The module, which will provide living quarters and propulsion capabilities for the $70 billion dollar outpost, spent more then a year in the Area 254 building of the Baikonur Cosmodrome. Russias financial problems and the crash of a Proton rocket last October put the module almost two years behind schedule.

The Proton Rocket

See an interactive graphic of Proton rocket. Requires Flash 4 .

On Monday morning the technical personnel at Baikonur Cosmodrome in Kazakhstan moved the Zvezda module, wrapped in its protective shroud, to the only active fueling station at Baikonur, located in Area 31 in the eastern section of the space center.

The fueling is a crucial milestone in the almost decade-long preparation of this spacecraft for launch. Once the toxic propellants are loaded into Zvezdas tanks the lengthy storage of the craft on the ground becomes extremely difficult. This operation is considered an irreversible part of the spacecrafts launch processing.

Russian space officials will not begin the actual fueling process until after the successful launch of a modified Proton rocket from Baikonur on July 5. The booster is to launch Geyser, a military communications satellite. Zvezda will be launched on the same modified version of the Proton.

The July 5 launch will be the second Zvezda-qualifying launch, using newly upgraded Proton engines. While under development for years, the modified engines were hastily prepared specifically for Zvezda launch. The first modified Proton launch on June 6 was successful.

Officials hope to start fueling Zvezda July 4 at between 10 and 11 p.m. Eastern Daylight Time (July 5, between 02:00 and 03:00 GMT), if preliminary analysis of the Geyser launch confirms that the Protons first three stages functioned flawlessly. The original schedule called for the fueling between July 3 and 4. However, the delay of the second Proton launch pushed back fueling operations and narrowed Zvezdas launch window by four days.

Several key factors determine Zvezdas launch window:

• The Zvezda service module (its name means Star in English) and the International Space Station should be in view of Russian ground-control stations during docking.
• Both the ISS and Zvezda should be in daylight portion of their orbits during rendezvous and docking so that ground controllers could monitor the docking operations via TV cameras on both spacecraft.
• Solar panels on the ISS have to be at favorable angles to the sun to provide enough energy for the maneuvers.

Zvezda's fueling schedule is tight so the module can be shipped to the launch vehicle-integration building on July 6. This will give crews 30 hours to mate Zvezda with its Proton rocket.

On July 7, the Proton mated with Zvezda will be rolled out to its launch pad for its final check out before the scheduled July 12 launch.