Astronauts on the shuttle Atlantis beamed live into Congress talks Thursday after winning praise from US President Barack Obama for helping to renew wonder in the mysteries of space.

The seven-strong crew, preparing to return to Earth Friday after a successful mission to repair the Hubble space telescope, addressed lawmakers live from space via a video-link from the shuttle.

"Thank you for the stunning and successful mission. You have opened a door on a new era of scientific discovery," said Senate science appropriations subcommittee chairwoman Barbara Mikulski.

"Hubble is the people's telescope and it wants to have another chance to educate a new generation of scientists and school children."

And a beaming Senator Bill Nelson, a former astronaut, told the crew: "I want you to know you have made the spring in the step of every American a little bit bouncier by what you have achieved."

Late Wednesday, the Atlantis astronauts also earned praise from Obama for extending the lifespan of the 19-year-old stargazer by at least five years, and help it peer further back into the origins of time and the universe.

"I'm hoping you guys recognize how important your mission is to the world as well as to this country," the president said in a phone call from the White House.

"I can assure you it's a high priority of mine to restore that sense of wonder that space can provide and to make sure we have a strong sense of mission, not just within NASA but for the country as a whole," Obama said.

The president spoke privately with the astronauts for six minutes, with an audio provided by the White House.

"What you guys represent is an example of what vision means in the space program, always describing our willingness to stretch beyond current boundaries and to look at things in new ways.

The shuttle astronauts will attempt to land back on Earth on Friday, touching down at NASA's Kennedy Space Center in Florida.

But with stormy weather a possibility, Mission Control instructed the astronauts to turn down some computers to conserve electricity in case Atlantis has to remain in orbit through the weekend.

Thunderstorms, rain, low clouds and gusty winds were forecast for Friday's two landing opportunities in Florida at 10:00 (1400 GMT) and 11:39 am (1539 GMT).

NASA had no plans to make Edwards Air Force Base, California, available as a backup landing site on Friday.

"The weather is iffy," Mission Control told Atlantis commander Scott Altman during a discussion of the landing strategy.

"As you know the weather can change rapidly in Florida. We do think there is a possibility we could land at Kennedy tomorrow."

Before beginning their return journey though, the crew shared their experiences with a Senate committee discussing funding for the US space agency, and were promised "a Hubble hug" on return by Mikulski.

"Hubble has struck a chord in human hearts around the world," said Grunsfeld.

"It's probably the most significant science instrument of all times. Astronomers use Hubble to try to answer the fundamental questions of where did we come from, where are we going and the history of the universe."

The committee was discussing NASA's 2010 budget released earlier this month by Obama and which ordered a review of NASA's Constellation project, due to replace the US shuttle fleet for manned space flight after next year.

The budget gave no further indication on the future of Constellation, NASA's ambitious project to return US astronauts to the moon and then take them on to Mars using its 1960s method of a rocket and reusable crew capsule.

The shuttle lifted off on May 11. It rendezvous-ed with Hubble two days later, using the shuttle's robot arm to haul the telescope into the cargo bay.

The observatory was released on Tuesday after five obstacle-filled spacewalks that added two new science instruments, a computer as well as gyroscopes and batteries to fortify the precision pointing and power systems.

The enhancements have equipped Hubble to search for the earliest galaxies, probe the mysteries of dark matter and dark energy as well as study planet-making processes.