The US Air Force's (USAF) unmanned, reusable space plane X-37B orbital test vehicle mission four (OTV-4) has successfully landed at Nasa’s Kennedy Space Center Shuttle Landing Facility in Florida.
In May 2015, the plane was launched for the fourth time aboard an Atlas V rocket from Cape Canaveral Air Force Station, Florida. The OTV-4 conducted experiments for 718 days during its mission, extending the total number of days spent on-orbit for the programme to 2,085.
X-37B programme manager lieutenant colonel Ron Fehlen said: "The landing of OTV-4 marks another success for the X-37B programme and the nation.
"This mission once again set an on-orbit endurance record and marks the vehicle's first landing in the state of Florida. We are pleased with the performance of the space vehicle and the data gathered to support the scientific and space communities."
Managed by the Air Force Rapid Capabilities Office, the X-37B programme performs risk reduction, experimentation and concept of operations development for reusable space vehicle technologies.
The programme's first mission, OTV-1, was launched in April 2010 and lasted for 224 days, while the second X-37B space plane spent 468 days in orbit following its launch in March 2011.
The third X-37B mission was launched in December 2012.
The USAF is preparing to launch the fifth X-37B mission from Cape Canaveral Air Force Station later this year.
Image: The USAF's X-37B Orbital Test Vehicle mission four lands at Nasa's Kennedy Space Center Shuttle Landing Facility, Florida. Photo: courtesy of the US Air Force.