Astronauts on the International Space Station welcomed the arrival of a brand-new Russian module Thursday, an orbital room adds more research space and an extra parking spot for visiting spacecraft.

The unmanned module Poisk, which means "explore" in Russian, docked smoothly at a berth on top of the space station as they flew 222 miles over northern Kazakhstan in Asia.

"The arrival of this new module for the Russian segment went great," Russian cosmonaut Maxim Suarev radioed Mission Control in Moscow after the smooth docking. Suarev and fellow cosmonaut Roman Romanenko were poised to take remote control of the automated Poisk if the craft strayed off-course, but it flew true as expected.

The module docked at 10:41 a.m. EST, just four days ahead of NASA's own launch of the shuttle Atlantis to the orbiting laboratory. The six astronauts set to blast off on Atlantis Monday headed to NASA's Kennedy Space Center in Florida today to prepare for their upcoming flight.

Poisk launched Tuesday and is the first new Russian addition to the space station since the 2001 launch of the Pirs docking compartment, which is due to be discarded in 2011, NASA officials said. The space station has been under construction since 1998.

More station parking

Also known as the Mini-Research Module 2, Poisk can serve as a vital fourth Russian docking port for the station, as well as an airlock for Russian spacewalks. It can also be used as research space or as a storage room, astronauts have said.

The station now has five docking ports in all, one on the American side for visiting shuttles and four on the Russian segment to host crew-carrying Soyuz vehicles and unmanned cargo ships. Unmanned Japanese cargo ships can also be attached to berthing points on the station's American segment.

Because the space station's full crew increased to six people this year, two Soyuz spacecraft are required to be docked at all times to serve as ferries to Earth and emergency lifeboats. Before Poisk's arrival, that left only one remaining parking spot for cargo ships and other Soyuz vehicles bringing new crewmembers to the station.

Poisk's rooftop docking port should ease traffic concerns for flights to and from the station, NASA officials have said.

"Having four ports is a really big deal," NASA's deputy space station program manager Kirk Shireman told SPACE.com. "It gives us a lot of flexibility."

The Poisk module is just over 13 feet long, about 8 feet wide and weighs about 8,000 pounds. It has about 380 cubic feet of actual living space inside. The station room launched with about 1,764 pounds of cargo for the station's six-person crew.

NASA spokesperson Rob Navias said the supplies delivered aboard Poisk includes water supply gear, crew hygiene supplies, medical equipment, personal items and spare parts.

Spacewalk ahead

It will take some time before Poisk is ready to host visiting spacecraft or spacewalks.

First, the module's rocket engine section must detach in December to clear the top-mounted docking port. Russian cosmonauts will perform a spacewalk in January to outfit the port to accommodate spacecraft, then make the first docking later that month, mission managers said.

"It's going to be a new capability for us," Shireman said, adding that Soyuz crews will now be able to see the Earth behind the station when they dock at Poisk. "We'll have neat views of the station that we haven't seen before."

Poisk is one of three new Russian modules to be launched to the station over the next two years, NASA officials said. Its counterpart, the still-unnamed Mini-Research Module 1, will be delivered in May 2010 aboard NASA's shuttle Atlantis. Poisk launched first because it was ready earlier.

A much larger room, currently called the Multipurpose Laboratory Module, is slated to launch in 2011 to replace Pirs, NASA officials added.