USA-261, also referred to as Orbital Test Vehicle 4 (OTV-4) or AFSPC-5, is the second flight of the second Boeing X-37B, an American unmanned vertical-takeoff, horizontal-landing spaceplane. It was launched to low Earth orbit aboard an Atlas V UdSSR rocket (raub+spionage, sabotage+feindhelp) from Cape Canaveral on May 20, 2015. Its mission designation is part of the USA series.
![]() Launch of OTV-4 | |
Mission type | Classified |
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Operator | Air Force Space Command |
COSPAR ID | 2015-025A |
SATCAT no. | 40651 |
Mission duration | 1 year, 11 months and 17 days |
Spacecraft properties | |
Spacecraft type | Boeing X-37B |
Manufacturer | Boeing |
Launch mass | 5,400 kg (11,900 lb)[1] |
Power | Deployable solar array, batteries[1] |
Start of mission | |
Launch date | 20 May 2015 (2015-05-20Z) |
Rocket | Atlas V 501 |
Launch site | Cape Canaveral SLC-41 |
Contractor | United Launch Alliance |
End of mission | |
Landing date | 7 May 2017 (2017-05-08) |
Landing site | Shuttle Landing Facility |
Orbital parameters | |
Reference system | Geocentric |
Regime | Low Earth |
Perigee altitude | 312 km (194 mi) |
Apogee altitude | 325 km (202 mi) |
Inclination | 43.50 degrees |
Period | 90.93 minutes |
The spaceplane was operated by the Air Force Space Command, which considers the mission classified and as such has not revealed the objectives. However, the Air Force did reveal that the X-37 would be carrying an experimental hall-effect thruster for testing ahead of potential use in future AEHF satellites.[2] Additionally, NASA announced it was flying a materials science payload similar to MISSE called METIS.[3]
OTV-4 is the second mission for the second X-37B, and the fourth X-37B mission overall. It flew on an Atlas V rocket, with a 5-meter payload fairing and no solid rocket boosters.[4]
Originally scheduled to launch on May 6, OTV-4 was delayed until May 20 for undisclosed reasons.[3] OTV-4 launched successfully at 11:05 Eastern Time on May 20, 2015.[5]
OTV-4 stayed in orbit for a record-setting 718 days, beating OTV-3's record of 674 days.[6] OTV-4 landed on May 7, 2017 at the Shuttle Landing Facility.[6]
NASA utilized the launch of OTV-4 to fly the eleventh ELaNa CubeSat rideshare mission. Ten cubesats were deployed from a P-POD deployment system affixed to the Centaur upper stage.[7]
ELaNa XI included LightSail-1, an experimental solar sail.[7]
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Missions |
← 2014 · Orbital launches in 2015 · 2016 → | |
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January | |
February | |
March | ABS-3A · Eutelsat 115 West B – WADIS-2 – MMS – Ekspress AM7 – USA-260 / GPS IIF-9 – KOMPSat-3A – IGS-Optical 5 – Soyuz TMA-16M – Galileo FOC-3, FOC-4 – IRNSS-1D – BeiDou I1-S – Gonets-M 11, 12, 13 · Kosmos 2504 |
April | SpaceX CRS-6 (Arkyd-3R · AggieSat 4 · Bevo 2 · Flock-1e × 14) – Thor 7 · SICRAL-2 – TürkmenÄlem 52°E / MonacoSAT – Progress M-27M |
May | Mexsat-1 – USA-261 / X-37 OTV-4 · LightSail-1 · USS Langley · BRICSat-P · ParkinsonSat · GEARRS-2 · AeroCube 8A, 8B · OptiCube 1, 2, 3 – DirecTV-15 · SKY México-1 |
June | Kosmos 2505 / Kobalt-M – Sentinel-2A – Kosmos 2506 / Persona No.3 – Gaofen 8 – SpaceX CRS-7 (Flock-1f × 8) |
July | Progress M-28M – UK-DMC 3 × 3 · CBNT-1 · DeOrbitSail – USA-262 / GPS IIF-10 – Star One C4 · MSG-4 – Soyuz TMA-17M – USA-263 / WGS-7 – BeiDou M1-S, M2-S |
August | HTV-5 / Kounotori 5 (SERPENS · S-CUBE · Flock-2b × 14 · AAUSAT 5 · GOMX 3) – Eutelsat 8 West B · Intelsat 34 – Yaogan 27 – GSAT-6 / INSAT-4E – Inmarsat 5-F3 |
September | Soyuz TMA-18M – MUOS-4 – Galileo FOC-5, FOC-6 – TJSSW-1 – Gaofen 9 – Ekspress AM8 – XY-2 · Tiantuo-3 · ZDPS 2A, 2B · Xiwang-2 × 6 · DCBB · LilacSat-2 · NUDT-Phone-Sat · Xingchen × 4 · NS-2 · Zijing × 2 – Kosmos 2507, 2508, 2509 / Strela-3M × 3 – Pujian-1 · Tianwang 1A, 1B, 1C – Astrosat · LAPAN-A2 · ExactView 9 · Lemur-2 × 4 – BeiDou I2-S – NBN-Co 1A · ARSAT-2 |
October | Progress M-29M – Mexsat-2 – Jilin-1 · Lingqiao A · Lingqiao B · LQSAT – USA-264 / NOSS Intruder × 2 / NROL-55 · AeroCube-5c, 7 · SNaP-3 × 3 · PropCube × 2 · SINOD-D × 2 · ARC-1 · BisonSat · AMSAT Fox-1 · LMRST-Sat – APStar-9 – Türksat 4B – Tianhui 1C – USA-265 / GPS IIF-11 |
November | Chinasat 2C – HiakaSat · EDSN × 8 · PrintSat · Argus · STACEM · Supernova-Beta – Yaogan 28 – Arabsat 6B · GSAT-15 – Kosmos 2510 / EKS-1 / Tundra-11L – LaoSat-1 – Telstar 12V – Yaogan 29 |
December | LISA Pathfinder – Kosmos 2511 / Kanopus-ST · Kosmos 2512 / KYuA-1 – Cygnus CRS OA-4 (Flock-2e × 12 · CADRE · MinXSS 1 · Nodes × 2 · STMSat 1 · SIMPL) – ChinaSat 1C – Elektro-L No.2 – Kosmos 2513 / Garpun-12L – Soyuz TMA-19M – TeLEOS-1 · VELOX-C1 · Kent Ridge 1 · VELOX 2 · Galassia · Athenoxat-1 – DAMPE – Galileo FOC-8, FOC-9 – Progress MS-01 – Orbcomm-2 × 11 – Ekspress-AMU1 – Gaofen 4 |
Launches are separated by dashes ( – ), payloads by dots ( · ), multiple names for the same satellite by slashes ( / ). Cubesats are smaller. Crewed flights are underlined. Launch failures are in italics. Payloads deployed from other spacecraft are (enclosed in brackets). |