Work on International Space Station Continues

HOUSTON, Nov. 16 — Even as the shuttle Discovery touched down at the Kennedy Space Center last week, the shuttle Atlantis was being readied for a mission to take up another new module to the International Space Station as early as Dec. 6.

Whether the launching will happen on time depends largely on what the station’s commander, Peggy Whitson, the Russian cosmonaut Yuri Malenchenko and the American astronaut Daniel M. Tani get done in a nonstop series of tasks inside and outside the station.

“We’re in the midst of a very dynamic and exciting — but also very challenging — stage,” said Kenneth O. Todd, a manager of the space station program, in a briefing with reporters here on Friday.

The astronauts’ work began with a successful spacewalk on Nov. 9, and includes two more spacewalks, scheduled for Nov. 20 and 24. The pace will not let up, even on Thanksgiving, as the astronauts perform a series of moves to prepare the station for the arrival of Atlantis and the European-made Columbus module.

The series of on-orbit tasks is so complex that Rob Navias, a mission commentator, has called it a “modular shell game.”

So far, the astronauts have removed the shuttle docking port from the current position at the end of the Destiny module and placed it on the end of the new Harmony module, which had been put in a temporary position as part of the last shuttle mission. Harmony was then moved to the end of the Destiny module, and now can serve as the docking station and a connection point for Columbus and a Japanese laboratory.

“We are fortunate that things have been going well for us,” said N. Wayne Hale Jr., the manager of the shuttle program.

The additional spacewalks will be devoted to connecting the station’s power and cooling systems to the new module. Mission managers still are not sure that everything will be done in time for a Dec. 6 launching, but seem increasingly optimistic thanks to Commander Whitson and her crew, who have shown a determination to work ahead of the demanding schedule set for them and leave mission controllers on the ground struggling to match their pace.

“We have to put our sneakers on every day” to keep up with them, Mr. Todd said.

NASA has yet to resolve a serious problem that has emerged in recent months with one of the enormous rotary joints that helps solar panels to face the sun. The joint on the right side of the station is damaged, and an inspection during the last mission showed that the mechanism was peppered with metal shavings. The joint cannot be used until the problem is analyzed and fixed, and that cannot take place until next year, when replacement parts can be flown up and a plan of action devised.

Without the added power that the rotary joint helps the solar panels to draw, the station will not be able to support the power needs of the fully completed station — though it is not yet clear at what point that would become critical. A mission in February to bring up the first of two Japanese science modules could be the last before the power needs become acute.

“We’re still doing the analysis and sharpening our pencil,” Mr. Todd said.