The Discovery docked early Thursday at the station, also known as the ISS, where it is scheduled for an eight-day stay. The landing follows news Wednesday that NASA will temporarily ground future flights of its aging shuttles, after learning that a large chunk of insulating foam broke off Discovery's external fuel tank during. Still, the mission will remain on its 12-day schedule.
While at the ISS, the seven-member crew of Discovery will deliver a cargo container filled with supplies, perform three spacewalks and conduct routine maintenance on the station's equipment. It will also install a new control-moment gyroscope--one of four used by the ISS to maintain stability in orbit.
A top priority will be to continue inspections of the shuttle.
In the 54 months since the ISS opened, the crew has performed many experiments and studies on sciences and technologies that could be used in the next generation of space exploration, including long-term missions to the moon and Mars. Since 2003, when the shuttle Columbia disintegrated on it way back to Earth, the space station's work has been muted. NASA removed one of its three-member crews to save on resources, and the mission's completion date was pushed from 2006 to 2010.
NASA's mission with the ISS is, of course, inextricably tied to the success of the shuttle flights.
"The ISS is a testing ground for new technologies that would be used in long-duration space flight," said NASA spokesman Jim Rostohar. But he added that without the space shuttles, further exploration is stifled because, for example, it can't lift large pieces of equipment further in outer space. "When we had the Columbia accident, it put on hold the next phase of development."
Still, the space station is conducting invaluable research.
Much of its research is centered on living in space for long periods of time. For example, the ISS has conducted studies on mitigating bone loss that has occurred in the gravity-free zone of space flights. The concern is that lengthy space travel could produce the symptoms of osteoporosis and hamper humans' ability to return to Earth. Researchers have discovered that by having the crew exercise three times a day on spacecraft treadmills and with simulated weightlifting, bone loss is temporary.
Similarly, the ISS has studied effects on the brain as astronauts travel through the solar system and become acclimated to a sense of constant spinning. In the so-called Coriolis experiment, researchers showed that the spinning effect is a trick of the mind and that after 10 to 20 object-oriented exercises, the brain readjusts.
Scientists are also performing tests on new materials to shield astronauts from radiation, which would be useful if NASA uses nuclear-powered space craft for exploration. NASA's Office of Biology and Physical Research is currently developing materials to block radiation in space.
The ISS, a cooperative venture backed by Brazil, Canada, Japan, Russia, the United States and 11 nations of the European Space Agency, is the successor to NASA's Space Station Freedom project, which failed in 1993 after spending $11 billion with little progress. The ISS has reportedly cost more than $30 billion.
As of now, the ISS has a scheduled completion date of 2010, but because it's an international project and has a modular setup, the date could be extended because of the varying interests of different countries. Its original completion date was 2006, but that was delayed following the Columbia disaster. There are currently no plans for the ISS after 2010, according to a NASA representative.
The early stages of Discovery's flight appeared to go smoothly. Yet one day later, the crew discovered during the course of several safety tests developed after the 2003 disaster that a large piece of foam had shed from the shuttle during its ascent. The explosion did not damage the orbital, but debris chipped tiles on its exterior.
"Until we've fixed this, we're not ready to fly again," Bill Parsons, NASA's shuttle program manager, said during a press conference.
The grounding will affect the scheduled launch of the shuttle Atlantis in September.
Reuters contributed to this report.