Cygnus OA-4

{{Short description|Late 2015 cargo mission to the ISS}}

{{Use American English|date=September 2020}}

{{Use dmy dates|date=May 2018}}

{{Infobox spaceflight

| name = OA-4

| image = OA-4 Cygnus AtlasV launch (2015-3497).jpg

| image_caption = An Atlas V 401 launches the S.S. Deke Slayton II.

| names_list = CRS OA-4
CRS Orb-4 (2008–2015)
Orbital-4 (2008–2015)

| mission_type = ISS resupply

| operator = Orbital ATK

| mission_duration = {{time interval|6 December 2015 21:44:57|20 February 2016 16:00|show=dhm|sep=,}}

| spacecraft = S.S. Deke Slayton II

| spacecraft_type = Enhanced Cygnus{{cite web|url=http://www.nasaspaceflight.com/2012/02/orbital-upbeat-ahead-of-antares-debut/|title=Space industry giants Orbital upbeat ahead of Antares debut|publisher=NASASpaceFlight.com|date=22 February 2012|access-date=31 May 2021}}

| manufacturer = {{Ubl|Orbital ATK|Thales Alenia Space}}

| launch_mass = {{cvt|7492|kg}}{{cite news|url=http://spaceflightnow.com/2015/11/29/international-space-station-and-crew-awaiting-atlas-5-launch/|title=International Space Station and crew awaiting Atlas 5 launch of Cygnus|publisher=Spaceflight Now|date=29 November 2015|access-date=2 December 2015}}

| payload_mass = {{cvt|3513|kg}}

| launch_date = {{Start date text|6 December 2015, 21:44:57|timezone=yes}}{{nbsp}}UTC (4:44:57{{nbsp}}pm{{nbsp}}EST)

| launch_rocket = Atlas V 401 (AV-061)

| launch_site = Cape Canaveral, SLC{{nbhyph}}41

| launch_contractor = United Launch Alliance

| disposal_type = Deorbited

| decay_date = {{End date text|20 February 2016, 16:00|timezone=yes}}{{nbsp}}UTC

| orbit_reference = Geocentric orbit{{cite web|url=http://www.n2yo.com/satellite/?s=41101|title=Cygnus ORB-4|publisher=N2YO.com|access-date=9 December 2015}}

| orbit_regime = Low Earth orbit

| orbit_inclination = 51.64°

| apsis = gee

| docking = {{Infobox spaceflight/Dock

| docking_target = ISS

| docking_type = berth

| docking_port = Unity nadir

| capture_date = 9 December 2015, 11:19{{nbsp}}UTC

| docking_date = 9 December 2015, 14:26{{nbsp}}UTC

| undocking_date = 19 February 2016, 10:38{{nbsp}}UTC{{cite news|url=http://www.americaspace.com/?p=91653|title=As OA-4 Cygnus Departs, Commercial Cargo Providers Prepare for Busy Visiting Vehicle Manifest|publisher=AmericaSpace|first=Ben|last=Evans|date=19 February 2016|access-date=20 February 2016}}

| release_date = 19 February 2016, 12:26{{nbsp}}UTC

| time_docked = {{time interval|9 December 2015 14:26|19 February 2016 10:38|show=dhm|sep=,}}

}}

| insignia = Orbital Sciences CRS Flight 4 Patch.png

| insignia_caption = NASA insignia

| programme = Commercial Resupply Services

| previous_mission = SpaceX CRS-7

| next_mission = OA-6

| programme2 = Cygnus flights

| previous_mission2 = Orbital-3

| next_mission2 = OA-6

}}

OA-4, previously known as Orbital-4, was the fourth successful flight of the Orbital ATK uncrewed resupply spacecraft Cygnus and its third flight to the International Space Station (ISS) under the Commercial Resupply Services (CRS-1) contract with NASA.{{cite web |url=http://spaceflightnow.com/launch-schedule/|title=Launch Schedule|publisher=Spaceflight Now|access-date=26 January 2015}}{{cite web|url=http://spider.seds.org/shuttle/iss-sche.html|title=International Space Station Flight Schedule|publisher=SEDS|date=15 May 2013}} With the Antares launch vehicle undergoing a redesign following its failure during the Orb-3 launch, OA-4 was launched by an Atlas V launch vehicle. Following three launch delays due to inclement weather beginning on 3 December 2015, OA-4 was launched at 21:44:57 UTC on 6 December 2015. With a liftoff weight of {{cvt|7492|kg}}, OA-4 became the heaviest payload ever launched on an Atlas V.{{cite news |url=http://spaceflightnow.com/2015/12/06/atlas-5-rocket-sends-cygnus-in-hot-pursuit-of-space-station/|title=Atlas 5 rocket sends Cygnus in hot pursuit of space station|publisher=Spaceflight Now|first=Justin |last=Ray|date=6 December 2015|access-date=7 December 2015}} The spacecraft rendezvoused with and was berthed to the ISS on 9 December 2015.{{cite news|url=http://spaceflightnow.com/2015/12/09/u-s-resupply-of-space-station-successfully-resumes/|title=U.S. resupply of space station successfully resumes|publisher=Spaceflight Now|first=Justin|last=Ray|date=9 December 2015|access-date=9 December 2015}} It was released on 19 February 2016 after 72 days at the International Space Station. Deorbit occurred on 20 February 2016 at approximately 16:00{{nbsp}}UTC.{{cite tweet |number=701100449634582530 |user=OrbitalATK |title=At ~11 am ET today, the S.S. Deke Slayton II #Cygnus reentered Earth's atmosphere over the Pacific, marking a successful end of mission. |author=Orbital ATK |date=20 February 2016 |access-date=20 February 2016}}