The repairs made to the space shuttle Discovery while it was in orbit are the first step toward other missions in the solar system, a returning astronaut said Tuesday.

• INDEPTH: Space

Discovery lands in California Tuesday. (Courtesy: NASA TV)

Discovery's landing completes the first shuttle mission since Columbia's seven astronauts were killed during re-entry in February 2003.

Lightning and rain near the Kennedy Space Center in Florida forced Discovery's crew to land at Edwards Air Force Base in California.

The 14-day mission included an unprecedented spacewalk to remove two pieces of dangling tiles on the shuttle's heat shield while it was docked at the International Space Station.

Astronaut Steve Robinson was held in place by the station's Canadarm2 robotic arm as he pulled out the pieces, which NASA feared might cause heating problems during re-entry.

As people prepare to explore the moon and Mars, astronauts will need to learn how to make such repairs in orbit, Robinson noted.

"The first step is to show we could get access, and access is everything," Robinson told a post-flight news conference.

The crew's two major accomplishments were to get the shuttle flying again and to deliver supplies to build the International Space Station, said Commander Eileen Collins.

Collins said she thought of Columbia's crew every day. "They believed in the space mission, and I know if they're listening to me right now, they would most certainly want us to continue."

Canadian technology indispensable

The crew accomplished all of their objectives, but Discovery shed insulating foam from its external fuel tank during liftoff – the same problem that doomed Columbia. This time, the foam didn't affect the shuttle's safe return.

Shuttle being serviced at Edwards Air Force Base in California, Tuesday.

NASA officials have suspended shuttle flights until they understand the foam problem and fix it. They haven't said when the shuttles will resume flying.

"We're going to try as hard as we can to get back in space this year, because we have a big construction project we're working on, and we need the shuttle to do it," NASA Administrator Michael Griffin said. "But we're not going to go until we're ready to go."

Bill Readdy, NASA spaceflight chief, praised the Canadian contributions to the mission: robotic arms on the shuttle and station, and an orbiter boom sensor tipped with laser cameras that inspected for damage while the shuttle was in orbit.

"My compliments to your fellow countrymen up there in Canada for the work that they have done," said Readdy. "They've been with us all along in the return to flight effort and I think they have done a magnificent job."

The astronauts will be reunited with their families in Houston on Wednesday. The shuttle will fly back to its base in Florida on a modified jet at an estimated cost of $1 million US.