NASA space shuttle Atlantis has been officially cleared for July 8 launch to the International Space Station at 11:26 am EDT, which will be the final flight in the 30-year-old shuttle program.

The final shuttle launch countdown is set to start up at 1 pm on July 5, and fueling the external tank is slated to begin at about 2:11 am on July 8. The launch director, mission management team and NASA test director will conduct final polls for go/no go of space shuttle Atlantis on July 8 at 10:32 am EDT.

The launch date was announced Tuesday at the conclusion of a day-long flight readiness review at Kennedy Space Center in Florida. During the meeting, senior NASA and contractor managers assessed the risks associated with the mission and determined the shuttle and station's equipment, support systems and personnel are ready.

We had a very thorough review. This flight is incredibly important. The cargo that is coming up on this flight is really mandatory for space station, said Bill Gerstenmaier, assistant administrator for space operations.

The minimal crew consists of: Commander Christopher Ferguson, Pilot Douglas Hurley and Mission Specialists Sandra Magnus and Rex Walheim. The astronauts are scheduled to arrive at Kennedy on July 4 for their final launch preparations.

During the STS-135 mission, Atlantis will deliver the Raffaello multi-purpose logistics module filled with supplies and spare parts to sustain space station operations after the shuttles are retired.

Atlantis will deliver a year's worth of food, clothing, science equipment and supplies to the station, a $100 billion project of 16 nations that circles 220 miles above Earth, according to Reuters.

The mission also will fly the Robotic Refueling Mission, an experiment designed to demonstrate and test the tools, technologies and techniques needed to robotically refuel satellites in space - even satellites not designed to be serviced.

The crew also will return an ammonia pump that recently failed on the station. Engineers want to understand why the pump failed and improve designs for future spacecraft.

Atlantis is in great shape out at the pad. Team Atlantis is feeling good about the flow and the launch countdown and hope we'll be able to get her off the ground on Friday the 8th as scheduled, said Mike Leinbach, shuttle launch director.

Early morning Tuesday, an orbital debris -- commonly known as space junk -- threat impact interrupted the International Space Station's preparations for the last space shuttle's visit.

The six crew members of the space station were asked to take refuge in the station's two Russian Soyuz escape capsules. The station's crew divided into two groups of three and sealed themselves into the Soyuz capsules about 20 minutes before the object came closest to the station, which occurred at 8:08 am EDT.

In the station's history, this was only the second time that the crews had to seek shelter in their lifeboats for an orbital debris threat. Typically, the station maneuvers to avoid potential debris impacts, but the notice came just 14 hours before the closest approach, which was too late to plan and conduct an avoidance maneuver.

However, NASA has been trying to keep the Atlantis astronauts' training as simple as possible, as the four shuttle crew already are tasked to do the work of the six or seven people normally assigned to shuttle flights.

The U.S. space agency cut down the crew size to accommodate the smaller Russian Soyuz spacecraft that would be used to fly the Atlantis astronauts home in case the shuttle is too damaged to attempt landing.

NASA has had a second shuttle on standby, since the 2003 Columbia accident, for a rescue mission if needed. However, Atlantis is the 135th and last shuttle to fly, with no backup shuttle in waiting.

The United States is ending the shuttle program to save its $4 billion annual operating costs and use it to develop spaceships that can travel beyond the station, such as to the moon, asteroids and eventually to Mars.

Next year, Space Exploration Technologies and Orbital Sciences Corp. are scheduled to begin cargo deliveries to the station. NASA is hoping commercial companies will be able to fly astronauts as well, though those spaceships are not expected to be ready for at least four to five years.