While the space shuttle Discovery's astronauts took time off on Thursday to enjoy the ride, colleagues on Earth prepared to begin the most complex part of the construction of the international space station.
The assembly of the $100 billion orbital outpost has been on hold since the 2003 Columbia disaster, but the success so far of Discovery's 13-day mission has cleared the way for NASA to resume construction flights as early as next month.
"We're about to really crank up the assembly of the space station once again," astronaut Michael Lopez-Alegria, commander of the next long-term space station crew, told reporters covering the shuttle flight from Houston.
Lopez-Alegria and Russian cosmonaut Mikhail Tyurin, who are due to launch aboard a Russian Soyuz rocket in September, will spend part of their stay aboard the station with Germany's Thomas Reiter, who arrived on July 6 on Discovery.
While Reiter stays behind, the rest of the seven Discovery astronauts are scheduled to leave the station on Saturday and return to Earth on Monday at the Kennedy Space Center in Florida.
The primary goal of the current shuttle mission was to test NASA's redesign of the shuttle's external fuel tank. Columbia broke up as it tried to land in 2003 because insulation foam from the tank had fallen off during liftoff 16 days earlier and damaged the heat shield on a wing.
The space agency had hoped to resume construction missions to the space station last year, but the first shuttle flight after Columbia revealed the problem with falling insulation foam had not been resolved. During Discovery's launch this July 4, however, only small pieces of foam that posed no threat to the shuttle popped off, and if everything continues to go well, NASA hopes to resume normal shuttle flights.
NASA needs to finish building the station before the aging shuttle fleet is retired in 2010.
The most complex work is slated to begin with the launch of the shuttle Atlantis and six astronauts as early as Aug. 28. The shuttle will carry the next piece of the station's metal truss as well as a new set of solar arrays.
Discovery's crew also paved the way for a resumption in construction by repairing the station's rail cart, which runs on the outside of the space station and is needed to haul components into position for installation.
NASA has pared the number of shuttle missions needed to complete the station to 16, relying on the resident station crews to pick up much of the work.
Lopez-Alegria and NASA astronaut Sunita Williams, who will arrive with the next Discovery crew in December, will make three spacewalks in nine days during their six-month stay in space. "It's a really critical time in the building of the space station," Williams said during Thursday's news conference.
The Soyuz capsule launching in September will also carry a space tourist to the station, Japanese entrepreneur Daisuke Enomoto. He is paying the Russians about $20 million for the trip and a 10-day stay.