Au revoir Cygnus !

After 72 days remaining docked to ISS, Cygnus spacecraft (S.S. Deke Slayton II, OA-4) left International Space Station and started its last flight. 

Mission finished, just like operational life of Cygnus OA-4. After 72 days being docked into Node-1 Nadir Common Berthing Mechanism (since 9 December 2015), it started today procedure of unberthing. Of course it could not do without proper preparation on the part of the crew. First step was performed by ISS crew member astronaut Tim Kopra, who sent commands to release bolts in Node-1 at 10:40 GMT. Next step performed from ground ROBO controllers, was sending commands to Canadarm robotic arm. It grabbed Cygnus at 11:28 GMT and moves it into safety distance from ISS; thanks to Canadarm preprogrammed commands, Cygnus was moved into correct position to start its last flight. From this moment Tim Kopra and Scott Kelly started to prepare for final part of the procedure. They set cameras for new positions and checked control panels. Cygnus was reconfigured for flight by turning on onboard navigation and flight control systems and was switched to onboard power supply. After opening unberthing window, after final confirmation from both NASA and Orbital ATK control centers, Tim Kopra and Scott Kelly started final phase of reattaching Cygnus. After releasing Canadarm's Latching End Effectors, Cygnus started its flight at 12:27 GMT. At 12:32 GMT Cygnus fired its engines to perform repositioning maneuver for reaching correct departure position. After that, Cygnus started to slowly move away from the ISS; shortly after 13:00 GMT it reached approach ellipsoid. From this point rest of deorbiting maneuvers will be performed with commands send from Orbital ATK Cygnus Mission Control Center located in Virginia. Reentry is scheduled for tomorrow, 20th February 2016 for 15:00 GMT - 19:00 GMT time range. Spacecraft will reenter over Pacific Ocean and burn in atmosphere with 1200 kg of trash from ISS.

On picture above: reentry of Cygnus on August 2014.

Cygnus OA-4 was launched on 6 December 2015 on atop of Atlas V rocket from launch site SLC-41 in Cape Canaveral and berthed to International Space Station on 9 December 2015. It is extended version of Cygnus - with increased to 27 cubic meters payload space; it delivered to ISS in its cargo module 3500 kg of supplies and science equipment. Cygnus delivered during this mission following payload:

  • 227 kg of equipment for Extravehicular Mobility Units
  • 847 kg of payload covered by Space Automated Bioproduct Lab (SABL)
  • NanoRacks container with nanosatellites
  • 1181 kg of supplies for crew members
  • 1007 kg different hardware for various maintenance and service of ISS
  • 87 kg of computer parts

For Orbital ATK and Cygnus it was fifth mission to ISS under Commercial Orbital Transportation Services signed with NASA on 23 December 2008 along with SpaceX.

Sources:
https://blogs.nasa.gov/spacestation/2016/02/19/cygnus-departs-station-after-robotic-release/