Cygnus OA-6 “Rick Husband” was unberthed yesterday from International Space Station and started its last task-Saffire experiment covering research on fire in low gravity conditions.
Unberthing finished lasting three month space journey of Orbital ATK Cygnus, which was part of the OA-6 resupply mission performed under CRS contract. Mission started from launching Cygnus on atop of Atlas V from Cape Canaveral on March 23, 2016. Cygnus docked to Unity berthing port on March 26, 2016 with over 3400 kg of supplies. Unberthing was scheduled for 13:30 GMT on 14 June 2016 with NASA astronaut Tim Kopra as operator of Canadarm2 robotic arm and controller of the process. Tim Kopra was cooperating with Mission Control Center in International Space Center in Houston, Texas along with Orbital ATK Control Center in Dallas, Virginia. Cygnus was packed with 2200 kg of disposable equipment, trash and Saffire experiment few days before unberthing. Final closing of the hatch was performed on June 13, 2016.
Yesterday in the morning at 10:00 GMT Tim Kopra depressurized Cygnus and flight specialists from Houston detached Cygnus from Unity nadir berthing port at 10:43 GMT. Since then Cygnus remained attached to ISS only with Canadarm2 which was operated remotely from Houston. Punctually 30 minutes before planned unberthing, Cygnus was already switched for internal power; Inside Cupola module of International Space Station Tim Kopra with Tim Peake (ESA) were waiting for final command from Houston to unberth Cygnus at 13:30 GMT. At 13:11 GMT Houston ordered to perform check of Cygnus for Tim Kopra. Two minutes after he reported about readiness for releasing Cygnus. At 13:27 GMT Cygnus was already at the end of extended Candarm2 robotic arm in correct position for release. Detaching was performed during fly over Paraguay at 13:30:34 GMT on altitude of 408 km and next at 13:34 GMT it performed first burn to reach safe distance from ISS. At 13:38 Cygnus passed 200 m distance where ISS crew is still able to send commands to Cygnus. From that moment it started to be under control of Orbital ATK Control Center.
Remaining under control of Orbital ATK Control Center in Dallas, Virginia, Cygnus will spent 8 days on orbit performing various experiments. Saffire experiment started about four hours after detaching and was confirmed by NASA around 20:00 GMT on June 14. Sample was placed in cargo trunk of Cygnus and contains mixture of cotton and fiberglass. It will be ignited by Orbital ATK Control Center and next it will be acting autonomously. Material is inside special container packed with sensors and cameras; results of the experiment will improve knowledge on space engineering and will help in developing safer spacecrafts in future. Cygnus will also deploy five Cubesats using Nanoracks for the first time in its history on 16th June, 2016 around noon. Next experiment will be performed just before its reentry. It will start and use Reentry Breakup Recorder (REBR), device designed for measuring acoustics and temperature which appear during breakup of Cygnus. Reentry to Earth atmosphere is planned for 11:45 GMT on 22nd June 2016. Impact zone for not burned pieces of Cygnus is planned for South Pacific.