NASA managers said they might have the astronauts conduct more scans for damage later in the flight.
To close the distance, the astronauts conduct periodic firings of the shuttle's on-board thrusters.
The astronaut could use it inside the cabin and conduct EVA as well.
During the mission, astronauts will conduct research on materials and life sciences in the laboratory, which quadruples the space available in a shuttle for experiments.
American astronauts generally conduct spacewalks within the open bay of the Space Shuttle.
NASA hopes to begin building the station in the mid-1990's as an orbiting outpost where astronauts can conduct science experiments.
The astronauts conducted tests and photographed environmentally damaged parts of the Earth on their third day in space.
When American astronauts conduct space walks, they generally do so within the open bay of the space shuttle.
Working around the clock in two shifts, the astronauts will conduct 82 experiments involving more than 200 scientists from 13 countries.
The Soviet press said the astronauts would also start checking equipment on Mir and conduct medical and scientific experiments.