We flew over today, saw it looked kind of nasty at the moment, but saw some clearing behind it — maybe," commander Scott Altman radioed down. "As long as you think there's a chance, we'll be willing to do whatever it takes."

Atlantis rocketed away on NASA's last visit to Hubble on May 11. In five back-to-back spacewalks beset by stuck bolts and other problems, the astronauts installed two top-of-the-line science instruments and replaced burned-out electronics in two other science scopes.

They also gave the 19-year-old observatory a new computer for sending back science data, freshened up the power and pointing systems, and beefed up the exterior with steel foil sheets.

When it came time to let Hubble go Tuesday, chief repairman John Grunsfeld recalled turning to Altman and saying, "You know, we really did it."

The refurbished Hubble is expected to perform better than ever over the next five to 10 years and probe even deeper into the universe, as far back in time as 500 million to 600 million years from creation.

Besides watching the weather, NASA had been keeping shuttle Endeavour ready for liftoff in case a rescue mission were needed. On Thursday morning they canceled the backup plan, put in place long ago to minimize the risk the Hubble repair crew was taking.

With the astronauts having only enough air to last until Monday, the rescue ship, Endeavour, at this point could not be launched in time to save them.

The six men and one woman had to launch into a 350-mile-high orbit to get to Hubble and had nowhere to go in the event their ship was damaged seriously by liftoff debris or space junk, a bigger problem than usual so high up. The international space station is in a different orbit and unreachable.

NASA considered this last Hubble mission so dangerous that it was canceled in 2004, a year after the Columbia tragedy. It was reinstated in 2006.

On Wednesday, NASA said an extensive survey of Atlantis' vulnerable wings and nose showed no evidence of worrisome trouble, and managers cleared the shuttle for re-entry.

A hole the size of a dinner plate in the left wing, brought down Columbia.

The Associated Press contributed to this report.