CAPE CANAVERAL, Fla. Russias Zvezda command module began a gradual 10-day climb toward the International Space Station on Friday after flight controllers pulled off a pair of orbital engine firings deemed crucial to an upcoming docking at the outpost.
An apparent problem with a docking target, meanwhile, is not expected to hamper the highly anticipated July 25 linkup at the now-vacant international station, officials said.
"That docking target is not required and will not have an impact on the rendezvous plan," NASA spokesman Kyle Herring said from the Russian Mission Control Center outside Moscow.
Flight controllers this week noted that a docking target designed to help pilots link spacecraft to the bus-sized Zvezda might not have deployed properly after the module was launched Wednesday from Baikonur Cosmodrome in Kazakhstan.
Data beamed back from Zvezda showed the targets arm-like boom swung away from the craft as planned after small explosive devices were fired to set it free. Still unclear, however, is whether the boom subsequently latched firmly in place.
"Sensors are not detecting the deployment of the docking target," Herring said.
About the size of a traffic sign, the target is a tool pilots would use to guide spacecraft up to Zvezda during final approach and docking.
The longstanding rendezvous plan, however, calls for Zvezda to dock automatically at the 7-story international outpost, and Herring noted the modules that make up the Mir space station all were linked together in the same fashion.
In a worst-case scenario, officials said a cosmonaut crew still could dock Zvezda with the station even if the docking target is not latched in place. A two-man cosmonaut crew has been trained to do pull off a manual docking if the automatic scheme fails.
The Zvezda module which will serve as a command post and living quarters for station construction and research crews is scheduled to dock with the international outpost at 8:56 p.m. Eastern Daylight Time July 25 (July 26, 00:46 GMT).
To that end, flight controllers fired Zvezdas twin orbital maneuvering engines twice today, boosting the module into an orbit with high and low points of 224 and 167 miles (361 and 269 kilometers), respectively.
Similar engine firings will be carried out over the next nine days as Zvezda closes in on the international station, which now is circling some 235 miles (376 kilometers) above the planet.
A series of tests to critical Zvezda systems, meanwhile, so far is proceeding without a hitch.
Said Herring: "All systems aboard the vehicle are in excellent shape."
A small space station unto itself, Zvezda is considered the key building block that will enable the United States, Russian and 14 other international partners to erect a 480-ton research complex that will span an area nearly as large as two football fields.
A successful July 25 docking will pave the way for a five-year flurry of stalled station construction flights and the arrival of the stations first full-time crew in November.
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