The U.S. military plans to land its secretive X-37B robotic space plane in California on Tuesday, thus ending its 22-month classified mission.
The time and date will depend on weather and technical factors, the Air Force said in a statement released on Oct. 10.
The X-37B space plane, also known as the Orbital Test Vehicle, blasted off for its second mission aboard an unmanned Atlas 5 rocket from Cape Canaveral Air Force Station in Florida back on Dec. 11, 2012, according to Reuters.
"Team Vandenberg stands ready to implement safe landing operations for the X-37B Orbital Test Vehicle, the third time for this unique mission," Colonel Keith Baits, 30th Space Wing Commander, said according to the Daily Mail.
The plane has been in space for a total of 672 days, far more than its previous flights, which lasted 225 and 469 days, respectively.
The experimental vehicle, which first flew back in April 2010, is 29-feet-long and resembles a mini space shuttle. It returned after eight months, according to Reuters.
A second vehicle blasted off in March 2011 and stayed in orbit for 15 months.
The vehicles, which were built by Boeing, are designed to test technologies, though details of the missions are "classified" according to the military statement.
The Air Force and NASA finalized a lease agreement last week to relocate the X-37B program from California to Florida's Kennedy Space Center.
"Kennedy is positioning itself for the future, transitioning to a multi-user launch facility for both commercial and government customers, while embarking on NASA's new deep-space exploration plans," Kennedy Space Center Director Robert Cabana said in a press release. "A dynamic infrastructure is taking shape, designed to host many kinds of spacecraft and rockets."
The military is looking into using the space shuttle's runaway for landing, but mentioned that the X-37B currently in orbit will touch down at Vandenberg Air Force Base in California, where the previous two missions also ended.
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