But as they studied the path of the small debris from an old busted-up Soviet satellite, engineers ascertained it would remain at a safe distance.
A maneuver by the space station would have forced Discovery, which is delivering one last set of solar wings, to adjust its course for docking late Tuesday afternoon.
Mission Control radioed up the good news to both space crews early Monday evening.
"That makes things easier for (the station) and for us as well," Mission Control told the shuttle astronauts.
On Thursday, the three space station residents had to move into their emergency getaway capsule because another piece of space junk came uncomfortably close at 220 miles above Earth. In that case, there was short notice and the astronauts did not have enough time to steer out of the way.
LeRoy Cain, chairman of the mission management team, said the back-to-back debris threats were random.
Flight director Paul Dye also was not reading too much into the recent flurry of debris events. Besides last week's close call, a two-satellite wreck in a much higher orbit last month also spotlighted the growing problem of space junk.
"We seem to have a bit more than we've had in the past," Dye said Monday evening. "It's a little bit like traffic on the freeway. Sometimes it's bad and sometimes it's not, and sometimes you can figure out why and sometimes you're not sure where it came from."
To be safe, NASA never wants anything straying into an imaginary box around the space station that measures just over one mile by 15 miles by 15 miles. The 4-inch debris being tracked Monday was going to be "in the fringes of that," Dye said.
The odds of a hit have to be better than 1-in-100,000 to be of concern, Dye said. NASA has moved the space station to dodge debris eight times, most recently in August. Generally, engines on the Russian living quarters or the attached Russian supply ships are fired to alter the path of the entire station. It's a relatively easy job, but uses up precious fuel.
The debris this time was from a Soviet military satellite called Kosmos 1275, which broke up shortly after its 1981 launch. Russians believe a battery explosion did the satellite in, resulting in a cloud of 310 pieces of debris that slowly are falling into lower orbits.
Meanwhile, on board Discovery, the seven astronauts conducted an in-depth inspection of their ship's wings and nose with a laser-tipped boom Monday afternoon. It's standard procedure the day after launch to check for any damage that may have occurred during liftoff.
Cain said it appears, at least initially, as though Discovery made it through the launch "very, very clean."
A preliminary review of the launch video showed nothing of significance coming off Discovery's external fuel tank and striking the spaceship Sunday evening. Debris has been an overriding concern for NASA since a chunk of foam insulation broke off the external fuel tank and cracked open Columbia's wing in 2003. The shuttle broke apart during re-entry, and all seven astronauts were killed.
The shuttle flight has been reduced by one day and one spacewalk because of repeated delays in taking off. Three spacewalks are now planned.
Mission managers said the astronauts still should be able to complete most of their objectives during their 13 days in orbit. Besides installing the new solar wings, the crew will drop off a new urine processor for the space station's water-recycling system, as well as a new station resident, Japanese astronaut Koichi Wakata.
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