Two space walks are scheduled for Monday. With craft from Russia, Europe, and Japan at the International Space Station as well, Discovery's last mission may include a unique photo op.
Resupply activity aboard the International Space Station moves into full swing today as the combined crews from the space shuttle Discovery and the space station begin offloading cargo and preparing for the first of two space walks Monday.
The orbiter and its six-member crew arrived Saturday at 3:14 p.m. Easter Standard Time in what controllers called a "textbook docking."
Discovery's arrival marks the first time in the history of the space-station program that craft from each of the four major partners in the $100 billion project – Europe, Japan, Russia, and the US – are docked at the station at the same time.
Although Discovery and its crew reached the station on schedule, it would take another 40 minutes for the shuttle and station to grip each other firmly enough to allow the station crew members to welcome their newly-arrived colleagues.
As Discovery inched into its docking port at roughly half a mile an hour, the first step in the docking process – a so-called soft dock – took place as planned. At this stage, the two craft were mated but not yet firmly locked to one another.
But "it took a little bit longer than we could have liked for the hard mate to complete," said the mission's lead flight director, Bryan Lunney, referring to the second step that locks the craft together.
In essence, the shuttle's docking ring didn't sit squarely against the station side of the docking port, but had a tiny tilt to it. It took 40 minutes for the orientation of the station and shuttle to change with respect to Earth to give gravity a chance to counteract the tilt and bring the two halves of the docking system squarely together for the hard capture.