Space station flight controllers have successfully tacked a pair of glitches that clears the way for a weekend shuttle visit to the orbital laboratory.

NASA’s space shuttle Discovery is poised to launch towards the International Space Station (ISS) at 9:35: 47 p.m. EST (0235:47 GMT) and dock at the outpost on Saturday. Commanded by veteran spaceflyer Mark Polansky, the shuttle’s STS-116 mission is aimed at delivering a small new section of the station, exchanging one of the outpost’s Expedition 14 crewmembers and rewiring the outpost’s power grid.

To prepare for Discovery’s arrival, ISS flight controllers plan to boost the station’s orbit at 4:36 p.m. EST (2136 GMT) today using engines aboard an unmanned Russian cargo ship currently moored at the orbital laboratory.

Today’s maneuver follows a brief, three-minute and 16-second engine firing Wednesday that was cut short automatically due to a slight shift on the space station’s orientation. Flight controllers believe the shift is normal, and traced it back to the addition of a 17.5-ton pair of portside trusses and new solar arrays in a September shuttle flight.

The Progress 23 craft will fire its engines for about 23 minutes today. If the burn does not go as planned, it could cut into Discovery’s launch window (which currently closes on Dec. 17) since the shuttle would have to liftoff on odd days (Dec. 7,9,11,13) until Dec. 15, then daily through the 17th, to ensure Discovery’s STS-116 crew dock at the ISS on Flight Day 3. Additional launch days are possible should shuttle mission managers approve the spacecraft for flight during the year-end change from 2006 to 2007.

Meanwhile, engineers have also reset an open circuit breaker that regulates power to one of two motors that allows the space station’s portside Solar Alpha Rotary Joint to rotate its outboard solar arrays to track the Sun. The circuit breaker popped open during a software test last week.