CAPE CANAVERAL, Fla. -- Shuttle Discovery was converted into an orbital tugboat Friday, hauling the International Space Station to a higher altitude while crews on board the joined ships scrambled to pack up an Italian moving van.

Ceremony Today

A formal change-of command ceremony and a crew news conference are scheduled aboard the International Space Station at 1:12 p.m. EDT (1715 GMT) and 3:20 p.m. EDT (1920 GMT) Friday. Click here for live coverage.

Firing steering jets on the Discovery's tail, shuttle skipper Scott Horowitz and pilot Rick Sturckow boosted the 132-ton station up about two miles (3.2 kilometers).

The hour-long orbit-raising maneuver was the second series of thruster firings carried out by the Discovery crew to counteract the gravitational pull of the Earth, which gradually causes the altitude of the 17-story station to drop over time.

Eight other astronauts and cosmonauts, meanwhile, hustled to pack up an Italian shipping container now mounted to an Earth-facing port on the station's U.S. Unity module, which serves as a pressurized passageway to all parts of the outpost.

Considered one of the visiting shuttle crew's prime objectives, the so-called transfer operations must continue on schedule to clear the way for a spacewalk slated for Saturday.

That's because Discovery doesn't have enough fuel onboard to linger at the station beyond the end of its planned eight-day stay.

With the work largely proceeding as planned, mission managers gave a conditional go-ahead for the 6.5-hour spacewalk, which is slated to begin at 10:15 a.m. EDT (1415 GMT) Saturday.

"All this is based on a caveat -- that we do well on transfer," Canadian astronaut Steve MacLean told the joined shuttle-station crews from NASA's Mission Control Center in Houston.

Discovery astronauts Daniel Barry and Patrick Forrester aim to rig up power cables outside the station's $1.4 billion U.S. Destiny laboratory during the excursion, the second and final sortie planned during the shuttle's visit.

Moving a new crew into the station -- and an old crew out of the outpost -- are the top two priorities of NASA's 106th shuttle flight.

To that end, Discovery carried up a moving van filled with more than three tons of food, clothing and supplies for the third full-time crew of the station, which includes U.S. commander Frank Culbertson and Russian cosmonauts Vladimir Dezhurov and Mikhail Turin.

The cylindrical shipping container was attached to the Unity module Monday with the shuttle's 50-foot (15-meter) robot arm. It was unpacked by the end of the following day.

A ton of luggage, surplus gear and garbage now is being loaded aboard the so-called Leonardo module, which will be stowed back in the shuttle Sunday for a return trip to Earth.

Also on tap Friday: A formal change-of-command ceremony and a joint crew news conference.

Outgoing station skipper Yuri Usachev and two U.S. flight engineers -- Susan Helms and Jim Voss -- are slated to officially hand over command of the complex to Culbertson and his crew at 1:12 p.m. EDT (1715 GMT).

All 10 astronauts and cosmonauts aboard the linked shuttle-station complex then are scheduled to take part in a space-to-ground news conference at 3:20 EDT (1930 GMT).

In space since March, Usachev, Helms and Voss will depart the station next Monday aboard Discovery, heading off on a two-day trip back to Kennedy Space Center. Landing remains scheduled for 12:48 p.m. EDT (1648 GMT) next Wednesday.

Culbertson and his crew will remain in space until Dec. 9.