Orbital ATK Cygnus S.S. John Glenn spacecraft finished its OA-7 mission on Sunday with destructive reentry performed week after successful unberthing from Unity Nadir berthing port.
Cygnus finished its lasting 43 days mission on Sunday. Vehicle was launched from the Cape Canaveral SLC-41 on the top of the Atlas V in enhanced configuration. Spacecraft delivered to ISS 3376 kg of payload on April 22, when it performed rendez vous and was grabbed and attached to Unity module by Canadarm2 robotic arm.
Undocking was planned for June 4 and begun from grabbing Cygnus by Canadarm2 two days earlier on June 2. Next phase was unlocking bolts of berthing port and moving it away using Canadarm2 at 11:05 UTC on June 6. Cygnus was taken few meters from Unity and released by robotic arm at 13:10 UTC. Next, it pulled out in front of the ISS using its thrusters. After another four hours Cygnus started to increase orbit and begun last phase of its mission.
Among two others payloads inside returning Cygnus OA-7, NASA placed their SAFFIRE-III experiment focused on research on physics of fire in low gravity conditions. Highly flammable cotton-fiberglass sample secured in container with sensors and cameras was ignited on Tuesday, June 6 at 21:17 UTC. Special fan pumped air on sample to let cameras record how flames are spreading in microgravity. Experiment was reported as success and Cygnus was ready for another objective.
Two main engine burned again on Thursday, June 8 and helped Cygnus in reaching orbit above course ISS of 476 km by 486 km (around 80 km above the Station). At 17:53 UTC and 21:03 UTC on Thursday, Cygnus deployed two pairs of Lemur-2 CubeSats for Spire Global. Satellites will provide maritime services and perform various research on atmosphere. All four satellites are representing latest generation among Spire Global’s constellation with planned operational life at two years, doubled comparing to previous generations. Created as 3U Cubesats (30 cm x 10 cm x 10 cm, 4 kg) are equipped with STRATOS (GPS radio occultation payload for measuring thickness of the atmosphere) and SENSE (Automatic Identification System payload).
On Saturday, June 10, control over Cygnus was transferred to Dulles, to Orbital ATK control center. Entering lower orbit begun with three burns of main engine at 15:50 UTC, 16:34 UTC and 17:20 UTC. Speed of the vehicle was reduced in total for 59 m/s; on Sunday, June 11, Cygnus was ready to start another burn as it was planned for 11:00 UTC. Lasting 689 s burn reduced speed for another 62.98 m/s. Reentry burn was performed at 16:36 UTC and finished after 330 seconds. At 17:12 UTC Cygnus entered atmosphere and after few minutes first remaining particles started to fall into Pacific Ocean. This particular moment was also end of last experiment performed by Cygnus during this mission. Special capsule with sensors known as RED-Data 2 with diameter of 9 cm and mass of 2.4 kg fall into ocean on parachute. It brought to Earth data recorded during destructive reentry – sensors were measuring such values like location, acceleration, temperature, pressure and body rates; such information are extremely valuable for creating model of break-up of the vehicle and creating model of dynamic of creating space debris during destructive reentries.