Closing out a one-month stay at the International Space Station, a commercial Cygnus supply ship owned and operated by Orbital Sciences Corp. departed the huge orbiting complex Friday.

The Cygnus spacecraft just after release from the space station's Canadian-built robot arm Friday. Photo credit: NASA TV
 
The Cygnus spacecraft is scheduled to re-enter Earth's atmosphere over the uninhabited South Pacific Ocean on Sunday. The cargo ship is designed to disintegrate and burn up during re-entry, disposing of unneeded items and trash stowed inside by the space station's astronauts.

Under the control of engineers on the ground, the space station's 58-foot-long robotic arm pulled the Cygnus spacecraft away from a berthing port on the outpost's Harmony module at 5:14 a.m. EDT (0914 GMT), then maneuvered the spaceship to a release point about 30 feet below the complex.

European Space Agency astronaut Alexander Gerst, assisted by NASA flight engineer Reid Wiseman, took control of the robot arm and commanded it to release the Cygnus spacecraft at 6:40 a.m. EDT (1040 GMT).

Moments later, astronauts inside the space station sent commands for the Cygnus spacecraft to fire thrusters and fly away from the complex. It cleared the space station's "keep out" sphere, an imaginary safety zone around the outpost, a few minutes after separating from the robot arm.

The departure of the Cygnus spacecraft ends the second flight of the expendable Orbital-built freighter to the space station. The mission, known as Orb-2, launched July 13 aboard an Antares rocket from Wallops Island, Va.

Loaded with nearly 3,300 pounds of equipment, experiments and food, the spaceship completed a rendezvous with the space station July 16, when it was captured by the robot arm.

The mission is part of a $1.9 billion deal between NASA and Orbital for at least eight cargo deliveries through 2016.

Now filled with trash, the spacecraft will fly a safe distance from the space station before a pair of braking burns to guide it into a re-entry zone between New Zealand and South America.

Re-entry is scheduled for around 9:11 a.m. EDT (1311 GMT) Sunday.

The re-entry is timed to allow the crew on the space station to observe the spacecraft's fiery fall from space.

The crew's observations of Sunday's Cygnus re-entry is an exercise to prepare for the demise of Europe's ATV early next year.

Officials are considering putting the ATV on a trajectory for a "shallow" re-entry when it plunges back to into the atmosphere at the end of its mission.

Instead of lowering the craft's orbit to intersect the Earth's surface, controllers would put the low point of the ATV's orbit in the upper atmosphere, making for a slower warm-up and disintegration of the spacecraft. The shallow re-entry would also spread debris along a longer footprint.

The experiment would help NASA and its partners prepare for the disposal of the International Space Station at the end of its mission. A controlled re-entry of such a large vehicle -- roughly the size of a football field and weighing nearly a million pounds -- has never been attempted before.

The release and re-entry of Cygnus comes during a busy week for the space station's six-man crew. A European Automated Transfer Vehicle cargo craft docked to the lab's Russian service module Tuesday, and two Russian cosmonauts are gearing up for a spacewalk Monday.

The spacewalk's agenda includes the deployment of a small Peruvian satellite and the retrieval and installation of science experiments outside the Russian section of the space station.

Follow Stephen Clark on Twitter: @StephenClark1.