CAPE CANAVERAL, Fla. - Shuttle Endeavour's orbital cartographers took off on the first piloted space voyage of the new century Friday, setting sail on a $600 million mission to make a 3-D map of planet Earth.

With six astronauts from the U.S., Europe, and Japan strapped into its crew cabin, Endeavour thundered off its Kennedy Space Center launch pad at 12:43 p.m., blazing a brilliant path through clear skies as it rumbled toward orbit.

"Looks like a great day to go fly a great opportunity to send you on your earth-mapping mission," NASA Launch Director Dave King told the crew minutes before Endeavour vaulted off into space.

"The whole crew is ready," shuttle skipper Kevin Kregel replied. "We appreciate all your hard work, and were ready to map the world."

Coming up next: circling 145 statute miles above the planet, the astronauts will attempt to raise a 20-story-tall radar antenna from a cargo-bay cannister that looks like an oversized oil drum.

If all goes well, the mast will be the longest fixed structure ever deployed in space. "It's a pretty impressive-looking piece of machinery," said NASA lead flight director Paul Dye. Added Endeavour mission specialist Gerhard Thiele, a German astronaut representing the European Space Agency: "The mast is an engineering masterpiece."

The raising of the 200-foot (60-meter) boom will come early this evening. The process is expected to take about 17 minutes, and time will be of the essence.

The astronauts must have the mast deployed and checked out by Saturday afternoon to complete their mapping mission. And if the mast jams, or fails to extent to its full reach, the crew could end up returning to Earth empty-handed.

"The mast has to be all the way out - and confirmed all the way out - to get the science that we desire," said Kregel.

"If the mast is not fully deployed...we won't be able to do the mission," Thiele added.

A back-up plan already is in hand. If the mast fails to deploy completely, mission specialists Thiele and Janet Kavandi will don bulky spacesuits early next week and float out into the shuttle's cargo bay in an emergency bid to raise the boom.

The spacewalking duo will be prepared to open the mast canister and crank the boom into place either with power tools or manually. Doing the job by hand with a simple ratchet wrench would be quite a chore.

"Well see the Earth as weve never seen it before, so it will be like rediscovering our own planet."

"That would take, gosh I can't even remember -- something like 30,000 turns [of the wrench]," Kavandi said. "It would take something like seven to eight hours to do it."

If the mast fails to retract at the end of the mission, the protruding boom would make it impossible for the astronauts to shut the shuttle's payload bay doors - a job crucial to a safe atmospheric reentry.

The 60-foot-long doors must be closed and latched tightly to protect the ship and its crew from the intense heat experienced during reentry -- temperatures that range up to 3,000 degrees Fahrenheit (1,650 degrees Celsius).

Kregel and copilot Dom Gorie in that case would back Endeavour away from the jettisoned boom to keep the shuttle and their crew mates out of harm's way.

"If we have any problems with the boom, whether it breaks or whether we can't retract it for whatever reason ... there are devices on board that we can jettison the whole canister and mast assembly. And we can do it in a very slow methodical method, and we could also do that very quickly," Kregel said. "Dom and I are both trained to do that at a moment's notice."

Despite the potential problems that can crop up, Kregel and his crew expected to mast deployment to come off without and hitch. And if that's the case, the astronauts will begin mapping operations as Endeavour races through space at 5 miles per second (8 kilometers per second).

At that point, the tedium begins.

Working in two shifts around the clock, the astronauts will spend nine days monitoring radar data recorders and swapping out some 270 tapes that will hold enough data to fill 13,500 compact disks.

"The nominal tasks that we have are to change the tapes and monitor the recorders. And monitoring is very demanding, but very repetitive and not very challenging," said Endeavour payload commander Janice Voss.

"It's like you driving a car down the highway, down a long straight road at the same speed for an hour. You don't dare fall asleep or doze off or spend too much time talking to your companion, or some dog is going to run across the road and you're going to be in the ditch. Or some drunk driver is going to swerve across the middle and your going to have a head-on collision," she said. "So the challenge is to stay alert all that time when the task that you're doing is not changing very much but requires constant attention."

The chores might be monotonous, but Voss said they are every bit as critical to mission success as the raising of the boom.

The shuttle's radar system will be mapping 259-mile (417-kilometer) swaths of Earth's surface each orbit and any crew slip-up could lead to gaps in an otherwise near-global map.

"Once you start mapping, if you make a mistake you have lost data," Voss said. "So in many ways, the hard part of the mission is after the mast comes out, because you have no flexibility left."

Dye and other flight directors are philosophical about the data that will be lost.

"You can look at it a lot of different ways. But I figure you can look at it as a glass that's 10 percent empty or 90 percent full," Dye said. "And I think a 90 percent full glass is a pretty good mission success criteria."

In any case, the mapping data gathered by Endeavour's crew promises to be a treasure trove for researchers in various fields of study. It is expected to be a scientifically accurate and artistically beautiful 3-D map of Earth that will be unrivaled in terms of coverage.

The most sophisticated radar system ever flown in space will map between 70 and 80 percent of the landmass of the planet - home to 95 percent of the world's 6 billion people - during the planned 11-day mission.

Strange as it might seem, scientists now have better topographical maps of Venus and Mars than they do of our own home planet. Consequently, researchers are anxious to get their hands on a near-global map that is 30 times as precise as any available today.

"We'll see the Earth as we've never seen it before, so it will be like rediscovering our own planet," said Diane Evans, chief scientist of NASA's Earth Science Program at the Jet Propulsion Laboratory in Pasadena, California.

Added Kregel: "In 11 days, we can [map] just about everything -- every land mass on the Earth -- between the two arctic circles. I think that's pretty incredible."

Endeavour and its crew are scheduled to cap the mission with a February 22 landing at KSC's 3-mile (4.8-kilometer) shuttle runway.