Orbital ATK’s Cygnus spacecraft has unberthed from the orbiting International Space Station, marking the start of the second phase of its mission before re-entering Earth’s atmosphere.

Last month, the spacecraft was launched aboard an improved Antares rocket from Nasa Wallops Flight Facility, Virginia, US, to deliver around 2,400kg of cargo and science experiments to the astronauts.

The crew members have loaded the cargo module with around 1,120kg of items for disposal prior to Cygnus’ departure.

Currently orbiting on its own, Cygnus will conduct two secondary mission objectives as part of its flight programme, which includes the Spacecraft Fire Experiment-II (Saffire-II) payload experiment and the deployment of CubeSats to improve weather forecasting capabilities.

"We get another opportunity to showcase this unique spacecraft’s expanded capabilities beyond its core cargo delivery function."

Developed at Nasa’s Glenn Research Center, Saffire-II is the second in a series of tests to study the behaviour of large-scale fires in microgravity.

Orbital ATK space systems group president Frank Culbertson said: “Cygnus had a successful, month-long stay at the International Space Station, delivering critical cargo to the astronauts.

“Now, we get another opportunity to showcase this unique spacecraft’s expanded capabilities beyond its core cargo delivery function."

As part of the Saffire-II experiment, nine different experimental material samples will be used to ignite a fire inside Cygnus to help researchers better understand flammability of these materials in a microgravity environment.

The experiment will be conducted remotely from the ground and the resulting data will be downloaded via telemetry.

The spacecraft will also use a NanoRacks deployer to place various CubeSats into orbit to conduct meteorological research.

The OA-5 mission is scheduled for completion this Sunday when Cygnus is intended to burn up safely upon re-entering Earth’s atmosphere.

Image: Orbital ATK's Cygnus cargo spacecraft is seen from the Cupola module windows aboard the International Space Station. Photo: courtesy of Nasa.