Astronaut Randy Bresnik may be expecting his wife Rebecca to give birth, but that hasn't shaken his focus for a planned spacewalk outside the International Space Station today to install new video antennas and other equipment.

Bresnik and crewmate Mike Foreman plan to venture outside the station at 9:38 a.m. EST (1338 GMT) this morning and spend 6 hours upgrading the space station's systems. A massive cargo carrier laden with tons of spare parts will also be moved to the station from the linked shuttle Atlantis later today.

"Randy is 100 percent focused on this spacewalk," NASA's lead space station flight director Brian Smith told reporters late Friday.

Bresnik's daughter was expected to be born as early as Friday, but could come today or later, Smith said. Mission managers will work with Bresnik's flight surgeon to come up with a plan to notify the astronaut if his daughter is born during the spacewalk. Bresnik is only the second American to be in space while his wife is giving birth.

The uncertainty of the baby girl's arrival has not affected preparations for today's spacewalk, but more late-night false alarms on the station Friday – which erroneously indicated a potentially dangerous depressurization event for the second night in a row – have forced Mission Control to make some changes.

"There's going to be a 30-minute time hit and we are making adjustment for that," said space station flight director Jerry Jason in an early morning update. The spacewalk was initially slated to begin at about 8:18 a.m. EST (1318 GMT).

Mission Control also plans to let the astronauts sleep an extra half hour and will likely cut unnecessary get-ahead chores from today's spacewalk to compensate for lost time, Jason said.

The alarms sounded at about 10 p.m. EST (0300 Sat. GMT) while all 12 astronauts on the linked station and shuttle Atlantis were sleeping. Bresnik and Foreman were camping out in the station's Quest airlock, a process that allows them to sleep at a lower pressure than the station to purge their bodies of nitrogen in order to prevent developing the bends while working outside in their low-pressure NASA spacesuits.

Because of the alarms, the station automatically interrupted that pre-spacewalk campout and equalized the pressure between the airlock and space station. Ventilation fans shut off too, kicking up dust that set off a smoke alarm in the airlock, but all the astronauts were safe at all times.

The time required to reset the station's systems meant Bresnik and Foreman had to stop their campout. They will now have to spend time early Saturday exercising while wearing oxygen facemasks to purge their bodies of nitrogen ahead of the spacewalk. The exercise technique is a tried-and-true method for spacewalk preparation.

NASA engineers believe the false alarms, which also sounded late Thursday, are related to a new Russian module called Poisk, which arrived at the station earlier this month and serves as a research area, docking port and airlock.

Saturday's spacewalk will be the fifth orbital excursion for Foreman and the first for Bresnik.

The crew woke up today at 3:58 a.m. EST (0858 GMT), half an hour later than originally planned, to the song, "Voyage to Atlantis" by The Isley Brothers, which was played specially for mission specialist Bobby Satcher.

Atlantis astronauts are in the midst of an 11-day mission to deliver tons of huge spare parts to the space station – pieces so big, only NASA's shuttles can carry them. NASA wants to ship as many extra parts and gear to the station as possible before the planned 2010 retirement of its three remaining space shuttles.

Earlier this week, shuttle astronauts attached another massive shelf-like carrier - laden with spare pumps, tanks, a gyroscope and other gear – to the station. The shuttle is due to undock from the station next week, just before Thanksgiving, and land on Friday.